2007-516-00

Enhancing Summer Instream Flow and Reducing Temperature in Agricultural Watersheds

The project is innovative because (1) it proposes a new concept for storing winter excess precipitation by enhancing infiltration and reducing runoff in agricultural watersheds via adoption of direct-seeding practices, (2) the new concept has potential to enhance summer flow as the infiltrated water will gradually percolate through the soil to aquifer system available for use in later (including summer) time, (3) the innovative approach brings multiple habitat benefits as the reduced runoff in winter will lead to less soil erosion and the enhanced stream flow will alleviate the problem of high stream temperature in summer, (4) the approach creates a win-win scenario as farming will become the habitat solution rather than the problem, (5) compared with other ground-water recharge options, this approach can be easily implemented as the practice has already been recognized as among the optimum management practices for water quality protection, and (6) the method has not been applied to fish or wildlife management for the purpose of flow enhancement. Low summer instream flow and associated high water temperature are two critical impairments of salmon habitats in the Pacific Northwest. The low stream flow is mainly caused by the climatic pattern of the region where little precipitation occurs in summer when the water resource is in great demand and the majority of the precipitation occurs in winter resulting in excessive surface runoff. An increase in water availability during the summer can be achieved by altering the hydrological imbalance. For the mainstems of the Snake and Columbia Rivers, this is achieved by flow regulation using reservoirs created by dams. However, limited options are available for maintaining stream flow in the tributary areas where juvenile fish spend the critical period of their life history.

The goal of this innovative research project is to investigate the potential for increasing instream flow and ground-water resources through a wider adoption of direct-seeding as an alternative agricultural management practice. Ground-water flow is a gradual process with an extremely long duration, creating a natural mechanism of water resource enhancement. We believe the vast space in soil zone near the land surface and the underlying aquifers can be used to store water during winter and spring, and the water stored will flow naturally into the streams. If the approach is proven effective, the function of ground-water storage is equivalent to that of reservoirs except that water movement is regulated by the hydraulic conductivity of the soil and the head difference between the water table and the stream surface. These subsurface reservoirs, however, are created naturally rather than artificially. The strategy offers a natural way to alter the hydrological imbalance and may have a great potential to become one of the most effective and economical options in the tributary areas. Our previous research results show that land management practice, such as direct-seeding, considerably enhances field infiltration, and therefore has a great potential for increasing recharge to these subsurface reservoirs.

The proposed work includes determination of the infiltration characteristics of agricultural land under different management practices, and investigating the flow and release of infiltrated water to streams through modeling and field verifications. This project is “on-the-ground-demonstration” or “pilot” in nature as it builds upon the fact that farmers have increasing interests in adopting direct-seeding practices. This project will be conducted with the collaboration of Pomeroy Conservation District in the Pataha Watershed, a model watershed designated by the Bonneville Power Administration. Washington State University will have the primary responsibility for performing the work with assistance from the conservation district. The outcome of the project will have a region-wide impact by improving habitats for not only salmon, but also resident fish.

None

2008

2017

Timmie Mandish (Inactive)

Closed - Project Status Report

Province	Subbasin	%
Columbia Plateau	Tucannon	100.00%

Habitat

Restoration/Protection

Trout, Bull

Anadromous: 0.0%   Resident: 100.0%   Wildlife: 0.0%

WA - by WE Location Expenditure (Public Tags)

None

None