Water Resources of the Tulalip Indian Reservation

Science Center Objects

Future increases in population and development of the Tulalip Indian Reservation and neighboring areas would lead to increased pumping of ground water both on and off the Reservation. Increased pumpage in coastal and inland wells may decrease baseflows of streams and could affect fish-rearing operations in the Tulalip Creek watershed.

9722-9EM - Water Resources of the Tulalip Indian Reservation, Snohomish County, Washington - Completed FY2004

Problem - Future increases in population and development of the Tulalip Indian Reservation and neighboring areas would lead to increased pumping of ground water both on and off the Reservation. Increased pumpage in coastal and inland wells may decrease baseflows of streams and could affect fish-rearing operations in the Tulalip Creek watershed.

Objectives - The objectives of the study are to evaluate the current ground-water and surface-water resources of the Tulalip Indian Reservation and to estimate some of the possible effects of increased development on those resources.

Relevance and Benefits - Proposal elements with significant scientific value for Washington State include 1) improving ground-water recharge estimates using the chloride mass-balance method, and 2) improving knowledge of the subsurface hydrogeology of the study area. A more detailed explanation of their significance follows:

1. Independent estimates of ground-water recharge using the chloride mass-balance method provides information that can be used to help refine regression equations that are currently used to estimate ground-water recharge in the Puget Sound lowlands of Washington State. Improved estimates of aquifer recharge is key to estimating long-term ground-water availability.

2. Improving knowledge of the subsurface hydrogeology in the study area will help in the future with the construction of a detailed hydrogeologic framework for the Puget Sound Lowlands. A detailed framework will help to better understand ground-water availability in the Puget Sound Lowlands.

Approach - To evaluate the current water resources, the water budget for the study area developed by Drost (1983) will be updated by improving estimates of ground-water recharge, by determining current streamflow conditions, and by incorporating current water-use estimates. Hydrogeology maps will be developed that show the extent of the aquifers beneath the Reservation. To evaluate possible effects of development on the water resources, the possible future ground-water use will be estimated.