WATER RESOURCE SUSTAINABILITY OF THE PALOUSE REGION: A SYSTEMS APPROACH

WATER RESOURCE SUSTAINABILITY OF THE PALOUSE REGION: A
SYSTEMS APPROACH
A Thesis
Presented in Partial Fulfillment of the Requirements for the
Degree of Master of Science
With a
Major in Civil Engineering
In the College of Graduate Studies
University of Idaho
by:
Ramesh Dhungel
December 2007
Major Professor: Fritz Fiedler, Ph.D., P.E.

ii
AUTHORIZATION TO SUBMIT THESIS
This thesis of Ramesh Dhungel, submitted for the degree of Master of Science with a major
in Civil Engineering and titled “Water Resource Sustainability of the Palouse Region: A
Systems Approach” has been reviewed in final form. Permission, as indicated by the
signatures and dates given below, is now granted to submit final copies to the College of
Graduate Studies for approval.
Major Professor Date
Fritz Fiedler
Committee
Members Date
Chuck Harris
Date
Erik R. Coats
Department
Administrator Date
Sunil Sharma
Discipline’s
College Dean Date
Aicha Elshabini
Final Approval and Acceptance by the College of Graduate Studies
Date
Margrit von Braun

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Abstract
The system dynamics approach was utilized for evaluating the sustainability of water
resources of the Palouse Region. The Palouse Basin, located on the border of Idaho and
Washington states, has three cities: Moscow, Pullman and Colfax. Water demand is
completely fulfilled by the groundwater aquifers. Two confined groundwater aquifers
systems exist, the upper Wanapum, and the lower Grande Ronde. These aquifers are located
within the basaltic Columbia River flows. The water levels of the Grande Ronde have been
declining up to 2 feet each year for more than fifty years. Study of these aquifers indicates
that there is likely to be a close relation between groundwater pumping and groundwater
depletion. This research was conducted to provide a broad synthesis of existing water
resources data, to understand the long-term implications of continued growth and water
demand on basin water resources, and to move towards sustainable management.
Demographic, hydrologic, geologic and economic data were collected and used to
develop systems models, comprised of population, hydrological and economical modules.
Water demand was forecasted by the population and demand components. Exponential
population growth was simulated with 1% annual growth for the entire Palouse Basin. The
hydrological component has groundwater and surface elements. In the Simple Model (SM),
groundwater of all regions was lumped into a single unit. In the Hydraulically Separated
Model (HSM), groundwater was divided into geological regions. A water balance at the land
surface was used to estimate recharge to the Wanapum. Leakage between the Wanapum and
Grande Ronde is allowed, and a range of recharge rates to the Grande Ronde is taken from
previously published estimates. A groundwater- surface water overlay was created to help
estimate recharge.

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Log-linear regression was used to find the relationship between the water demand and
several independent variables. Price elasticity of water demand of City of Pullman was
calculated. An economic module was developed from the regression equation with linear
extrapolation of the independent variables. Water demand was projected from the economic
module developed from the regression equation.
The water balance resulted in a mean areal precipitation of 71 centimeters,
evapotranspiration of 49 centimeters, runoff of 17 centimeters and recharge of 4.7
centimeters. The recharge from the water balance indicated a water level increase in the
Wanapum aquifer. The life of the aquifers depends on the initial volume of the aquifer and
recharge to the aquifer. The initial volume of the Grande Ronde is approximately 43 billion
gallons, and 1.6 billion gallons in the Wanapum, based on a storativity value of 10-3
. Under
the current conditions, the SM projected the life of the Wanapum to be more than 100 years,
while the Grande Ronde life ranged from a couple of years to more than 100 years. Using the
current infrastructure and published storativity values (10-3
to 10-5
), with no recharge
assumed to the Grande Ronde, the life of the Grande Ronde is simulated to be less than 20
years. Assuming one centimeter of recharge to the Grande Ronde added 30 years, and
assuming two centimeters added 100 years. The storativity was back-calculated with current
water extraction and water level decline rates to be 0.03. The back-calculated storativity
added 100 years to the life of the Grande Ronde. Because of the modeled hydraulic
separation among the groundwater regions, the HSM projects a comparatively shorter life of
the Moscow and Pullman Grande Ronde. So, if actual hydrological separation exists between
the groundwater regions, such separation may significantly affect water management of the
Palouse Basin.

v
To consider future water resources development, it was assumed that 80% of the
surface water can be potentially utilized. Paradise Creek was used for fulfilling Moscow’s
water demand, and the South Fork Palouse River for Pullman. In this applied water
management strategy, the surface water is able to fulfill water demand for the coming 100
years.
Regression results showed the price elasticity of water demand of marginal price is
inelastic while fixed price is elastic. The price elasticity of marginal price ranges from +1.6
to +2.97, indicating inelasticity. The exponents for median household income, fixed price and
precipitation had the expected signs in the regression equation. The developed economic
module projected a decline in water demand when the independent variables are assumed to
grow linearly over the coming 25 years.
A Sustainability Index showed that the Wanapum water use to be sustainable given
the present water use trend and infrastructure, while the Grande Ronde use was predicted to
be unsustainable.

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Acknowledgement
I would like to acknowledge my advisor Dr. Fritz Fiedler for his generous support.
This work would not have been possible with out his help and guidance. I am thankful to
Water of West (WOW) for the fund. I would like to thank Professor Chuck Harris and Dr.
Erik Coats for their continuous support and critical review of this thesis. I also want to thank
Dr. Erin Brooks, Professor John Bush, Dr. Ashley Lyman and Ms. Jennifer Hinds for helping
me understand different subject matters. I am thankful to all the staff and faculty member of
Department of Civil Engineering, Department of Statistics and writing center at University of
Idaho for their help to the completion of this thesis. I would like to thank City of Pullman,
City of Moscow and Washington State University for providing me supporting data for this
thesis.
I am grateful to my entire family member, specially my father and mother for their
support and inspiration, sister Rama and her husband Kailash, Rachana and her husband
Bikash, and my brother Ranjan for their help. Last but not the least, I am thankful to
colleagues, friends and the Nepalese community in Moscow that makes me feel home away
from home.

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Dedication
This thesis is dedicated to my parents Chandra Raj and Geeta

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Table of Contents
AUTHORIZATION TO SUBMIT THESIS............................................................................. ii
Abstract....................................................................................................................................iii
Acknowledgement ................................................................................................................... vi
Dedication............................................................................................................................... vii
Table of Contents...................................................................................................................viii
List of Figures.......................................................................................................................... xi
List of Tables .........................................................................................................................xiii
CHAPTER I.............................................................................................................................. 1
INTRODUCTION ................................................................................................................ 1
1.0 Overview..................................................................................................................... 1
1.1 Water Resource Management..................................................................................... 1
1.2 Overview of Study Area ............................................................................................. 2
1.3 Palouse Basin Management........................................................................................ 7
1.4 Background............................................................................................................... 10
1.5 Objectives ................................................................................................................. 13
CHAPTER II........................................................................................................................... 14
LITERATURE REVIEW ................................................................................................... 14
2.0 Overview................................................................................................................... 14
2.1 Water Resource Sustainability.................................................................................. 14
2.2 Water Balance Approach to Recharge...................................................................... 17
2.3 Previous Study of Recharge of the Palouse Basin.................................................... 19
2.4 Water Pricing and Price Elasticity of Demand ......................................................... 21
2.5 System Dynamics Approach..................................................................................... 23
CHAPTER III ......................................................................................................................... 27
DATA REQUIRED FOR MODELING............................................................................. 27
3.0 Overview................................................................................................................... 27
3.1 Watershed Map and Area.......................................................................................... 27
3.2 Geology of Palouse Basin Aquifer ........................................................................... 28
3.3 Aquifer Volume ........................................................................................................ 32
3.4 Precipitation Data for Hydrologic Model ................................................................. 35
3.5 Surface Runoff.......................................................................................................... 36
3.6 Evapotranspiration (ET)............................................................................................ 37
3.7 Recharge to Wanapum.............................................................................................. 38
3.8 Recharge to Grande Ronde....................................................................................... 39

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3.9 Water Demand and Per Capita Water Use................................................................ 40
3.10 Population and Growth Data................................................................................... 40
3.11 Economic Data........................................................................................................ 41
CHAPTER IV......................................................................................................................... 46
MODEL DEVELOPMENT SCENARIOS......................................................................... 46
4.0 Overview................................................................................................................... 46
4.1 Interactions among the Models................................................................................. 46
4.2 Population and Demand Forecast Model.................................................................. 48
4.3 Hydrological Model.................................................................................................. 49
4.4 Economic Module..................................................................................................... 58
4.5 Water Management Strategy..................................................................................... 61
4.6 Sustainability Index (SI) ........................................................................................... 65
CHAPTER V .......................................................................................................................... 67
RESULTS AND DISCUSSION......................................................................................... 67
5.0 Overview................................................................................................................... 67
5.1 Domestic Water Demand.......................................................................................... 67
5.2 Simple Model (SM) .................................................................................................. 69
5.3 Hydrologically Separated Model (HSM).................................................................. 88
5.4 HSM for Water Resource Management with Current Infrastructures...................... 93
5.5 HSM with Simple Economics................................................................................... 94
5.6 HSM with Surface Water.......................................................................................... 97
5.7 Surface Water.......................................................................................................... 106
5.8 Sustainability Index (SI) ......................................................................................... 108
5.9 Summary................................................................................................................. 110
CHAPTER VI....................................................................................................................... 112
CONCLUSIONS............................................................................................................... 112
6.0 Overview................................................................................................................. 112
6.1 System Dynamics Approach................................................................................... 112
6.2 SM and HSM .......................................................................................................... 113
6.3 Wanapum and Grande Ronde................................................................................. 113
6.4 Watershed Economics............................................................................................. 115
6.5 Sustainability of Aquifers ....................................................................................... 115
6.6 Calibration and Validations .................................................................................... 116
6.7 Data and Results Quality ........................................................................................ 117
6.8 Summary................................................................................................................. 118
6.9 Recommendations................................................................................................... 118

x
6.10 Limitations............................................................................................................ 122
REFERENCES ..................................................................................................................... 123
APPENDIX A....................................................................................................................... 129
Water Extraction Data of Four entities (1964-2005)........................................................ 129
APPENDIX B....................................................................................................................... 131
Comprehensive Data Set of City of Pullman for Economic Analysis.............................. 131
APPENDIX C....................................................................................................................... 134
Model Development Sections in STELLA Software........................................................ 134
APPENDIX D....................................................................................................................... 156
Equations in Stella ............................................................................................................ 156
APPENDIX E ................................................................................................................... 170
3D Projection of Palouse Basin Groundwater Surface Water Overlay ............................ 170

xi
List of Figures
Figure 1-1: Palouse Basin Watershed...................................................................................... 3
Figure 1-2: North Fork and South Fork Palouse River............................................................ 4
Figure 1-3: Groundwater Basin with Six Regions (Bush and Hinds, 2006)............................ 5
Figure 1-4: Water Extraction from Four Entities..................................................................... 7
Figure 1-5: Composite Hydrograph of Wells in the Palouse Basin....................................... 11
Figure 1-6: Water Level Fluctuation in Moscow Grande Ronde .......................................... 12
Figure 1-7: Water Level Fluctuation in Pullman Grande Ronde........................................... 12
Figure 2-1: Major Considerations in Water Resource Management ..................................... 15
Figure 2-2: Water Resources Balance (Miloradov, 1995)..................................................... 18
Figure 2-3: Components of STELLA Software..................................................................... 25
Figure 3-1: Schematic East West Cross Section of Study Area (Owsley, 2003) .................. 31
Figure 3-2: Definition Sketch for Calculating Volume of Water in the Aquifers ................. 33
Figure 3-3: Water Consumption and Marginal Price............................................................. 43
Figure 3-4: Monthly Water Consumption of Residential Sector of City of Pullman............ 44
Figure 4-1: Interaction between the Models.......................................................................... 47
Figure 4-2: Population Model................................................................................................ 48
Figure 4-3: Groundwater- Surface Water Overlay ................................................................ 50
Figure 4-4: Schematic of SM of the Palouse Basin............................................................... 52
Figure 4-5: Schematic of Connectivity in the HSM .............................................................. 54
Figure 5-1: Water Demand Projection of the Palouse Basin................................................. 68
Figure 5-2: Water Demand Projection of the Major Cities ................................................... 68
Figure 5-3: SM-1 ................................................................................................................... 71
Figure 5-4: SM-2 ................................................................................................................... 72
Figure 5-5: SM-3 ................................................................................................................... 72
Figure 5-6: SM-4 ................................................................................................................... 73
Figure 5-7: SM-5 ................................................................................................................... 74
Figure 5-8: SM-5 (Feet)......................................................................................................... 74
Figure 5-9: SM-6 ................................................................................................................... 75
Figure 5-10: SM-7 ................................................................................................................. 76
Figure 5-11: SM-8 ................................................................................................................. 77
Figure 5-12: SM-8 (Feet)....................................................................................................... 78
Figure 5-13: SM-9 ................................................................................................................. 79
Figure 5-14: SM-10 ............................................................................................................... 80
Figure 5-15: SM-10 (Feet)..................................................................................................... 80

xii
Figure 5-16: SM-11 ............................................................................................................... 82
Figure 5-17: SM-12 ............................................................................................................... 82
Figure 5-18: SM-13 ............................................................................................................... 83
Figure 5-19: SM-13 (Feet)..................................................................................................... 84
Figure 5-20: Wanapum Water Level Trend (Ralston, 2004)................................................. 85
Figure 5-21: HSM-1............................................................................................................... 89
Figure 5-22: HSM-2............................................................................................................... 89
Figure 5-23: HSM-2 (Palouse, Colfax and Viola)................................................................. 90
Figure 5-24: HSM-3............................................................................................................... 91
Figure 5-25: HSM-5............................................................................................................... 93
Figure 5-26: Moscow water management without surface water (HSM-4) .......................... 94
Figure 5-27: Linear Extrapolation of Independent variables for Regression Equation......... 95
Figure 5-28: Water Demand Projection by Economic Module............................................. 96
Figure 5-29: Water Extraction Pattern of Moscow (HSM-3)................................................ 98
Figure 5-30: Groundwater Volume in Moscow Region Aquifers (HSM-3) ......................... 99
Figure 5-31: Water Extraction Pattern of Moscow (HSM-4).............................................. 100
Figure 5-32: Groundwater Volume in Moscow Region Aquifers (HSM-4) ....................... 101
Figure 5-33: Water Extraction Pattern of Pullman (HSM-2) .............................................. 102
Figure 5-34: Groundwater Volume in Pullman Region Aquifers (HSM-2)........................ 103
Figure 5-35: Water Extraction Pattern of Pullman (HSM-4) .............................................. 104
Figure 5-36: Groundwater Volume in Pullman Region Aquifers (HSM-4)........................ 105
Figure 5-37: South Fork Palouse River Sub-Basins............................................................ 107
Figure 5-38: SI Grande Ronde (HSM-6)............................................................................. 109
Figure 5-39: SI Wanapum (SM-4)....................................................................................... 110
Figure 6-1: Future Schematic of SM of the Palouse Basin.................................................. 120

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List of Tables
Table 2-1: Estimated Recharge Rates (WRIA-34) ................................................................ 20
Table 3-1: Area of Sub-Watersheds....................................................................................... 28
Table 3-2: Aquifer Volume, Area and Thickness (Bush and Hinds, 2006)........................... 30
Table 3-3: Potential Groundwater Drawdown (PBAC, 1999)............................................... 34
Table 3-4: Surface Area of Wanapum and Grand Ronde Basalts (Bush and Hinds, 2006) .. 35
Table 3-5: Mean Areal Precipitation of Palouse Basin Sub-Watersheds .............................. 36
Table 3-6: Period of Availability of Daily Discharge of USGS Gauging Stations................ 36
Table 3-7: Mean Areal Surface Runoff of Palouse Basin Sub-Watersheds .......................... 37
Table 3-8: Mean Areal Evapotranspiration of Palouse Basin Sub-Watersheds..................... 38
Table 3-9: Mean Areal Recharge of Palouse Basin Sub-Watersheds.................................... 39
Table 3-10: Population of major cities................................................................................... 40
Table 3-11: Marginal and Fixed Price Rates of City of Pullman........................................... 42
Table 3-12: Sample Data for Economic Analysis of Single Family, Pullman, Washington . 45
Table 4-1: Components of Water Balance of SM.................................................................. 53
Table 4-2: Components of Water Balance of HSM............................................................... 56
Table 4-3: Initial Volume of Groundwater in Aquifers ......................................................... 57
Table 4-4: Annual Recharge to the Designated Wanapum Groundwater Regions................ 58
Table 4-5: Regression Coefficients for Price Elasticity Curve for Single Family................. 59
Table 4-6: Regression Coefficients for Price Elasticity Curve for Residential Households . 60
Table 5-1 : SM Applied Conditions....................................................................................... 70
Table 5-2: Summary Table of the Life of the Groundwater Aquifers ................................... 86
Table 5-3: Projection of Present Water Level Depletion Trend ............................................ 87
Table 5-4: HSM for Water Management ............................................................................... 88
Table 5-5: Summary of Management Strategies.................................................................... 97
Table 5-6: Summary Table of Life of the Groundwater Aquifers ....................................... 105
Table 5-7: Summary of Paradise Creek and South Fork Palouse at Pullman...................... 108
Table 5-8: Estimated Surface Water Availability (Stasney, 2006)...................................... 108

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CHAPTER I
INTRODUCTION
1.0 Overview
This chapter briefly discusses the general concept of water resources management
including the current water resource scenario of the Palouse Basin. The Palouse Basin, a
semi-arid area located along the border of northern Idaho and eastern Washington, is solely
dependent on groundwater for drinking water. The depletion of groundwater in the aquifers is
the major concern of this Basin. The background of this research is to analyze the water level
depletion of these aquifers, study the water use practice and recommend some future steps
for efficient water resource management. The major objective of this study is to use System
Dynamics Approach for evaluating and managing water resources of this basin.
1.1 Water Resource Management
Water resources can be managed primarily as surface water or groundwater or both
according to the geographic location and availability of water. In the United States, 74
percent of total public supply is provided by surface water during 1950 and 63 percent at
2000 with 11 percent decrease (Hutson et al., 2000). In comparison, 96 percent is fulfilled by
groundwater sources in Idaho (Anderson and Woosley, 2002). This indicates the increasing
trend of groundwater use in the public supply. Due to its widespread occurrence, generally
good quality and high reliability during droughts, the use of groundwater has increased
significantly in recent decades (Vrba and Lipponen, 2007). Because of scarcity and the
temporal unreliability of surface water resources in arid and semi-arid regions, the primary
source of drinking water is usually groundwater (Scanlon et al., 2006). But according to the
International Atomic Energy Agency (IAEA), much of the groundwater extracted in semi-

2
arid areas is “fossil water” (not recently recharged) and its use is not sustainable (Scanlon et
al., 2006). The combined utilization of surface water and groundwater can improve water
resources management in semi-arid regions.
For effective water resources management, it is necessary to understand the
interaction between groundwater and surface water. Efficient and sustainable management of
groundwater resources requires quantifying groundwater recharge (Khazaei et al., 2003).
Groundwater recharge can be broadly defined as the addition of water to a groundwater
reservoir (Vrba and Lipponen, 2007). In semi-arid areas, the variation of groundwater
recharge is typically significant in both space and time (Khazaei et al., 2003). Water tables
are often deep with localized (focused) recharge in semi-arid and arid areas, and there are
various mechanisms of recharge, such as infiltration from the beds of ephemeral streams, and
subsurface drainage from mountain areas through the alluvial material of valley beds
(Khazaei et al., 2003).
Due to the complexities of geologic formations and uncertainties in parameters such
as storativity (described subsequently), characterization of groundwater aquifers is
challenging. The most difficult component of the hydrologic budget is to quantify
groundwater recharge (Khazaei et al., 2003). So, the importance of recharge in the water
resources management is clear especially where groundwater is the major source of drinking
water. At this point, the important question is the estimation of the inflow, outflow and the
amount of stored water in an aquifer in particular spatial and temporal dimension.
1.2 Overview of Study Area
The Palouse Basin spans eastern Washington and northern Idaho. The major portion
is within Whitman County of Washington State, and Latah County of Idaho state, with a very

3
small area in Benewah County in Idaho. Figure 1-1 shows the Palouse Basin divided into six
sub-basins defined by United State Geological Survey (USGS) surface water gauging station
locations and state boundary (straight line at bottom).
Figure 1-1: Palouse Basin Watershed
The total area of the delineated watershed in this study is approximately 2,044 square
kilometers (km2
). The largest cities within the watershed are Pullman, Moscow and Colfax
while other smaller towns are Palouse, Princeton, Viola, Potlatch, Onaway, and Harvard. The

4
Palouse Region is a semi-arid area where precipitation ranges from approximately 59 to 85
centimeters per year (yr). With elevation increasing to the east, the precipitation of Palouse
Basin increases. The mean temperature of the Palouse Basin decreases from west to east. The
precipitation of the Palouse Basin is either in the form of rain or snowfall. The North Fork
Palouse River and the South Fork Palouse River are major rivers of this basin (Figure 1-2).
The sub-watersheds delineated from the South Fork Palouse River can be termed as South
Fork Palouse Basin Watershed and North Fork Palouse Basin Watershed from the North
Fork Palouse River. Paradise Creek, Missouri Flat Creek and Fourmile Creek are some other
streams in the watershed. The runoff in these rivers is influenced by the snow melting and
rainfall in the frozen ground in the spring seasons (Palouse Basin Community Information
System, 2007).
Figure 1-2: North Fork and South Fork Palouse River
(Source: Palouse Basin Community Information System, 2007)
According to the geographic variations, the groundwater regions are divided into
Palouse, Colfax, Viola, Pullman, Moscow and Uniontown regions (Figure 1-3). The

5
uppermost layer of the Palouse Basin is composed of loess which is basically a deposit of
wind-blown silt. According to the dominant geologic formations, there are two groundwater
aquifers in the Palouse Basin, identified as the Wanapum (WP) and Grande Ronde aquifers
(GR). The composition of these aquifers is more than 60 percent basalt, with the rest being
sediments including silt, clay and sand. Both Wanapum and Grande Ronde are confined
aquifers (Larson et al., 2000).
Figure 1-3: Groundwater Basin with Six Regions (Bush and Hinds, 2006)

6
The Wanapum aquifer is the shallower of the two at approximately 110m deep and
the Grande Ronde aquifer at approximately 290m. These thicknesses (depth) represent the
potential depth of water extraction in these confined aquifers. The “2000 Annual Report
Water Use in the Palouse Basin” reports that water levels of these aquifers have been
decreasing up to 2 feet annually (McKenna, 2001) for seventy years (Robinschon, 2006,
PBAC, 2006). By 1923, the water level of the Wanapum aquifer had dropped to
approximately 13.4 meters below the surface and about 30.5 meters below the surface water
by 1957(Bloomberg, 1959).
The shallower Wanapum aquifer is the primary water supply for rural residents of
Latah County within the basin limits and in some areas of Whitman County (McKenna,
2001) and supplies approximately 32 percent Moscow’s drinking water (Ralston, 2004,
PBAC, 2006). Approximately 70 percent of Moscow’s and 100 percent of Pullman’s
drinking water demand is fulfilled by the lower Grande Ronde aquifer. These aquifers have
satisfactory groundwater quality for domestic, agricultural and industrial purposes. Also,
these aquifers have been the subject of much research over the last 40 years.
The total population of the area is about 51,000 people. The population within 7 miles
of Moscow and Pullman is denser compared to rest of the regions (i.e., Colfax, Viola and
Palouse). The decreasing level of groundwater in these aquifers, and thus its sustainability, is
a major concern of basin residents. If we review the water use pattern of the City of Moscow,
in 1964, 560 million gallons of water was extracted from City of Moscow pumping stations
and 820 millions gallons in 2005, a 46 percent rise. Figure 1-4 shows the trend of water use
by four major entities (i.e., City of Pullman, City of Moscow, University of Idaho and
Washington State University) from 1964 to 2005 (Appendix A).

7
0
200
400
600
800
1000
1960 1970 1980 1990 2000
Years
WaterExtraction(MillionGallons)
Pullman
Washington
State University
University of
Idaho
Moscow
Figure 1-4: Water Extraction from Four Entities
1.3 Palouse Basin Management
Several organizations and social groups have been working in this basin for some
time. Among them are the Palouse Basin Aquifer Committee (PBAC), Palouse Conservation
District, the Palouse Water Conservation Network and Protect Our Water. All essentially
have the common goal of sustainable use for water in the aquifer. Few studies are carried out
about the surface water utilization of this Basin. A feasibility study was carried by Stevens,
Thompson, and Runyan in 1969 for utilizing surface water for the drinking water supply in
Pullman-Moscow area (McKenna, 1999). The study suggested construction of a pipeline
from the Palouse River at Laird Part in Latah County, or from the Snake River at Wawawai
County Park in Whitman (Stevens et al., 1970). At present, the use of surface water as an
additional supply is getting attention because of the threat of the groundwater scarcity in this
region.
The PBAC was formed in the late 1960s to address declining water levels in the
regional aquifers. It is a voluntary, cooperative, multi-jurisdictional committee comprised of

8
representatives from seven entities: University of Idaho (UI), Washington State University
(WSU), Pullman (Washington), Colfax (Washington), Moscow (Idaho), Whitman County
(Washington), and Latah County (Idaho). PBAC is guided by an intergovernmental
agreement signed by the stakeholder representatives. The Washington Department of
Ecology (WDOE) and the Idaho Department of Water Resources (IDWR) also have signed
an agreement with the committee. The purpose of the PBAC is to provide a forum for
stakeholders to address resource issues in the watershed, particularly by supporting research
to clarify the current situation of water resources in the basin and by considering possible
actions that members could take.
The management of the Palouse Basin was initiated in the 1960s. A significant effort
has been devoted to accelerate effective planning in the 1990s by implementing a Plan of
Action by PBAC. The major goal of the Plan of Action was to use the groundwater without
depleting the basin aquifers and protecting quality of water (PBAC, 1992). This Plan of
Action was the beginning action plan of all stakeholders of PBAC for the management of
groundwater with an attempt to limit the annual aquifer pumping that increases to one
percent of the pumping volume based on a five year moving average starting in 1986 (PBAC,
1992). The current stated mission of PBAC is to provide a long term, quality water supply
for the Palouse Basin by balancing basin wide water supply by 2020 (PBAC, 2006). PBAC
has developed a 20-Year Plan of the management of aquifer adopted in 2000 which is an
attempt to stabilize the declining groundwater levels in the deep Grande Ronde aquifer by the
year 2020. Furthermore; an important goal for achieving the above mission is to develop an
alternate water supply plan by 2010.
Water Resource Inventory Area (WRIA) 34 planning unit is composed of local and

9
state organizations of Washington and includes the state of Idaho as a voting member. Latah
County, Idaho, is included in the WRIA planning unit. Washington State watershed planning
process includes the following four phases. The first phase is an organization, second
assessment, third planning and final implementation. The Phase II level 1 is the phase of
compilation and reviewing of the existing data of the watershed. Level 2 of the Phase II is the
phase of collecting new data and level 3 is the long term monitoring of selected parameters
for improving management strategy. The planning phase should maintain the coordination
process, divide responsibilities, regulate and figure out funding sources. The planning phase
also provides the base for the implementation phase for managing water resources. It should
address the water resources management issues of agriculture, commercial, industrial and
residential sector including stream flow water.
The “Phase II-Level 1 Technical Assessment for the Palouse the Basin, Water
Resource Inventory Area (WRIA-34)” is an important study to address the management
aspect of the watershed that was prepared for the Palouse Planning Unit. Technical
requirements of the Watershed Planning Act (RCW 90.82) are fulfilled by this study. RCW
90.82, signed by the twelve state agencies in Washington, supports local government, interest
groups and citizens to manage water resources in WRIA areas. The key issues defined by
WRIA-34 of the Palouse Basin are future water availability (including some water rights
issues), concerns about water level decline in the Grande Ronde aquifer in the Pullman-
Moscow area and water quality concerns. Another important issue is to maintain cross-state
coordination with Idaho.

10
1.4 Background
The historical and on-going decreasing water level in the aquifers, particularly in the
Grande Ronde, is the major concern in the Palouse Basin, as this indicates unsustainable use.
Figure 1-5 shows the composite hydrograph of different wells in the Wanapum and Grande
Ronde aquifers in the Palouse Basin. The top section is the Palouse loess followed by the
Wanapum aquifer and the Grande Ronde (Figure 1-5). Figures 1-6 and 1-7 show the water
level fluctuation patterns of the Moscow and Pullman Grande Ronde wells. The apparent
depletion of groundwater level has the potential to create a scarcity of high quality drinking
water. Fluctuations in groundwater level might not simply and solely be indicative of
groundwater recharge and extraction, however. The naturally occurring changes in climate
and anthropogenic activities can contribute to long term fluctuations in groundwater level
over periods of decades (Healy et al., 2002). Due to the temporal variability of
evapotraspiration, precipitation, and irrigation, seasonal fluctuations in groundwater levels
are common in many areas. Phenomena like rainfall, pumping, barometric-pressure
fluctuations create seasonal fluctuations in groundwater levels (Healy et al., 2002). In the
year 1990, the City of Moscow reduced its dependence on Grande Ronde. From then,
approximately 70 percent of water was extracted from the Grande Ronde and the rest from
the Wanapum. But Pullman still is solely dependent in the Pullman Grande Ronde and there
has been constant depletion of the water level in the aquifer up to now.
The gradual increase in population and infrastructure development in Palouse Region
likely will lead to a further increase in water demand. But the declining groundwater level
raises the possible scarcity of drinking water in Palouse Region. So, the people residing in
this area are compelled to study groundwater in these aquifers and manage in a sustainable

11
manner according to the future need. The dependence on groundwater may be reduced by
using surface water, or it may be possible to use groundwater in a sustainable manner. The
primary goal of this research is to develop a model that provides a framework to study
sustainability and management of water resources of the Palouse Basin, synthesizing
available information and data using the “System Dynamics Approach” described in section
2.5.
Figure 1-5: Composite Hydrograph of Wells in the Palouse Basin
(Source: Leek F., 2006)
Figure 1-5 shows the groundwater level trend of the aquifers from the year 1923 to
2003. Figure 1-6 shows the long term hydrographs of Moscow and University of Idaho (UI)
wells.

12
Figure 1-6: Water Level Fluctuation in Moscow Grande Ronde
Figure 1-7 shows the long term hydrograph of Pullman and Washington State
University (WSU) wells.
Figure 1-7: Water Level Fluctuation in Pullman Grande Ronde
(Source: Leek, Wu, Bush, Qiu and Keller, 2005)

13
Both figures (1-6 and 1-7) show the water level is depleting in the Grande Ronde
aquifer.
1.5 Objectives
The overarching goal of this research is to develop a systems model to study water
resources sustainability of the Palouse Basin. The major objectives of this study are:
1. To estimate the quantity of surface and groundwater resources of the Palouse Basin at
particular temporal and spatial scales using available data and common calculation
methods;
2. To develop a water balance using these estimates and a systems model to simulate the
balance;
3. To link the developed water balance with estimates of demand, using population
growth and simple economics using systems modeling;
4. To use the model to explore sustainability and select management approaches; and
5. To conduct limited sensitivity analyses of the model to select parameters and various
future water use scenarios in the Palouse Basin.

14
CHAPTER II
LITERATURE REVIEW
2.0 Overview
This chapter is a review of literature on topics related to the water resources
management. The beginning section of this chapter discusses the concept of water resource
sustainability and sustainability index (SI). As recharge is one of the important components
of groundwater, water balance approach for calculating recharge is discussed. Some earlier
studies about the recharge computation of the Palouse Basin are also tabulated. The
relationship between the price and water demand is discussed in the section of the price
elasticity of water demand. And finally, the System Dynamics Approach and its use in water
resource planning and management is described.
2.1 Water Resource Sustainability
Creating balance between water demand and available water resources can be broadly
defined as sustainable water resources management (Simonovic et al., 1997). One definition
of sustainability states that “Sustainable water resource systems are those designed and
managed to fully contribute to the objectives of the society, now and in the future, while
maintaining their ecological, environmental, and hydrological integrity” (ASCE, 1998). The
“non-excessive” use of surface water, “non-depletive” groundwater abstraction, and
“efficient” re-use of treated wastewater are considered to be sustainable practices (Xu et al.,
2002). The Sustainable Water Resource Roundtable (SWRR) defines water use sustainability
as the ratio of water withdrawn to renewable supply (SWRR, 2005). The major
considerations for sustainable water resource management can be seen in Figure 2-1. Water
resource management is not only about the technical aspects of water demand and supply.

15
Sustainable management includes environmental, legal, social, economical and hydrological
aspects of water resources.
Figure 2-1: Major Considerations in Water Resource Management
Portland Basin, similar to the Palouse Basin, located across the Columbia River into
Southern Washington and Northern Oregon is also dependent on the deep aquifers for
regional water supply. Regional aquifer management of the Portland Basin purposed induced
recharge to decrease aquifer drawdown and increase sustainability of long-term groundwater
use (Koreny and Terry, 2001). It is not always easy to quantify the term sustainability but
there are several techniques available, such as sustainability indexes (SI) and indicators. The
ratio of water deficit relative to the corresponding supply can be defined as SI (Xu et al.,
2002). A 2002 article by Xu et al. used the approach where demand greater than 80 percent
of potential water supply was (arbitrarily) classified as vulnerable on the SI. Equation 2-1
shows how Xu defined the SI when supply is greater than demand and vice versa.
Environmental
Hydrologic
EconomicSocial
Legal

16
{






≤
>−
=
DS
DSSDS
SI
,0
,/)(
(2-1)
where, D is the water demand and S is the available water-supply, in any consistent units.
There are numerous groundwater resource sustainability indicators published by
UNESCO (Vrba and Lipponen, 2007) in the report titled “Groundwater Resources
Sustainability Indicators.” In the context of the Palouse Region, understanding these
groundwater indicators has particular importance. The Groundwater Sustainability Indicator
(GSI) and Groundwater Depletion Indicator (GDI) are discussed briefly. In semi-arid areas,
to calculate GSI (Equation 2-2), the average annual abstraction and recharge values should be
used (Vrba and Lipponen, 2007). Three different scenarios were developed according to
abstraction and recharge conditions.
%100*
TGR
TGA
GSI = (2-2)
where, TGA is the total groundwater abstraction and TGR is the total groundwater recharge
Groundwater Scenario 1: abstraction ≤ recharge; (i.e., < 90 percent)
Groundwater Scenario 2: abstraction = recharge; (i.e., = 100 percent)
Groundwater Scenario 3: abstraction > recharge; (i.e., > 100 percent)
Groundwater Scenario 1 indicates that the groundwater is not fully utilized and this
sector is yet to be developed. Groundwater Scenario 2 is a developed condition whereas
Groundwater Scenario 3 is over exploitation of groundwater. Another groundwater
sustainability indicator in groundwater systems is the Groundwater Depletion Indicator
(GDI). GDI is defined as the ratio summation of areas with a groundwater depletion problem
to the total studied area in percentile.

17
2.2 Water Balance Approach to Recharge
The percolation of water from the unsaturated zone to the subjacent saturated zone is
broadly defined as recharge (Dingman, 2002). In humid regions, the occurrence of recharge
is expected in topographic highs and discharge in topographic lows. But in arid regions, it
generally occurs in topographic lows (Scanlon et al., 2002). Vegetation plays an important
role in the recharge phenomenon. Three classes of techniques are used for calculating
recharge; physical, tracer and numerical. Physical methods such as those employed in water
balances are indirect methods of recharge calculation. Tracer methods using chemical,
isotopic and gaseous tracers are direct methods of recharge calculation (Xu and Beekman,
2003). Numerical models are generally used to calculate recharge rates over larger areas
(Scanlon et al., 2002), and rely on solution of mechanistic or empirical equations, such as
Richards’ equation.
Water balance techniques are fundamental to water resource analysis. In sustainable
water management plans, a water balance is an essential element (Miloradov, 1995). In this
study, the water balance method is used to calculate recharge, and the results of the water
balance are used to form the basis of the systems dynamics model of the basin. Two water
balance approaches can be conceived, the basic water balance and the water resources
balance approach based on Miloradov, 1995. In the basic water balance approach, there is no
mechanism to collect lost water, but in the water resource balance approach, lost water can
be collected and reused again. The difference between the water balance and water resource
balance as described is the potential for human interaction in the water balance: re-use and
redistribution of lost water back to the watershed in the form of either surface water or
groundwater. Figure 2-2 shows the water resource balance approach.

18
Figure 2-2: Water Resources Balance (Miloradov, 1995)
Water balance methods are based on the principle of conservation of mass. For an
arbitrary control volume over a given period of time, the difference between total input and
output will be balanced by the change of water storage with the volume (Equation 2-3).
StorageinChangeOutflowInflow =− (2-3)
Equation 2-4, after Sokolov and Chapman, (1974), shows the major inflows and outflows
components of water balance approach.
0=−∆−−−−++ ηSQQETQQP UOSOUISI (2-4)
The term P represents precipitation, QSI and QUI represent the surface and sub-surface
water inflow within water body from outside, QSO and QUO represent the surface and sub
surface water outflow from water body, ET is the evapotranspiration within the water body,
∆S is change in storage and η is the discrepancy (error) term. To simplify the analysis
presented here, the subsurface inflow and outflows is assumed to be zero for all scenarios
considered in this research. Equation 2-5 shows a general form of water balance approach
used in this study.
RQETP s =−− (2-5)
where, Qs is the discharge of river (surface water inflow) and R is the recharge.
Water
available
for use
Precipitation
Runoff
Surface Waters
Groundwaters
Additional water
available for use
Lost water

19
The water balance approach is an indirect method of calculating recharge. In the
absence of direct measurements, the estimation of recharge by water balance models is the
best available tool (Faust et al., 2006). The major limitation of the water balance approach is
the dependence of one component to other (i.e., accuracy of recharge depends on the
accuracy of other components of water balance; Scanlon et al., 2002). Because of this
limitation, the usefulness of water balance methods in arid and semi-arid regions is
questioned by many researchers (Scanlon et al., 2002), primarily because of the uncertainty
in the estimation of evapotranspiration. In water balance approach, evapotranspiration is
typically more difficult to accurately quantify than precipitation and stream-flow and is large
in comparison to the magnitude of recharge.
2.3 Previous Study of Recharge of the Palouse Basin
PBAC has incorporated the studies related to the Palouse Basin in its website.
Recently, the Palouse Basin Community Information System has compiled information
related to the Palouse Basin. Several studies have been carried out to estimate recharge of the
Palouse Basin. The recent studies conducted by UI graduate students are Murray, 2002; and
O’ Geen, 2002. Results showed that 33 percent loess covered area has less than 0.3
centimeters per year recharge rate and 37 percent area with homogeneous loess has 1
centimeter per year (O’Geen, 2002). These loess cover represents the uppermost layer of the
Palouse Basin. Recharge estimates are tabulated in Table 2-1.

20
Table 2-1: Estimated Recharge Rates (WRIA-34)
Recharge Rate
Name
(cm yr-1
)
Palouse Loess
Stevens, 1960 3.0
Johnson, 1991 10.5
Muniz, 1991 2.5 to 10.3
O’ Brien and Others, 1997 (Pullman) 0.2 to 2
O’Geen, 2002 0.3-1
Wanapum
Foxworthy and Washburn, 19631 1.6
Barker, 1979 19.7
Smoot, 1987 9.15
Fealko and Fiedler, 2006 (Median) 8.5
Grande Ronde
Foxworthy and Washburn, 1963 1.6
Crosby and Chatters, 1965 Negligible
Barker, 1979 1.70
Smoot, 1987 4.83
Lum and others, 1990 5.08
Larson, 2000 Negligible
Not motioned (Wanapum or Grande
Ronde)
Bauer and Vaccaro, 1989 7.11 (Current)
Bauer and Vaccaro, 1989 10.42 (Pre-development)
Lum and others, 1990 7.11 (Total)
Baines, 1992 4.5
Bauer and Vaccaro, 1990 3.8
The recharge estimation of the Wanapum aquifer by Fealko, 2003 in the Pullman-
Moscow area is about 8.5 centimeters per year. Fealko used water balance approach applied
to the Paradise Creek Watershed to calculate these recharges. The isotope dating of the
groundwater of the Grande Ronde aquifer conducted by Kent Keller and others indicates the

21
age of the water as 10,000 years old (O'Brien et. al., 1996; Larson et. al., 2000).
2.4 Water Pricing and Price Elasticity of Demand
This study includes the computation of price elasticity of water demand of the City of
Pullman. Water pricing is an important aspect of water resources economics and planning.
Flat rate, constant rate and block rate are three commonly used water pricing structures. A
single price for an unlimited amount of water use is a flat price where fixed price for each
unit of water use is constant price (Dzisiak, 1999). The price per unit of water changes as the
volume consumed moves into different categories in the block rate structure (Dzisiak, 1999).
The relationship between changes in water price to change in quantity of water used is
defined as price elasticity of water demand (Mays, 2005). Price elasticity can be further
defined as a measure of the willingness to use more water when water price falls or
conversely give up when water price rises (Young, 1996). There is an inverse relation
between water pricing and consumption. Generally, the price elasticity of water demand is
calculated using regression analysis with several independent variables and water use as the
dependent variable. Commonly included independent variables are median household
income, average household size, precipitation, and average water price. Due to the limited
availability of data, often household size must be estimated indirectly from population and
number of dwellings (Martinez-Espiñeira, 2002). Either annual or seasonal precipitation
values can be used in regression equation for calculating price elasticity of water demand.
Seasonal precipitation is generally taken as the summer period because of high fluctuation in
demand, use and availability. Five months, generally from May to September, are often used
as summer period. Foster and Beattie (1979) included precipitation variable during those
months where average monthly temperature was at least 45o
F and 60o
F in the northern and

22
southern regions of the United States respectively. Water demand is directly proportional to
temperature and inversely related to precipitation (Cook et al., 2001). In the summer, more
water is needed for irrigation if there is inadequate precipitation to maintain vegetation. If
precipitation is abundant, then the coefficient of precipitation is anticipated to be negative.
Study conducted by Linaweaver et al. (1967) use evapotraspiration in place of precipitation.
Available moisture or moisture defined by difference between the precipitation and
evapotranspiration can be used as alternative variables for precipitation. The common
exponential form of regression equation for calculating price elasticity of water demand is
shown in Equation 2-6.
43210
**** XXXX
r
X
HPIPeQ = (2-6)
After taking log to the both sides, Equation 2-6 can be written as Equation 2-7. It is a
log linear empirical equation (Equation 2-7) used to model price elasticity of demand.
)ln(*)ln(*)ln(*)ln(*)ln( 43210 HXPXIXPXXQ r ++++= (2-7)
where, Q is the quantity of water consumption, Pr is water price, I is the median household
income ($ per year), P is the commutative precipitation (inch per year), H is the average
household size (number of people per household). X0 to X4 are the unknown least square
coefficients that should be estimated. IWR-MAIN, Water Demand Management Suite, has
used the following equation to calculate the predicted water use (Equation 2-8).
7654)3)((21 dddddFCdd
RTHDHeMPaIQ = (2-8)
where, Q is the predicted water use in gallons per day, I is median household income
($1000’s), MP is effective marginal price ($ / 1000 gal), e is base of the natural logarithm,
FC is fixed charge ($), H is mean household size (person per household), T is maximum- day
temperature (degrees Fahrenheit), R is total seasonal rainfall (inches), a is intercept in

23
gallons/day and d1 to d7 are elasticity values for each independent or explanatory variable.
For a continuous demand function, price elasticity of water demand (ε) is calculated
by comparing the change in the quantity demanded (dQ) to the change in price (dPr)
(Equation 2-9).
)(*
r
r
dP
dQ
Q
P
=ε (2-9)
where, ε is the price elasticity of demand, Pr is the average water price, Q is the quantity of
water demand, dQ is the change in demand and dPr is the change in price.
2.4.1 Price elasticity in the Palouse Basin and nearby Cities
Lyman (1992) used a dynamic model to study water demand of City of Moscow.
Using number of climatic variables, price and income determinants and household
characteristics with survey data, peak and off-peaks effects were analyzed in water demand.
The price elasticity of seasonal demand for residential water is -0.65 for winter (off-peak)
and -3.33 for summer (peak) in Moscow, ID (Lyman, 1992).
Both short term and long term elasticity of marginal price is -0.3 in the Lewiston
Orchards Irrigation District (Rode, 2000). But the results for the marginal price, fixed price
and income variables are not statistically significant in entire City of Lewiston (Rode, 2000).
An effort to study dynamic aggregate water demand model for the Palouse Region (City of
Moscow and Pullman) by Peterson S.S., 1992 was inconclusive due to the insignificant
marginal variable (Rode, 2000).
2.5 System Dynamics Approach
In the 1950s, the System Dynamics Approach was initiated by J. W. Forrester at
Massachusetts Institute of Technology. Nonlinear dynamics form the general basis of

24
System Dynamics Approach (Ahmad and Simonovic, 2004). This approach can also be used
for shared vision planning. Shared vision planning involves discussion and debates as part of
the comprehensive decision making process (Stephenson, 2002). The emphasis of the shared
vision model is participation of stakeholders and technical experts together in a collaborative
planning process. Interactions between stakeholders and experts make complex feedback
mechanisms, similar to the natural feedback mechanisms in nature, and those between the
natural world and humans. For example, as water supplies diminish, the price of water tends
to increase, which reduces demand on the natural system.
Because of these numerous components and complex feedback mechanisms, it is
difficult to perform a sensitivity analysis using focused physical models. Sensitivity of
complex systems can be more readily explored using the systems approach. Xu et al. (2002)
emphasizes that difficulties mainly arise from the integration of social perspectives with the
technical elements. Results from more detailed and focused physical models can and should
inform system model development.
A basic challenge associated with any kind of modeling is to encapsulate the essential
aspects of real world phenomenon in the model. System modeling approach can be simple
enough for beginners who do not have the expertise required in other modeling efforts. The
approach facilitates understanding of the behavior of complex systems over time from causal
loop diagrams and stock and flows. Widely available systems software has user friendly
interfaces in which it is easy to develop and explain models. These types of models are
excellent for cause and effect analysis (sensitivity analysis) simulation. Because of these
factors, the System Dynamics Approach can be used as a useful tool in shared vision
planning, and facilitates interaction between experts with different disciplinary backgrounds.

25
Commercially available system dynamics software includes AnyLogic, Powersim,
Studio, CONSIDEO, Vensim, STELLA and iThink, MapSys, and Simile. STELLA Version
9 was used for developing the models in this study because of its solid reputation and wide
use. There are four basic model components in the STELLA software: stocks, flows,
converters and connecters. Stocks are able to accumulate or deplete things (such as
groundwater reservoirs) over time. It is a state variable which helps to define the state of
system. Flows control the changes of magnitude of stocks, and can be viewed as inputs and
outputs to stocks. Converters have a wide range of functions such as holding external factors
affecting stocks and flows (e.g., growth rates), data, numerical constants, equations and
graphical relationships. Finally, connecters are used for transferring information between
model components. Information can be transferred among all components with connecters
except for stocks (the storage in which are completely controlled by flows). Ghost
components help to make replicas, aliases, or shortcuts for individual stocks, flows, and
converters. Model boundaries are represented in STELLA by clouds. Source cloud is infinite
source of inflow and sink cloud is infinite sink for outflow. Figure 2-3 shows the basic
components of STELLA.
Stock
Inflow Outflow
Converter
Source Cloud Sink Cloud
Connecter
Figure 2-3: Components of STELLA Software

26
Use of the System Dynamics Approach in water resources planning accelerated in the
1990s. Some of the important works in this approach in water resource planning were
drought studies (Keyes and Palmer, 1993), modeling sea-level rise in a coastal area (Matthias
and Frederick, 1994) and river basin planning (Palmer, 1998; Ahmad et al., 2004).
Simonovic et al., (1997) used the System Dynamics Approach for planning and policy
analysis for the Nile River Basin in Egypt. Simonovic and his colleagues further applied this
approach in flood prediction, control and damages calculation, hydropower generation and
climate changes sectors. System Dynamics approach is used for community based water
planning in the Middle Rio Grande in north-central New Mexico (Tidwell et al., 2003). Dr.
Richard Palmer, Professor of Civil and Environmental Engineering, University of
Washington has developed the “Fairweather” model in the STELLA software as an example
for his students. “Fairweather” model integrates several aspects of watershed management,
such as hydrology, population dynamics, demand forecast, river rafting, economic metrics,
water supply, and water laws.

27
CHAPTER III
DATA REQUIRED FOR MODELING
3.0 Overview
The watershed map defines the boundary of surface water systems. Hydrologic and
demographic data are required in this study. The hydrologic data for the surface water
systems are the mean areal precipitation, evapotraspiration and runoff. For groundwater
hydrology, the potential groundwater drawdown and storativity (for confined aquifers) are
required with recharge rate to the aquifers. Watershed area is required to compute the total
surface water and groundwater. The demographic data (population, per capita water use,
median household income, and average size of the household) are needed to calculate the
price elasticity of water demand. The precipitation data and price of water are also needed for
price elasticity of water demand.
3.1 Watershed Map and Area
A Geographic Information System (GIS) was used to delineate the surface watershed
based on 10 meter resolution Digital Elevation Map (DEM) of Palouse Basin. Colfax (i.e.,
USGS gauging station 13346100, Palouse River at Colfax, WA) was taken as the
downstream point for delineating watershed. Five more USGS gauging stations were used for
delineating sub-watersheds. The area of watershed map developed from the GIS was
compared to USGS gauging stations data and results were found to be satisfactory. The total
area of the delineated watershed is 2,044 square kilometers (Table 3-1).

28
Table 3-1: Area of Sub-Watersheds
Area of Sub-
Watersheds (Local
Area )
USGS Gauging
Stations
Site Name
(km2
)
13349210
Palouse River below South Fork at Colfax
(Entire Basin)
2,044
13345000 Palouse River near Potlatch, ID 816.36
13345300 Palouse River at Palouse, WA 69.77
13346100 Palouse River at Colfax, WA (North Fork) 388.45
N/A1
South Fork above Colfax, WA (local) 439.03
13346800 Paradise Creek at UI at Moscow, ID 45.65
13348000 South Fork Palouse River at Pullman, WA 284.35
Total 2,044
1. No USGS gage exists on the South Fork of the Palouse upstream of Colfax. The stream flows were
computed as the difference between USGS gauge 13346100, downstream of the confluence of the South Fork
and the main stem of the Palouse River and USGS gage 13348000 located on the main stem of the Palouse
River just upstream of the confluence near Colfax.
3.2 Geology of Palouse Basin Aquifer
The geology of an aquifer helps to understand the spatial extent and characteristics of
the aquifer material matrix, its hydrological and geological separation and volume.
Numerous research activities have been carried out to understand the geology of the Palouse
Basin within the last thirty years. John Bush and his colleagues from University of Idaho and
Washington State University have led these efforts. The geology of the Palouse Basin is
highly complex and therefore it is difficult to understand the groundwater basin. According
to John Bush and his colleagues, the Palouse Basin aquifer can be divided into six regions
determined in part by geologic variations, and in part by information availability. They are
Moscow, Pullman, Colfax, Viola, Palouse and Uniontown (Figure 1-3). It is important to
note that the division of the basin into these regions does not imply hydrologic connections
or lack thereof.
The Palouse Basin lies within the Columbia River Basalt Group (CRBG). The uppermost

29
layer of the Palouse loess ranges from 0 to 76 meters (PBAC, 1990). Groundwater in the
Palouse loess is in unconfined state (Foxworthy and Washburn, 1963). As previously
discussed, there are upper and lower aquifers in the basin. The existence of the upper
Wanapum aquifer seems significant in all groundwater basins with comparatively thin layer
in Pullman area (46 meters) (Bush and Hinds, 2006). The Moscow Wanapum is productive
for groundwater extraction whereas the Pullman Wanapum is unproductive (Leek, 2006).
The hydrologic and geologic characteristics of the Grande Ronde also vary within the
different groundwater basins. The Grande Ronde of Pullman and Moscow region appears as
a confined aquifer (Fealko, 2003, Holom, 2006). But Bandon and Osiensky, 2007 mentioned
that the vicinity of Moscow Well 2 (located in the Wanapum aquifer) is not confined. The
Uniontown groundwater region is outside the designated surface water watershed area and
not accounted to any computation in this study. Table 3-2 shows the estimated volume, areas
and thickness of groundwater regions. It should be noted that the confidence in these
estimates varies greatly depending on available information with the best estimates being
near population centers. Figure 3-1 shows the schematic of the geology of the aquifers and
the locations of wells.

30
Table 3-2: Aquifer Volume, Area and Thickness (Bush and Hinds, 2006)
Average
Wanapum
Thickness
Average
Grande
Ronde
Thickness
Wanapum
Volume
Grande Ronde
Volume
Wanapum
Area
Grande
Ronde
Area
Name of
Groundwater
Regions
(m) (m) (m3
) (m3
) (km2
) (km2
)
Moscow 137 259
1.12E+10
Sediments-60%
Basalt-40%
1.66E+10
Sediments-
65%
Basalt-35%
81.75 63.94
Pullman Upper
Grande Ronde
(productive)
46 305
1.15E+10
Sediments-5%
Basalt-95%
7.20E+10
Sediments-
10%
Basalt-90%
252.08 235.97
Pullman Lower
Grande Ronde
+ Imnaha1
305
3.60E+10
Lower Grande
Ronde +
Imnaha
Sediments-
10%
Basalt-90%
Viola 137 244
3854050289
Sediments-45%
Basalt-55%
5185964728
Sediments-
65%
Basalt-35%
28.08 21.25
Palouse 85 152
1.62E+10
Sediments-35%
Basalt-65%
1.13E+10
Sediments -
60%
Basalt-40%
190.12 74.32
Colfax 122 244
4.22E+10
Sediments-5%
Basalt-95%
8.10E+10
Sediments-5%
Basalt-95%
346.06 332.13
Uniontown 122 457-549
9.44E+10
Sediments-15%
Basalt-85%
3.17E+11 to
4.19E+11
(no wells, only
outcrops along
snake river)
782.71 763.86
Uniontown
Saddle
mountain
46
3.57E+10
Sediments-30%
Basalt-70%
1.Imnaha is lowermost layer of the Columbia Basin Basalt Group.

31
Figure 3-1: Schematic East West Cross Section of Study Area (Owsley, 2003)

32
3.3 Aquifer Volume
Porosity is the volume of water storage per volume of aquifer in an unconfined
aquifer. Likewise, the storage coefficient or storativity is volume of water storage per volume
of aquifer in a confined aquifer (White and Revees, 2002). Both the Wanapum and Grande
Ronde aquifers are confined; the storativity is thus used for calculating volume of water in
the aquifers. By definition, storativity is the volume of water that an aquifer releases per unit
surface area under a unit decline of hydraulic head. Alternatively, storativity is the ratio of
volume of water in confined aquifer to volume of aquifer (Equation 3-1).
AquiferofVolume
AquiferConfinedinWaterofVolume
SyStorativit =)( (3-1)
White (2002) computed volume of groundwater in New Zealand by using average saturated
thickness (Equation 3-2).
cofficientstorageaverageaquiferofareathicknesssaturatedAverageVolume **= (3-2)
Storativity of the Palouse Basin Grande Ronde ranges between 10-3
and 10-5
based on
aquifer discharge tests (Osiensky, 2006). A base value of 10-3
was used in the model, with an
allowed range from 10-2
to 10-5
. The lowering of the groundwater level near the pumping
well is defined as drawdown (Mullen, 2007). The average potential groundwater drawdown
in the current infrastructure was calculated as a difference between the approximate pumping
water level and the pump intake elevation in the wells (Figure 3-2). There is also wide
variation in the thickness of the Wanapum and Grande Ronde regions. So, geometrical
methods (i.e., average potential drawdown depth, surface area) are used for calculating
groundwater volume in these aquifers. The average maximum potential groundwater
drawdown is computed at the bottom of the well. Potential maximum groundwater
drawdown data were obtained from the four entities (Table 3-3).

33
Well
Static water level,
Pumping level
Bottom of pump
Bottom of well
Figure 3-2: Definition Sketch for Calculating Volume of Water in the Aquifers
Equation 3-3 was used to calculate volume of water in aquifers in the Palouse Basin.
HASV ∆= ** (3-3)
where, V is the volume of water in aquifer, S is the storativity, ∆H is the water level change
used in computing the volume and A is the surface area of aquifer. The total groundwater
volume of the aquifer is calculated from the average saturated depth. ∆H, the potential
drawdown, is used calculate the volume of the groundwater which is smaller than the total
saturated thickness of the aquifer. The potential groundwater drawdown of Colfax, Palouse
and Viola are assumed to be similar to the Pullman groundwater region.
current drawdown
potential drawdown
maximum
potential drawdown
saturated
thickness

34
Table 3-3: Potential Groundwater Drawdown (PBAC, 1999)
Pumping
Water Level3
Depth of the
Pump Intake
Potential
Drawdown
(Pumping Level
to Pump Intake)
Depth of
Bottom of
Well3
Potential
Drawdown
(Pumping Level
to Bottom of
Wells)
Wells No
(ft) (m) (ft) (m) (ft) (m) (ft) (m) (ft) (m)
Moscow Wanapum
Moscow 2 66 20 170 52 104 32 240 73 174 53
Moscow 3 67 20 135 41 68 21 569 173 502 153
UI 5 130 40 247 75 117 36
UI 6 140 43 351 107 211 64
UI 7 137 42 350 107 213 65
Average 86 26 Average 243 74
Moscow Grande
Ronde
Moscow 6 342 104 450 137 108 33 1305 398 963 294
Moscow 8 376 115 473 144 97 30 1458 445 1082 330
Moscow 9 314 96 440 134 126 38 1242 379 928 283
UI 3 317 97 1337 408 1020 311
UI 4 290 88 747 228 457 139
Pullman Grande
Ronde
Pullman 3 83 25 167 51 84 26
Pullman 4 92 28 932 284 840 256
Pullman 5 95 29 712 217 617 188
Pullman 6 170 52 560 171 390 119
WSU 11
- 247 75
WSU 31
109 33 223 68 114 35
WSU 42
117 36 165 50 48 15 276 84 159 48
WSU 62
289 88 405 123 116 35 702 214 413 126
WSU 72
157 48 365 111 208 63 1814 553 1657 505
WSU 82
331 101 631 192 300 91 812 248 481 147
1. Wells no longer use
2. Pumping water level measured at August 2007 (Source: WSU)
3. Pumping water level (PBAC, 1999)
It should be noted that these average potential groundwater drawdown values were
calculated according to the present available data, current pumping levels, depth of pump
intake and depth of well. They will vary according to the water level change in the
groundwater. The area of groundwater regions were calculated from the estimated volume

35
and thickness of the aquifer provided by John Bush and his co-workers from Department of
Geology, University of Idaho (Table 3-4).
Table 3-4: Surface Area of Wanapum and Grand Ronde Basalts (Bush and Hinds, 2006)
Wanapum Area Grande Ronde Area
Name
(km2
) (km2
)
Moscow 81.75 63.94
Pullman 252.08 235.97
Viola 28.08 21.25
Palouse 190.12 74.32
Colfax 346.06 332.13
Total 898.09 727.61
3.4 Precipitation Data for Hydrologic Model
Precipitation is an important hydrologic phenomenon and affects every aspect of
water resources. Precipitation is used for calculating recharge in the water balance approach.
Areal mean precipitation was computed for each of the six sub-basins over the 1971 to 2000
time period (consistent with widely available climate normals). The Parameter-elevation
Regressions on Independent Slopes Model (PRISM) precipitation maps, developed by
Oregon State University, of girded data with 30-arcsec (800m) were used in this analysis.
The highest precipitation value within the watershed is approximately 85 centimeters (cm) in
the Palouse River sub-basin above Potlatch Idaho, while the lowest value of approximately
59 centimeters is observed at South Fork above Colfax, Washington. The mean areal
precipitation over the entire watershed is approximately 71 centimeters. Table 3-5 shows the
mean areal precipitation of each sub-watershed (local areas).

36
Table 3-5: Mean Areal Precipitation of Palouse Basin Sub-Watersheds
PrecipitationUSGS
Gauging
Stations
Site Name
(cm)
13349210 Entire Basin 70.9
13346100 Palouse river at Colfax, WA (North Fork) 59.3
N/A South Fork above Colfax, WA (local) 58.9
13345300 Palouse river at Palouse, WA 66.7
13346800
Paradise Creek at University of Idaho at Moscow,
ID
75.1
3.5 Surface Runoff
Surface runoff is used in the water balance approach. Daily discharge data (1971-
2000) from USGS gauging stations were used to calculate surface runoff. Table 3-6 shows
USGS gauging stations with missing daily discharge data and the USGS gauging stations
used to fill the missing daily discharges. Missing data were estimated with linear regression
among the USGS gauging stations.
Table 3-6: Period of Availability of Daily Discharge of USGS Gauging Stations
Stations
(Y)
Site Name
Stations used
for filling gap
(X)
Linear Regression
Equation
Period of
Availability
13349210 Entire Basin 13345000
y = 1.3951x + 22.83,
R2
= 0.8916
1963/10/01-
1995/09/30
13345300
Palouse River at Palouse,
WA
13345000
y = 1.0381x + 1.54,
R2
= 0.9708
04/19/1973-
10/02/1980
13346100
Palouse River at Colfax,
WA (North Fork)
13345000
y = 1.0798x + 13.60,
R2
= 0.9352
10/1/1963-
05/31/1979
13346800
Paradise Creek at UI at
Moscow, ID
13348000
y = 0.2032x - 0.29,
R2
= 0.719
10/01/1978-
09/30/2006
13348000
South Fork Palouse river
at Pullman, WA
13346800
y = 3.5385x + 10.11,
R2
= 0.719
02/01/1934-
09/30/2006

37
Table 3-7 shows the estimated runoff of each sub-watershed. The highest mean areal
surface runoff is approximately 29 centimeters (cm) in the Palouse River near Potlatch Idaho,
while lowest value of 5 centimeters is observed in the Palouse River at Palouse, Washington.
The mean areal runoff over the entire watershed is approximately 17 centimeters.
Table 3-7: Mean Areal Surface Runoff of Palouse Basin Sub-Watersheds
Surface RunoffUSGS
Gauging
Stations
Site Name
(cm)
13346800
Paradise Creek at University of Idaho at Moscow,
ID
16.4
3.6 Evapotranspiration (ET)
For calculating evapotranspiration, land use maps1
, soil maps2
, elevation maps3
and
PRISM maps4
were used. A Lapse rate of 3.5 degrees per 305 meters (1000 feet) was used
for the calculation. The daily precipitation and temperature data were taken from Moscow.
The potential evapotranspiration was calculated using the Hargreaves approach. Some more
weather stations were added that would only change the frequency of storms without
changing the total amount. The estimation of evapotranspiration followed the prediction
methodology by the Thornthwaite and J.R. Mather approach. Thornthwaite - Mather is a
lumped model where the entire watershed is treated as a single unit and soil water status is
tracked through time. Specific parameters used in this method are rooting depth, available
soil water storage depth, crop coefficient and maximum canopy storage amount. Table 3-8

38
shows the estimated evapotraspiration of each sub-watershed.
1. Land use Map reference: University of Idaho (UI) Library, U.S. Geological Survey, 20000329, Multi-
resolution Land Characterization for Idaho: University of Idaho library, Moscow, Idaho (30m resolution).
2. Soils Map: Soil Survey Geographic (SSURGO) Database, U.S. Department of Agriculture, Natural
Resources Conservation Service, 20060109 Fort Worth, Texas (30 m resolution),
URL:<http://www.ftw.nrcs.usda.gov/ssur_data.html>
3. Elevation Map: U.S. Geological Survey (USGS), EROS Data Center 1999, National Elevation, Dataset,
raster digital data Sioux Falls, SD (30 m resolution), http://gisdata.usgs.net/ned/>
4. PRISM maps (1971-2000) 800 m resolution,
http://www.ocs.oregonstate.edu/prism/products/viewer.phtml?file=/pub/prism/us_30s/grids/tmax/Normals/us_t
max_1971_2000.14.gz&year=1971_2000&vartype=tmax&month=14&status=final
Table 3-8: Mean Areal Evapotranspiration of Palouse Basin Sub-Watersheds
EvapotranspirationUSGS
Gauging
Stations
Site Name
(cm)
13346800 Paradise Creek at University of Idaho at Moscow, ID 49.8
The highest mean areal evapotraspiration is approximately 54 centimeters (cm) in the
Palouse River near Potlatch ID, while lowest value of approximately 45 centimeters is
observed in the South Fork above Colfax, Washington (North Fork). The mean areal
evapotraspiration over the entire watershed is approximately 49 centimeters.
3.7 Recharge to Wanapum
The recharge rate to the Wanapum aquifer is of primary importance. At present, even
though the major portion of water is extracted from the Grande Ronde, the recharge to

39
Wanapum represents the total amount of water that reaches to the groundwater basins. The
recharge rate to the Wanapum aquifer was calculated following Equation 2-5, using the basic
water balance approach over the 1971 to 2000 time period. Table 3-9 shows the recharge to
the entire Palouse watershed and the corresponding sub-watersheds.
Table 3-9: Mean Areal Recharge of Palouse Basin Sub-Watersheds
Precipitation
ET
(Brooks,
2006)
Runoff
(Fiedler, 2006)
Recharge
Site Name
USGS
Gauging
Stations
(cm) (cm) (cm) (cm)
Entire Basin 13349210 70.9 49.0 17.2 4.7
Palouse River at Colfax,
WA (North Fork)
13346100 59.3 45.2 7.7 6.4
South Fork above
Colfax, WA (local)
N/A 58.9 44.8 10.4 3.7
Palouse River near
Potlatch, ID
13345000 84.7 53.8 29.2 1.7
Palouse River at
Palouse, WA
13345300 66.7 46.6 4.9 15.2
Paradise Creek at
University of Idaho at
Moscow, ID
13346800 75.1 49.8 16.4 8.9
South Fork Palouse
River at Pullman, WA
13348000 66.1 46.7 10.2 9.2
The average recharge rate to the entire watershed is 4.7 centimeters per year, varying
from 1.9 to 15.2 centimeters per year. The recharge computed in this study (Table 3-9) is
within the range of previous studies. The lowest value of recharge by Foxworthly and
Washburn (1963) is 1.6 centimeters and 19.7 centimeters per year as highest value by Baker
(1963).
3.8 Recharge to Grande Ronde
The Grande Ronde is commonly thought to receive little recharge. This assumption
is supported by aquifer water age dating (Crosby and Chatters, 1965 and Larson et al., 2000).
However, other researchers (Table 2.1) argued and calculated the existence of recharge from
Wanapum to Grande Ronde. The recharge rate to the Grande Ronde is assumed to be

40
between 0 and 2 centimeters per year herein (except for the projection of present water level
trend) as it is beyond the scope of this work to assess the validity of the Grande Ronde
recharge estimates.
3.9 Water Demand and Per Capita Water Use
At present, Pullman area extracts 100 percent of their water from Grande Ronde. The
Moscow area extracts 70 percent of their water from the Grande Ronde and 30 percent from
the Wanapum. As the Palouse Region is not highly industrialized, the per capita water use is
not readily available in different sectors like residential, commercial and industrial. Average
per capita water use data provided by PBAC was used in the model. In the year 2000, PBAC
estimated approximately 160 gallons per person per day water use in the Palouse Basin.
3.10 Population and Growth Data
Population data were obtained from the United States Census Bureau and cities
sources. Table 3-10 shows the population of cities within the basin.
Table 3-10: Population of major cities
The annual population growth varies from 1 to 2 percent (City of Moscow, 1999) in
Moscow and almost same in Pullman. So 1 to 2 percent rise in population growth is used to
represent the entire Palouse watershed. A base population growth rate of 1 percent was used
in the model and allowed to range from 1 to 5 percent.
City Population Year
Pullman 25,262 US Census of Bureau ,2005
Moscow 21,862 US Census of Bureau ,2005
Colfax 2,880 City of Colfax, 2007
Viola 622 2007
Potlatch 791 2007
Total 51,197

41
3.11 Economic Data
The residential price elasticity of water demand of the City of Pullman was
calculated. Because of the limited availability of these data across the basin, the city of
Pullman was taken as representative of the basin, and used to develop a single price elasticity
relationship. The City of Pullman is the largest population center in Palouse Basin. Single
family, total residential families and total population are three economic scenarios for
calculating price elasticity of water demand. Total residential households includes single,
duplex, multiple, group and mobile homes. These water consumption estimates did not
include the industrial, commercial and schools and offices.
The independent variables for price-elasticity of water demand includes precipitation,
annual household income, average household size, marginal water price, and fixed water
price; whereas the monthly water use is dependent variable. Median household income in
dollars, marginal and fixed price in dollars, precipitation data in inches and household size
are the independent variables. In the Economic Scenario 1, the dependent variable is monthly
water use by single family per household per 100 cubic feet whereas in Economic Scenario 2,
monthly water use per household per 100 cubic feet by total residential sector. Finally, in
Economic Scenario 3 the dependent variable is mean monthly household water use by the
total population. Equation 3-4 shows the water use per household per 100 cubic feet of single
family class.
100*
)(
100
3
3
HouseholdsFamilySingleofNumber
ftFamilySinglebyUseWater
ftperhouseholdperUseWater = (3-4)
Table 3-11 shows the detailed price structures of City of Pullman from the year 1971
to 2006.

42
Table 3-11: Marginal and Fixed Price Rates of City of Pullman
Marginal Price
Ready to
serve
($/100 ft3
) Base Fee ($)
Year
(501-1000) ft3
(1001-2000) ft3
(2001-3000) ft3
Over 3001 ft3
1971 0.32 0.24 0.16 0.12 2.75
(0-500) ft3
(500-2000) ft3
Above 2000 ft3
1972 0.44 0.36 0.20 2
Volume charge above 500 ft3
($)
1 inch meter
size
1981 0.29 1.8
1981 0.34 5.2
1988 0.51 7.8
1991 0.55 8.46
1992 0.6 9.18
1993 0.65 9.96
1994 0.7 10.81
1995 0.71 10.98
1996 0.75 11.53
Volume charge above 500 ft3
Winter (October – May)
Summer(June-
September)
1 inch meter
size
1998 0.88 20.09
1999 0.92 1.13 20.99
2000 0.96 1.18 21.93
2000 0.96 1.18 21.93
2001 1 1.23 22.92
2002 1.05 1.29 23.95
2003
Winter Summer
(500-800) ft3
Over 800 ft3
(500-800) ft3
(801-2000) ft3
Over 2000ft3
($/100 ft3
)
1 inch meter
size
2004 1.1 1.15 1.3 1.4 1.75 24.9
2005 1.14 1.2 1.35 1.46 1.82 25.9
2006 1.19 1.24 1.41 1.51 1.89 26.93
Source City of Pullman
The marginal price of the City of Pullman is based on the volumetric water use. Up to
500 cubic feet for any kind of user class, no marginal price is to be paid but certain ready to
serve (fixed price) is to be paid whether water is used or not. The fixed charge also varies
according to the user class and size of the meter (Lamar and Weppner, 1995). The city of
Pullman has increasing block rate of marginal water price varying in the peak (summer) and

43
off-peak season (winter) and also differs according to the user classes. A one inch meter size
is taken as the representative in the calculation assuming the majority of the single family
uses this meter size. If we analyze the water use pattern of single families, there is more than
a 20 percent increase in marginal price from the year 2000 to 2006. At the same time, water
use increased 11 percent in this duration. An ordinary least square method in log linear
regression form was used to find out the relation among the variables. The expected results
are household water use positive, marginal price negative, fixed charge negative, income
positive and precipitation negative.
The monthly water extraction from the years 2000 to 2006 was used in all scenarios.
Figure 3-3 shows the annual water consumption of residential sector of City of Pullman
(Single, Duplex, Multi, Group and Mobile homes) and marginal price from the year 2000 to
2006.
710
715
720
725
730
735
740
745
750
755
760
2000 2002 2004 2006
Year
WaterConsumption(Million
Gallons)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
MarginalPrice($/100ft3)
Water
Consumption
Marginal
Price
Figure 3-3: Water Consumption and Marginal Price
Figure 3-3 shows an undulation in the water consumption. It starts approximately 715
million gallons in 2000 and reaches 750 million gallons at 2007 with an increasing trend. At

44
the same time, the marginal price of water is increasing. Figure 3-4 shows the monthly water
consumption trend of residential sector from the year 2000 to 2006. In summer time, water
consumption is relatively higher than winter period.
0.000
20.000
40.000
60.000
80.000
100.000
120.000
2000 2001 2002 2003 2004 2005 2006 2007
Year
MonthlyWaterConsumption
(MillionGallons)
Residential
Sector
Figure 3-4: Monthly Water Consumption of Residential Sector of City of Pullman
There are other specific limitations in this study. Because of a lack of exact service
connections, numbers of single family household data are used from some literature reviews.
The population, household size and median household income are generally calculated
annually and some are calculated on a decade basis. So, there is difficulty in collecting these
data in monthly basis. So these data are linearly interpolated in monthly basis. The household
level survey data is more precise and effective for calculating price elasticity. Table 3-12
shows the sample data for calculating price elasticity of water demand of single family.
Appendix B presents comprehensive data set of City of Pullman for economic analysis.

45
Table 3-12: Sample Data for Economic Analysis of Single Family, Pullman, Washington
Year Fixed Price
Marginal
Price
Median
Household
income
Precipitation
(2000)
Household
Water Use
/100 ft3
$ (1inch meter size) ($/100 ft3
)
Household
size
($ / year) (in / month)
Month Q FP MP H I P
January 6.11 21.93 0.96 2.24 21,662 1.90
February 5.67 21.93 0.96 2.24 21,696 2.66
March 6.57 21.93 0.96 2.24 21,731 2.31
April 5.81 21.93 0.96 2.24 21,765 1.21
May 7.67 21.93 0.96 2.24 21,799 2.14
June 10.92 21.93 1.18 2.24 21,833 1.19
July 16.47 21.93 1.18 2.24 21,867 0.01
August 23.14 21.93 1.18 2.24 21,902 0.04
September 17.78 21.93 1.18 2.24 21,936 1.51
October 8.15 21.93 0.96 2.24 21,970 1.65
November 7.18 21.93 0.96 2.24 22,004 1.86
December 6.05 21.93 0.96 2.24 22,038 1.44
Due to the limitation of this study, the monthly commutative time series data is used.
These types of aggregated time series data have lot of complications as if it is difficult to
understand the behavior of individual households.

46
CHAPTER IV
MODEL DEVELOPMENT SCENARIOS
4.0 Overview
A systems model of the Palouse Basin water resources was constructed using
STELLA software to evaluate water resources sustainability. The model is founded on the
data and water balance approach presented in Chapter 3, and includes a demand component
and basic economic considerations. Two versions were created: a lumped model that treats
the entire basin as a single unit designated the “Simple Model” (SM), and a “Hydrologically
Separated Model” (HSM) model that divides the basin into sub-units to account for some
spatial differences in supply and demand. Since many of the variables were uncertain,
selected parameters were allowed to vary, and uncertainty analysis was performed. This
chapter describes the conceptual modeling approach and its construction. Appendix C
presents the models as implemented in STELLA.
The Hydrological Model, Population and Demand Forecast Module, Surface Water
Utilization Module and Economic Module are described herein. The most common term
(groundwater aquifer) here indicates the stock which accumulates and depletes over time.
Basically, the Wanapum and Grande Ronde aquifers are stocks or reservoirs in the System
Dynamics Approach. The term “recharge” indicates flow which changes the magnitude of
reservoirs over time. The extraction of water from the groundwater aquifers and surface
water systems are flows.
4.1 Interactions among the Models
The forecasted population from the population model is used by demand forecast
model. Demand model uses per capita per day water use for forecasting water demand. After

47
the projection of population, demand model forecasts water demand. Consequently, water
extraction process is carried out from groundwater and surface models. The economic
module also calculates the water demand of City of Pullman. Total water demand calculated
from economic module is converted into per capita per day water use by dividing population.
Figure 4-1 shows the interactions among these models. The dashed line from economic
module Pullman to per capita per day water use shows that the economic module can be
linked to the entire system by calculating per capita per day water use. In the modeling
presented here, water demand based on economic factors is not included as part of the model.
The dashed line from the surface water module and groundwater model shows that
the linkage between these models in the structural formation but once the water reached in
the systems, there is no interaction between them. It means water is extracted from the
groundwater and surface water independently.
Population
Model
Demand
Model
Groundwater
Model
Surface Water
Module
Economic
Module Pullman
Population
Forecast
Water Demand
Forecast
Groundwater &
Recharge Estimate
Surface Water
Estimate
Water Demand Forecast
with Economics
Per Capita Per Day
Water Use
Figure 4-1: Interaction between the Models

48
4.2 Population and Demand Forecast Model
Population directly affects the demand of water, and population growth is essential
for modeling future water demand. As the groundwater basins were separated hydrologically
in different basins, the water consumption of each basin differed because of the inequality of
the population densities within the basins. This separation enables us to model the water
demand and water use within the sub-watershed. Population was forecasted by a simple
exponential growth model for each city. Exponential population growth of population
forecast is given by Equation 4-1.
rt
op ePP *= (4-1)
where, Pp is the projected final population, Po is the initial population, r is the population
growth rate and t is time. The projected final population is used in the Demand Forecast
Module for designated year. An annual water demand is computed by the population and per
capita per day water use. Figure 4-2 shows the population model used in this study.
Total Population
Growth
Population Growth Rate
Figure 4-2: Population Model
The forecasted population from Equation 4-1 is 139,168 people for the coming
hundred years. Equations 4-2, 4-3, 4-4 and 4-5 show stocks, inflows and converters in
equation mode of STELLA for forecasting population. Equation 4-2 is similar to Equation 4-

49
1. It is intended here to show how the System Dynamics Approach works from this simple
model.
STOCKS:
dtGrowthdttPopulationtPopulation *)()()( +−= (4-2)
51197=PopulationINT (4-3)
INFLOWS:
RateGrowthPopulationPopulationGrowth *= (4-4)
CONVERTER:
01.0=RateGrowthPopulation (4-5)
where, dt is the time increment in the calculation and t is time. The forecasted population
from Equation 4-2 is 139,073 people at the year 2100.
4.3 Hydrological Model
The hydrologic section is divided into surface water hydrology and groundwater
hydrology. Surface water hydrology is described by mean annual precipitation, surface
runoff and evapotranspiration; recharge is computed by water balance assuming that the
average soil moisture storage change in the unsaturated zone is zero. The water balance
estimate of recharge is applied to shallow groundwater where shallow groundwater is known
to exist, and recharge to the deeper aquifer. The volume of groundwater in the aquifers is
computed using estimates of the aquifer areas and storativities made by geologists working in
the basin. Groundwater regions are assumed as non-leaking reservoirs. It is assumed that
recharge only occurs vertically and no lateral flow occurs during this process. Surface water
watersheds are delineated solely from USGS gauging station locations in order to perform
mass balance computations. Groundwater regions are determined from geologic formation of

50
aquifers and information availability. Due to the geographic variation between the surface
and groundwater regions, all the water that is assumed to percolate from the surface does not
reach the designated groundwater regions. In addition, the groundwater regions receive
different rates of recharged water. This is a basic assumption of the conceptual model used in
this study: distributed recharge to groundwater aquifers only occurs where the relevant basalt
formations exist. This conceptualization does not account for potential concentrated recharge
zones, for example, along stream channels.
Figure 4-3 shows the groundwater-surface water overlay, combining Figures 1-1
(surface water watersheds) and 1-3 (groundwater regions) from Chapter 1.
Figure 4-3: Groundwater- Surface Water Overlay
(Source: Palouse Basin Community Information System, 2007)
The area of surface water watershed is approximately 2,044 square kilometers and the
underlying groundwater area is 769 square kilometers. The majority of the sub-watershed
delineated by USGS gauging station 1334500, Palouse River near Potlatch, ID, was outside
the designated basalt groundwater regions. Also certain portions of all surface water sub-

51
watersheds lie outside groundwater regions. Some portion of the Colfax groundwater region
is above the confluence point of the South Fork and the North Fork Rivers, so this portion of
the groundwater region and the Uniontown groundwater region is outside the groundwater-
surface water overlay. That portion of recharged water which lies outside the groundwater
regions are not incorporated into the groundwater system. This does not affect the surface
water balance but does influence the groundwater computations. If future investigations
clarify the spatial distribution of recharge, or locations of more concentrated recharge, the
model can be modified accordingly.
Within the present infrastructure conditions, the average potential groundwater
drawdown from the pumping level to the pump intake level is 26 meters and 34 meters of the
Moscow Wanapum and Grande Ronde respectively (Table 3-3). The maximum potential
groundwater drawdown from the current pumping level to the bottom of the wells of the
Moscow and Pullman are shown at Table 3-3. The average value of the maximum potential
groundwater drawdown of the Moscow Wanapum is 74 meters, Moscow Grande Ronde is
271 meters and Pullman Grande Ronde is 161 meters (Table 3-3) up to the bottom of wells.
These potential groundwater drawdown values are used throughout the simulation for
calculating maximum drawdown in future extension scenarios. The maximum potential
groundwater drawdown of Colfax, Viola and Palouse is taken as the average saturated
thickness. At present, Moscow Wanapum is only potential for producing groundwater. So,
the total volume of the groundwater in the entire Wanapum is taken as the groundwater
volume of Moscow Wanapum. The remaining groundwater regions are assumed to be
unproductive for the groundwater. But water balances still exist in those areas in the Simple
Model and it is assumed that the recharge water either will be stored in the Wanapum system

WATER RESOURCE SUSTAINABILITY OF THE PALOUSE REGION: A SYSTEMS APPROACH

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