Howard A. Hanson Reservoir

Science Center Objects

The City of Tacoma relies on surface water stored in the Howard A. Hanson Reservoir, in the Green River Basin in King County, to meet municipal needs and demands. Reservoir managers must also consider how allocation and use of the resource are affected by ongoing activities in the basin associated with fisheries enhancement and by rules implemented under the Endangered Species Act for salmonid fish proposed for listing.

To help managers continue to improve reservoir management strategies, the USGS is developing four different linear equations to estimate or forecast at long-lead times the monthly mean reservoir inflows for the months of April through July. At the latest, the estimates need to be made by mid-January. Developing the equations involves exploring the relations between monthly inflows and climatic information, precipitation, and temperature, identifying important variables to be used in the regression equations, and developing a list of these variables for each of the inflow months.

WA440 - Estimating runoff season inflows to the Howard A. Hanson Reservoir, Green River, Washington - Completed FY2002

Problem and Needs - The City of Tacoma relies on surface water stored in the Howard A. Hanson Reservoir, Green River Basin, Washington to meet municipal needs and demands. These demands are growing and must be met by optimal use of the water resources. Ongoing activities in the basin for enhancement of fisheries and rules implemented under the Endangered Species Act for salmonid fish that are proposed for listing may affect the allocation and use of the resource. Additional tools are needed in order to improve reservoir management strategies.

Objectives - The objective of the study is to develop a means to estimate or forecast at long-lead times the monthly mean reservoir inflows for the months of April through July. At the latest, the estimates need to be made by mid-January. The estimates will be based on four different multi-linear regression equations.

Relevance and Benefits - The study addresses many issues identified in the Water Resources Division's strategic plan and the Districts priority program opportunities for meeting the Nation's needs. These issues include developing tools for effectively managing the Nation's watersheds and improving tools for transference to others. The assessment of availability of America's water is also an important issue. The study also addresses river-basin simulation. Last, the U.S. Geological Survey (USGS) is a neutral scientific party for providing information, and is building partnerships for developing and using methods to solve important problems that are common in the Nation.

Approach - The study will have three phases. The first phase includes preliminary exploration of the relations between the monthly inflows and climatic information, precipitation, and temperature. The second phase consists of identifying important variables that will be used in the regression equations, developing a list of these variables for each of the inflow months, and identifying the appropriate lead time to use with the variables. The last phase will be to develop regression equations to estimate the reservoir inflows.