[env-trinity] USGS: Effects of groundwater pumping on agricultural drains in the Tule Lake subbasin, Oregon and California

[Sari Sommarstrom]

 <http://pubs.usgs.gov/sir/2015/5087/sir20155087.pdf> thumbnail

Effects of groundwater pumping on agricultural drains in the Tule Lake
subbasin, Oregon and California

Scientific Investigations Report 2015-5087

Prepared in cooperation with the Bureau of Reclamation and the U.S. Fish and
Wildlife Service

By:

Esther M. Pischel and Marshall W. Gannett 

.         Document:  <http://pubs.usgs.gov/sir/2015/5087/sir20155087.pdf>
Report (4.3 MB pdf) 

.         Download citation as:
<http://pubs.er.usgs.gov/publication/sir20155087?mimetype=ris> RIS

First posted July 24, 2015

For additional information, contact:

 <mailto:dc_or at usgs.gov> Director, Oregon Water Science Center
U.S. Geological Survey
2130 SW 5th Avenue
Portland, Oregon 97201
 <http://or.water.usgs.gov/> http://or.water.usgs.gov

Abstract

Since 2001, irrigators in the upper Klamath Basin have increasingly turned
to groundwater to compensate for reductions in surface-water allocation
caused by shifts from irrigation use to instream flows for Endangered
Species Act listed fishes. The largest increase in groundwater pumping has
been in and around the Bureau of Reclamation's Klamath Irrigation Project,
which includes the Tule Lake subbasin in the southern part of the upper
Klamath Basin. Agricultural drains on the Klamath Project are an important
source of water for downstream irrigators and for the Tule Lake and Lower
Klamath Lake National Wildlife Refuges. U.S. Geological Survey regional
groundwater-flow model simulations and records of irrigation-return flow
pumped from the Tule Lake subbasin into the adjacent Lower Klamath Lake
subbasin have indicated that water-level declines from pumping may be
causing decreased flow of shallow groundwater to agricultural drains. 

To better define the effect of increased pumping on drain flow and on the
water balance of the groundwater system, the annual water volume pumped from
drains in three subareas of the Tule Lake subbasin was estimated and a
fine-grid, local groundwater model of the Tule Lake subbasin was
constructed. Results of the agricultural-drain flow analysis indicate that
groundwater discharge to drains has decreased such that flows in 2012 were
approximately 32,400 acre-ft less than the 1997-2000 average flow. This
decrease was concentrated in the northern and southeastern parts of the
subbasin, which corresponds with the areas of greatest groundwater pumping.
Model simulation results of the Tule Lake subbasin groundwater model
indicate that increased supplemental pumping is the dominant stress to the
groundwater system in the subbasin. Simulated supplemental pumping and
decreased recharge from irrigation between 2000 and 2010 totaled 323,573
acre-ft, 234,800 acre-ft (73 percent) of which was from supplemental
pumping. The response of the groundwater system to this change in stress
included about 180,500 acre-ft (56 percent) of decreased groundwater
discharge to drains and a 126,000 acre-ft (39 percent) reduction in aquifer
storage. The remaining 5 percent came from reduced groundwater flow to other
model boundaries, including the Lost River, the Tule Lake sumps, and
interbasin flow.

Suggested Citation

Pischel, E.M., and Gannett, M.W., 2015, Effects of groundwater pumping on
agricultural drains in the Tule Lake subbasin, Oregon and California: U.S.
Geological Survey Scientific Investigations Report 2015-5087, 44 p.,
http://dx.doi.org/10.3133/sir20155087.

 

 

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