1. RAM RAO
CIVE 544
Water Resources Planning and Management

2.  Area of Study, Central Valley
(San Joaquin Valley) of
California: 26,000 square
kilometers
 Land Use, Primarily
Agricultural
 Economic Value (>$20
Billion [Faunt, 2009])
 Water Supply
 Until the 1950s and
1970s – Groundwater
 Since the 1950s and
1970s – Surface Water
Plus Groundwater

3.  Historical Perspective Through the 1970s
 Groundwater Pumping and Mechanics
of Subsidence
 Current Perspective
 Summary of Studies
 Subsidence Along the Aqueduct and the DMC
 Correlation with Groundwater Pumping
 Options for Management of
Subsidence

4. Effect of Pumping is Significant
Subsidence of Land; Location
of Maximum Subsidence in U.S.
Near Mendota, California
[Researcher, Joseph Poland]
 Historically and
Until the
Construction of the
Canals:
Groundwater is
Major Supply
 Significant
Subsidence of Land
Noted – up to 9 m
(Ireland, 1986)
 Since the 1950s –
Surface Water
Supply Reduces
Dependence on
Groundwater

5.  Water Source:
Coast Ranges to the West
Sierra Nevada to the North and the East
Tehachapi Mountains to the South
 Key Projects (Supplements Groundwater Use
in the Central Valley)
 CVP – BOR, Late 1950s
 SWP – California DWR, Late 1960s
 DMC – Built by BOR;
Operated by SLDMWA
 California Aqueduct – Built by BOR
and California DWR; Operated by DWR
 Friant Kern Canal – Built by BOR;
Operated by Friant Water Authority
CVP – Central Valley Project;
SWP – State Water Project

6.  Lowering Water Level
by Groundwater
Pumping:
 Total Stress
Remains Same
 Reduces Pore
Water Pressure
 Increases Effective
Stress
 Causes
Compaction and
Settlement

7.  Prior to Development:
 Recharge from Mountains
Toward Valley Trough
and Upward to Rivers
/Sloughs [No Change in
Groundwater Storage]
 After Development:
 Recharge from Mountains
Pumping and Recharge
from Irrigation Increases
Downward Gradients and
Flow Toward the Valley
Trough. Decline in Water
Level Below Confining Unit
Causing Lag in Subsidence

8.  Groundwater Pumping Prior to
Surface Water Diversion (DMC
and California Aqueduct
Operation)
>8 Million Acre Feet/Year
 On an Annual Basis,
Approximately 25% of U.S.
Pumping in the San
Joaquin Valley

9.  From 1970s
Surface Water Surpasses
Groundwater
 Drought Conditions
Reverses Trends
Causes Reversion Back to
High Groundwater
Pumping Conditions
(1977)

10.  USGS and California DWR
Studies, 1956 to 1986
 Poland, 1995
 DWR and Other Water
Agency Measurements
 USGS, BOR, and SLDMWA,
2009 (Results Presented
Herein)
 GPS Measurements
 Extensometer Data
 Interferometric
Synthetic Aperture
Radar (InSAR):
2009 Study Area Map

11.  Mapped Through the
1960s During Period
Of High Groundwater
Pumping
 Maximum Subsidence
Noted Near:
 Mendota (~9 m)
 North of Kettleman
City

12. Insar Data
Joint Effort Between
USGS, USDOI, and Water
Agencies
 Maximum Subsidence
Data Now to the North
Of Mendota Near El
Nido
 >500 mm over Two
Year Period Near El
Nido (Drought Period
2008-2010)

13. Measured During
Drought Period
 Northern Segment of the
DMC and the California
Aqueduct
 Little to No
Subsidence
Observed
 Locations of Uplift
Noted Instead

14.  Southern Segment of the
DMC
 Higher than the
Northern Segment
Lower than El Nido
Area

15. Measured During
Drought Period
 Central Segment of the
DMC
 Highest Noted
El Nido Area
 540 mm Over
Two Year Period

16. Northern Segment
Of the DMC and the
California Aqueduct
 Seasonal
Fluctuations Noted
in Wells
 Less Significant
Periodic Decline In
Drought Period
After 2008
 Correlates with a
General Absence of
Subsidence – InSar
Data

17. Central Segment of DMC
Near El Nido Area
And Southern Segment
Near Mendota
 Seasonal Fluctuations
Noted in Wells
 More Significant
Periodic Decline
During Drought
Period Following 2008
 Correlates with High
Subsidence – InSar
Data (540 mm Max)
 Correlation Good Near
Mendota (P-304)

18.  Land Subsidence
And Groundwater
Pumping
Good Correlation:
 P304 Area Near
Mendota,
California

19.  Effects on Operation
 Downstream Segments of Canal
Could become Higher than the Upstream
Segments
 Transfer of Water is Primarily by Gravity;
Higher Downstream Segments would
Hinder Operation
 DWR Found Large Swathes Impacted
~1.25 feet lower in Fresno, Kern,
and King Counties – Coinciding with the
Central and Southern Segments of the
DMC

20.  Longer Term Effects
 Liner Damage
 Liner Settlement
 Liner Buckling, Spalling
 Other Features may Become
Unusable such as Bridge
Crossings
 Areas More Prone to Flooding,
Levees/Embankments Modifications
Potential Effect on Land Use
Economic Impacts Significant:
 O&M Impacts to Broader Economy
 Asset Restoration Costs

21.  Managed Aquifer
Recharge Areas
 State and the DOI to
fund local water agencies
to issue ordinances that
promote conservation and
reduce pumping
 More “holistic” approach
toward issuance of well
extraction and permitting
 More relaxed in-stream
regulations to permit use of
surface water during months of
high demands