Ground-Water Hydrology of the Upper Klamath Basin, Oregon and ...

Acknowledgments 65
Hydraulic head in the upper Klamath Basin fluctuates
primarily in response to climate, pumping, canal and irrigation
operations, and lake stage. Basinwide, climate exerts the
largest influence on water levels. Water levels in upland areas
have declined more than 12 feet between 2000 and 2006 in
response to drought conditions; however, they are expected
to rise again when wet conditions return. Because climatedriven
fluctuations affect the entire basin, they have the largest
influence on the hydrologic system and are responsible for the
large variations in ground-water discharge to streams.
Water level fluctuations in response to pumping are most
commonly seasonal, with the water level declining during
the irrigation season and recovering more or less fully by
the following spring. Prior to 2001, year-to-year water-level
declines due to pumping were rare in the upper Klamath
Basin. The large localized increase in pumping that began
in 2001 has resulted in year-to-year declines in the Klamath
Valley and Tule Lake subbasin. The total decline between
2001 and 2004 exceeds 15 feet in parts of these areas and is
larger than can be attributed to drought alone. These year-toyear
declines have been accompanied by amplified seasonal
declines. How long it will take water levels to recover fully
after wet climate conditions return and pumping stress is
reduced is not known. Data clearly show that pumping stresses
can cause measurable head responses over broad parts of the
ground-water system.
Irrigation and canal operation also affect water levels,
particularly in shallow aquifers. Water levels in these aquifers
rise at the beginning of the irrigation season and decline
during the off-season. The magnitude of this fluctuation is
generally 5 to 10 feet in the main part of the Klamath Project.
Water levels in wells near Upper Klamath Lake fluctuate in
concert with lake stage.
This study was intended to develop an understanding of
the regional ground-water flow system in the upper Klamath
Basin to help resource managers and basin residents develop
a strategy for managing ground water. Developing a groundwater
management strategy for the upper Klamath Basin will
require consideration of general characteristics of groundwater
flow and characteristics unique to the upper Klamath
Basin. Generally, increases in the rate of pumping from
a ground-water system will eventually be offset by either
increased rates of recharge or (more likely) diminished rates
of discharge. Mechanisms whereby ground-water recharge
is increased by pumping are rare. In some circumstances, the
lowering of hydraulic head caused by pumping could cause
increased leakage from streams to the ground-water system.
Conditions where this could occur in the upper Klamath Basin
are rare. Pumping ground water near basin boundaries can
cause the boundaries to shift, effectively capturing recharge
from adjacent basins. However, only a fraction of the pumpage
would be made up by flow from adjacent basins given likely
pumping locations. Diminishment of discharge is the more
likely consequence of ground-water extraction. Most of the
decrease would be in ground-water discharge to streams,
although reductions in discharge to phreatophytes (riparian or
wetland vegetation with roots that extend to the water table)
and in flows of ground water moving out of the basin in the
subsurface could occur as well.
The timing and distribution of the effects of groundwater
use are dictated to a large degree by the location of
pumping. Pumping very near to discharge areas, such as
springs, can diminish the flow of the springs relatively quickly.
There have been several instances (with varying amounts of
documentation) where ground-water pumping has affected
spring discharge in the upper Klamath Basin. Springs affected
by pumping in the past include those in Bonanza, elsewhere
in the Lost River subbasin, and near Whisky Creek in the
Sprague River subbasin.
Ground water is a major component of streamflow in
the upper Klamath Basin, and, consequently, ground-water
development has the potential to affect streamflow. Because
the rate, spatial distribution, and variability of ground-water
discharge in the upper Klamath Basin is now well understood,
ground-water management strategies can be developed that
minimize the effects of ground-water use.
Recently, a considerable effort has been made by various
agencies, including the U.S. Geological Survey, the Oregon
Water Resources Department, the California Department of
Water Resources, and the Bureau of Reclamation, to monitor
ground-water levels and ground-water discharge in the
upper Klamath Basin. This information has been valuable in
developing the present understanding of the regional groundwater
system and its response to natural and human-caused
stresses. Continued data collection will be important in the
future to quantify the response of the ground-water system to
stresses.
Acknowledgments
The authors gratefully acknowledge the support of the
residents of the upper Klamath Basin, particularly the many
hundreds of individuals who allowed access to property and
wells for water-level measurements and monitoring over the
course of several years. Our understanding of the groundwater
hydrology of the upper Klamath Basin benefited
tremendously from many hours of discussions with land
owners and scientists working in the basin, who freely shared
observations, insights, and valuable data. Particular thanks go
to Noel Eaves and Bill Ehorn of the California Department of
Water Resources; Jon Hicks, John Rasmussen, and Tom Perry
of the Bureau of Reclamation; Jerry Grondin and Ned Gates
of the Oregon Water Resources Department; Tim Mayer of
the U.S. Fish and Wildlife Service; Mike Stansbury of Water
and Energy Services (WESCORP); Steve Luxton of W&H
Pacific; Toni Boyd and John Lund of the Oregon Institute of
Technology Geo-Heat Center; and the staffs of the Klamath
National Wildlife Refuges Complex and Lava Beds National
Monument. Our understanding of the geology of the region