Upper Klamath Basin Regional Groundwater Studies
Since the late 1990s the U.S Geological Survey has been working to characterize the regional groundwater hydrology of the Klamath Basin above Iron Gate Dam (referred to here as the upper Klamath Basin) by collecting data to help understand the state of the groundwater system and its response to external stresses, and to develop computer models to provide insights useful for water management. These efforts build on earlier USGS studies in the basin going back to the 1950s. Most of these studies have been conducted in cooperation with the Oregon Water Resources Department, the Bureau of Reclamation, and most recently the Klamath Water and Power Agency. Following this section are short discussions on the major elements of recent work, including overviews of Groundwater Hydrology, Groundwater Model Development, Groundwater Management Modeling, and Present Activities.
This work has resulted in several scientific reports and papers that describe the regional groundwater hydrology, groundwater simulation and management model development, and the application of the groundwater management modeling to inform groundwater management in the area of the Klamath Reclamation Project. Links to these reports can be found in the Publications section below.
Overview of the Groundwater Hydrology of the Upper Klamath Basin
Snow at Crater Lake in the Cascade Range, a principal groundwater recharge area. Photo by Marshall Gannett.
The upper Klamath Basin has a substantial regional groundwater flow system. The volcanic rocks that underlie the region are generally permeable and compose a system of variously interconnected aquifers. Interbedded with the volcanic rocks are sedimentary rocks primarily composed of fine-grained lake sediments and basin-filling deposits. These sedimentary deposits have generally low permeability, are not good aquifers, and probably reduce groundwater movement in some areas. The regional groundwater system is underlain and bounded on the east and west by older volcanic and sedimentary rocks that have generally low permeability.
Groundwater flows from recharge areas in the Cascade Range and upland areas in the basin interior and eastern margins toward stream valleys and interior subbasins. Ground water discharges to streams throughout the basin, and most streams have some component of ground water (baseflow). Some streams, however, are predominantly groundwater fed and have relatively constant flows throughout the year. Large amounts of ground water discharge in the Wood River subbasin, the lower Williamson River area, and along the margin of the Cascade Range. Much of the inflow to Upper Klamath Lake can be attributed to groundwater discharge to streams and major spring complexes within a dozen or so miles from the lake. There are also groundwater discharge areas in the eastern parts of the basin, for example in the upper Williamson and Sprague River subbasins and in the Lost River subbasin near Bonanza, OR.
Headwaters of the Wood River. Photo by Brian Wagner.
Irrigated agriculture is an integral part of the economy of the upper Klamath Basin. Although estimates vary somewhat, roughly 500,000 acres are irrigated in the upper Klamath Basin, about 190,000 acres of which are part of the Bureau of Reclamation Klamath Project. Most of this land is irrigated with surface water. Ground water has been used for many decades to irrigate areas where surface water is not available, for example outside of irrigation districts and stream valleys. Ground water has also been used as a supplemental source of water in areas where surface water supplies are limited and during droughts. Ground water use for irrigation has increased in recent years due to drought and shifts in surface-water allocation from irrigation to instream uses. The shifts in surface-water allocation have resulted from efforts to improve habitat for fish listed under the Federal Endangered Species Act.
The groundwater system in the upper Klamath Basin responds to external stresses such as climate cycles, pumping, lake stage variations, and canal operation. This response is manifest as fluctuations in hydraulic head (as represented by fluctuations in the water-table surface) and variations in groundwater discharge to springs. Basinwide, decadal-scale climate cycles are the largest factor controlling head and discharge fluctuations. Climate-driven water-table fluctuations of more than 12 feet have been observed near the CascadeRange, and decadal-scale fluctuations of 5 feet are common throughout the basin. Groundwater discharge to springs and streams varies basinwide in response to decadal-scale climate cycles. The response of the groundwater system to pumping is generally largest in areas where pumping occurs. Annual drawdown and recovery cycles of 1 to 10 feet are common in pumping areas.
Since 2001, groundwater use in the upper Klamath Basin has increased. Much of this increase has occurred in the area in and around the Bureau of Reclamation Klamath Project. This focused increase in pumping has resulted in groundwater level declines. Keeping the declines within acceptable limits while providing adequate water for irrigation is a challenge for regulatory agencies and water users. Models can provide useful insights for managing groundwater.
Overview of the Regional Groundwater Model
Observed and simulated groundwater discharge to the upper Williamson River, Oregon.
The potential effects of increased groundwater pumping on groundwater levels and discharge to springs and streams has caused concern among groundwater users, wildlife and Tribal interests, and State and Federal resource managers. To provide information on the potential impacts of increased groundwater development and to aid in the development of a groundwater management strategy, the U.S. Geological Survey has developed a groundwater model that can simulate the response of the hydrologic system to these new stresses.
The groundwater model was developed using the U.S. Geological Survey MODFLOW finite-difference modeling code and calibrated conditions from 1989 through 2004 with quarterly stress periods. Groundwater recharge and agricultural and municipal pumping are specified for each stress period. All major streams and most major tributaries for which a substantial part of the flow comes from groundwater discharge are included in the model. Groundwater discharge to agricultural drains, evapotranspiration from aquifers in areas of shallow groundwater, and groundwater flow to and from adjacent basins also are simulated in key areas. The model has the capability to calculate the effects of pumping and other external stresses on groundwater levels, discharge to streams, and other boundaries, such as discharge to drains.
Historical data indicate that the groundwater system in the upper Klamath Basin fluctuates in response to decadal climate cycles, with groundwater levels and spring flows rising and declining in response to wet and dry periods. Data also show that groundwater levels fluctuate seasonally and interannually in response to groundwater pumping. The calibrated model is able to simulate observed decadal-scale climate-driven fluctuations in the groundwater system as well as observed shorter-term pumping-related fluctuations.
Model simulations show that the timing and location of the effects of groundwater pumping vary markedly depending on pumping location. Pumping from wells close to groundwater discharge features, such as springs, drains, and certain streams, can affect those features within weeks or months of the onset of pumping, and the impacts can be essentially fully manifested in several years. Simulations indicate that seasonal variations in pumping rates are buffered by the groundwater system, and peak impacts are closer to mean annual pumping rates than to instantaneous rates. Thus, pumping effects are, to a large degree, spread out over the entire year. When pumping locations are distant from discharge features, the effects take many years or decades to fully impact those features, and much of the pumped water comes from groundwater storage over a broad geographic area even after two decades. Moreover, because the effects are spread out over a broad area, the impacts to individual features are much smaller than in the case of nearby pumping. Simulations show that the discharge features most affected by pumping in the area of the Bureau of Reclamation's Klamath Irrigation Project are agricultural drains, and impacts to other surface-water features are small in comparison.
Overview of Groundwater Management Modeling Efforts
A well pumping supplemental irrigation water in the upper Klamath Basin. Photo by Marshall Gannett.
A groundwater management model was developed that uses techniques of constrained optimization along with the groundwater flow model to identify optimal strategies to meet water-user needs while not violating defined constraints on impacts to groundwater levels and streamflows. The overall goal of the groundwater-management modeling effort was to determine the patterns and rates of groundwater pumping that, to the extent possible, meet the supplemental groundwater demands of the Klamath Reclamation Project. To ensure that groundwater development does not adversely affect groundwater and surface-water resources, the groundwater-management model includes constraints to (1) limit the effects of groundwater withdrawal on groundwater discharge to streams and lakes that support critical habitat for fish listed under the Endangered Species Act, (2) ensure that drawdowns do not exceed limits allowed by Oregon water law, and (3) ensure that groundwater withdrawal does not adversely affect agricultural drain flows that supply a substantial portion of water for irrigators and wildlife refuges in downslope areas of the Project.
Groundwater-management scenarios were evaluated for the period 1970-2004; supplemental groundwater demand by the Project was estimated as the part of irrigation demand that would not have been satisfied by the surface-water diversion allowed under the Klamath Basin Restoration Agreement. Over the 35-year management period, 22 years have supplemental groundwater demand, which ranges from a few thousand acre-feet (acre-ft) to about 100,000 acre-ft in the driest years.
The results of the groundwater-management model indicate that supplemental groundwater pumping by the Project can be managed to avoid adverse effects to groundwater discharge that supports critical aquatic habitat. The existing configuration of wells in the Project would be able to meet groundwater-pumping goals in 14 of the 22 years with supplemental groundwater demand; however, substantial irrigation shortages can be expected during drought periods when the demand for supplemental groundwater is highest. The maximum irrigation-season withdrawal calculated by the groundwater-management model is about 60,000 acre-ft, the average withdrawal in drought years is about 54,000 acre-ft, and the amount of unmet groundwater demand reaches a maximum of about 45,000 acre-ft. A comparison of optimized groundwater withdrawals by geographic region shows that the highest annual withdrawals are associated with wells in the Tule Lake and Klamath Valley regions of the Project. The patterns of groundwater withdrawal also show that some of the available pumping capacity is unused due to the restrictions imposed by drawdown constraints.
Hydrograph showing water-level declines in the northern Tule Lake subbasin. Data from the Oregon Water Resources Department. Data from all monitored wells in the upper Klamath Basin can be found on the Upper Klamath Groundwater Monitoring page.
Planned interpretive groundwater studies are largely completed, and present efforts are focused on monitoring groundwater levels in the basin to provide information on the state of the aquifer system and its response to climate and pumping stresses. Most recently, the USGS has been working with the Klamath Water and Power Authority, the Oregon Water Resources Department, and the California Department of Water Resources to coordinate groundwater monitoring activities and to provide a single point of access to water-level data and interpretations for water users and the public at large. For more information refer to the Collaborative Groundwater Monitoring page.
Streamflow is monitored in the upper Klamath Basin by both USGS and the Oregon Water Resources Department:
The U.S. Geological Survey conducts a broad range of studies in the Klamath Basin. A listing of studies and related links can be found on the USGS Oregon Water Science Center Klamath Basin Studies page.
Cooperative studies conducted by the U.S. Geological Survey have resulted in several reports dealing with groundwater and related topics. These studies all rely heavily on multi-agency groundwater monitoring efforts. Click on the following links to read abstracts and to download the reports.
Groundwater Hydrology of the Upper Klamath Basin, Oregon and California - This report describes the geologic framework of regional groundwater flow in the basin, regional groundwater hydrology, the hydrologic budget, and groundwater/surface-water interaction. It also describes the response of the groundwater system to external stresses such as climate and pumping.
Groundwater Simulation and Management Models for the Upper Klamath Basin, Oregon and California - This report describes the development, calibration, and application of a regional groundwater flow model for the upper Klamath Basin and a coupled management model. The flow model is based primarily on the conceptual framework described in the above report. The report also describes a groundwater management model that can identify optimal groundwater management strategies given certain defined objectives, constraints, and decision variables. The report included example applications.
Evaluation of Alternative Groundwater-Management Strategies for the Bureau of Reclamation Klamath Project, Oregon and California - This report describes the application of the coupled groundwater simulation and management models to evaluate strategies for using groundwater to supplement surface-water supplies on the Klamath Reclamation Project while avoiding unacceptable groundwater-level declines or impacts to streams. Several alternatives are evaluated in the context of varying climate.
Evapotranspiration from marsh and open-water sites at Upper Klamath Lake, Oregon, 2008 – 2010 - Evapotranspiration (the movement of water from the land surface to the atmosphere though evaporation and plant transpiration) is one of the largest components of the hydrologic budget, and key to understanding groundwater and surface-water hydrology. This report describes measurements of evapotranspiration from large wetlands north of Upper Klamath Lake and open-water evaporation from the lake itself using eddy covariance and energy-balance methods.
An evaluation and review of water-use estimates and flow data for the Lower Klamath and Tule Lake National Wildlife Refuges, Oregon and California - This report describes the hydrologic budgets of two large wildlife refuges south of upper Klamath Lake. It includes estimates of major inflows such as precipitation, streams, canals, irrigation drains, as well as outflows to evapotranspiration, pumps, canals, and drains. Flow to and from the groundwater system is also estimated.
Isotopic characterization of three groundwater recharge sources and inferences for selected aquifers in the upper Klamath Basin of Oregon and California, USA - This paper uses stable isotopes and other water-chemistry data to identify sources of recharge to selected aquifers in the upper Klamath Basin. Three sources of recharge considered are the Cascade Range, uplands east of the Cascade Range, and the irrigation.