The document discusses sustainability of groundwater use in the San Pedro River Basin of Arizona. It notes declining streamflows in the river, dropping to zero in summer 2005, due to increasing groundwater pumping. A partnership of agencies is working to identify solutions to ensure reasonable water supplies for both the river and local communities. The USGS is conducting studies to better understand the basin's hydrogeology and riparian water needs to inform setting a sustainable groundwater yield under the Congressional mandate. Adaptive management using monitoring data will help assess progress toward the sustainability goal over time.

1. U.S. Department of the Interior
U.S. Geological Survey
Sustainability of Ground-Water
Use in the San Pedro River
Basin, Cochise County, Arizona
James Leenhouts, Ph.D.
IAEA/GEF IW Learn/USGS Aquifer Exchange
April 19, 2007

2. The Upper San Pedro Basin
 San Pedro River
flows north from
near Cananea,
Mexico to Gila
River
 4,480 km2
area
above Tombstone
gage
 1,810 km2
in
Mexico
 2,670 km2
in U.S.
Fort
Huachuca

3. The Problem: Competing Assets
 The San Pedro’s riparian system
(SPRNCA)
 Federally protected in 1988
 One of shrinking number of free-
flowing perennial rivers in the
Southwest
 The human community
 National asset: Fort Huachuca
 Growing population
 Great climate, beautiful environs

4. Streamflow at Charleston
Total uses
0
10
20
30
40
50
60
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
YEAR
GROUND-WATER
WITHDRAWALS,inCUBIC
HECTOMETERS
0
10000
20000
30000
40000
GROUND-WATER
WITHDRAWALS,
inACRE-FEET
Pumping
Streamflow
Fort
Huachuca

5. Zero flow at Charleston, Summer 2005
June-July 2005 Charleston Streamflow
0
2
4
6
8
10
6/1/05 6/16/05 7/1/05 7/16/05 7/31/05

8. Investigations
 Geohydrologic studies
 Improve the conceptual model
 Detailed investigation of physical system
 Synthesis in ground-water model
 Riparian water needs studies
 Multidisciplinary study
 Related hydrologic variables to riparian condition
 Quantified riparian ET

9. Geohydrologic Studies
 Water levels
 Streamflow
 Aquifer storage change - microgravity
 Geophysical exploration
 Unsaturated zone flow
 Stream temperature monitoring
Lacoste and Romberg Model
D
Relative-gravity meter

10. Investigations
Network

11. WETLANDS
STREAM
BEDROCK
ETET
RECHARGE
RECHARGE
CURRENT CONCEPTUALCURRENT CONCEPTUAL
GROUND-WATER FLOWGROUND-WATER FLOW
SYSTEMSYSTEM
Spring
limestone
EPHEMERAL
STREAM
RECHARGE
EPHEMERAL
STREAM
RECHARGE
EAST WEST

12. WETLANDS
STREAM
BEDROCK
SCHEMATICSCHEMATIC
REPRESENTATION OFREPRESENTATION OF
GROUND-WATER FLOWGROUND-WATER FLOW
MODELMODEL
BEDROCK
LAYER 3
RECHARGE
RECHARGE
ETET
EAST WEST
EPHEMERAL
STREAM
RECHARGE
EPHEMERAL
STREAM
RECHARGE
RECHARGE
RECHARGE
LAYER 5
LAYER 4
LAYER 2
LAYER 1

13. Riparian Water Needs Investigation
 Three components
 Hydrology
 Ecology
 Evapotranspiration

14. Riparian
Condition
Class
 Relates
hydrology to
ecology
 Provides
science to
inform policy

15. The Mandate: Sustainable Yield
 Stipulated by Congress
 Not safe yield --> pumping = recharge
 Sustainable Ground-Water Yield
 “…the development and use of ground water in a
manner that can be maintained for an indefinite
time without causing unacceptable environmental,
economic, or social consequences.”

16. The Players
 Upper San Pedro Partnership
 21 local, state, federal, and non-
governmental agencies
 Goal is to identify and implement
solutions to assure reasonable
water supply for the river and the
people
 AZ congressional delegation
 Other groups

17. Reservoir
Analogy
No Pumping
Safe Yield
Sustainable
Yield

18. Initial Criteria for Sustainability
 Unacceptable consequences:
 The riparian system ceases to function
 Unavailability of water causes Fort Huachuca to
close

19. Sustainable yield
 How much water:
 Do the people need?
 Does the riparian system
need?
 Temporal effects
 Spatial effects
 Climatic effects

20. Ground-Water Budget

21. Sustainable yield – initial goal
An Aquifer-Storage Approach

22. Sustainability – defined spatially
 Define indicators and thresholds
 Indicators – variables that inform status
 Thresholds – markers beyond which sustainability
fails
Environment Socioeconomic
Indicator Threshold Indicator Threshold
Ground-water levels –
regional aquifer ? ? ?
Streamflow
? ? ?
Spring discharge
? ? ?
Ground-water levels –
alluvial aquifer
Defined by water-
needs study ? ?

23. Assessing
Progress =
Monitoring
 Water budget aspects
 Tabulation of pumping
 Continued refinement of
inflow and outflow values
 System-response aspects
 Water levels
 Microgravity
 Spring and stream
discharge
 Vertical gradients

24. Sustainable Yield – Adaptive
Management
 Iterative interaction
 Management Action
 Monitoring
 Analysis

25. Science
Informing Policy
 Spatial definition
of ground-water
management
 “Capture map”

26. Semiarid: Only half of the residents drive camels
Questions?

27. Reaching the Goal
 Broad categories of water management
measures:
 Conservation
 Growing population
 Recharge
 Needs source of water
 Importation
 Potential legal issues

28. Perennial
Intermittent
Stream gage

29. Who, What, Where, When, How?
June-July 2005 Charleston Streamflow
0
2
4
6
8
10
6/1/05 6/16/05 7/1/05 7/16/05 7/31/05

30. Interaction of Multiple Factors
Summer (June) 7-Day Low Flow at Charleston, 1936-2005
0
1
2
3
4
5
6
7
8
9
10
1930 1940 1950 1960 1970 1980 1990 2000
Streamflow,cubic-feet-per-sec.
June 7-day low flow
5-year average
2005 streamflow data not yet verified.

31. Annual Section 321 Reports
 See the 2004 Section 321 report at:
http://water.usgs.gov/Section321.2004_050705.pdf

32.  Sustainability:
 “…the development and use of ground water in a
manner that can be maintained for an indefinite
time without causing unacceptable environmental,
economic, or social consequences.”

33. Outline
 Introduction to basin – talk about SPRNCA – usual superlatives, Fort, Cities
 The issues – declining streamflows, zero flow.
 Discussion of the players
 Capture
 Description of work done – model, water needs.
 Sustainable yield goal – Section 321
 Status of water budget – include reservoir analogy to sustainable yield
 Science to policy section
 Section 321 reports
 Capture maps
 Level change maps
 Gravity maps