Upper Klamath Basin Groundwater Studies

The upper Klamath Basin has a large regional groundwater-flow system that provides much of the water to major streams and lakes. The underlying volcanic rocks have abundant interconnected pore spaces, allowing water to flow underground at relatively high rates. The volcanic rocks are interlaid with sedimentary rocks, some composed of fine-grained lake sediments. The sedimentary layers tend to restrict water flow and are generally poor productivity aquifers.  Groundwater moves through the interconnected layers of rock and eventually emerges into streams, lakes, and springs.  Large amounts of groundwater supply the Wood River Subbasin, and the lower Williamson River, and provide some direct inflow to upper Klamath Lake. The groundwater supply to upper Klamath Lake somewhat buffers the lake water levels during dry seasons.  

In the previous century, high demand for water in the Klamath Basin and frequent drought conditions increased the strain on groundwater resources. In 2001, limits on surface-water use for irrigation began. Limits on surface water are meant to keep enough water in streams and rivers for critically endangered fish habitat but the limits consequently can reduce the amount of water available for irrigation. As a result, groundwater pumping from wells for irrigation increased substantially since 2001. USGS is helping define and summarize the effects of increased pumping. USGS scientists monitor groundwater levels using various instruments deployed in wells throughout the basin. The water-level data inform resource-management decisions on the relationship between pumping and groundwater-level change.   

Modeling insights: 

Groundwater models indicate that pumping from wells close to groundwater discharge features, such as springs, drains, and certain streams, can decrease water levels and groundwater discharge within weeks or months of the onset of pumping. When pumping locations are distant from discharge features, it can take many years or decades for the effects to be felt.  

In the southern part of the Upper Klamath Basin, the Tule Lake subbasin, agricultural drains are an important water source for irrigators, Tule Lake, and the Lower Klamath Lake National Wildlife Refuge. An agricultural-drain flow analysis indicates that groundwater flow to drains has decreased substantially since 2000.  Model results for the Tule Lake subbasin indicate that increased supplemental pumping is the main stress on the groundwater system in the area. 

Throughout the Klamath Basin, increased use of groundwater combined with drought and climate change have decreased groundwater levels. In some parts of the basin, groundwater levels have declined as much as 30 ft. since 2001. These declines have been concerning for people who rely on shallow private wells for household needs. USGS monitoring and research on the groundwater-flow system will remain important to future considerations by resource managers, local citizens, and Tribal partners.