Science Center Objects

Island County consists of two major islands, Whidbey and Camano, and lies in northern Puget Sound, north of Seattle. Whidbey Island has an area of about 165 square miles and Camano Island an area of about 45 square miles, for a total area of about 210 square miles. Ground water is the primary source of water on the islands, and the ground-water system is fairly well understood, due in part to studies of Island County conducted in the 1980s by the U.S. Geological Survey and others. However, some questions still remain about the ground-water system of Island County, especially the quantity of recharge reaching the ground-water system from precipitation.

9722-A4H - Ground-Water Recharge Characteristics of Island County, Washington - Completed FY2003

Problem - Island County consists of two major islands, Whidbey and Camano, and lies in northern Puget Sound, north of Seattle. Whidbey Island has an area of about 165 square miles and Camano Island an area of about 45 square miles, for a total area of about 210 square miles. Ground water is the primary source of water on the islands, and the ground-water system is fairly well understood, due in part to studies of Island County conducted in the 1980s by the U.S. Geological Survey and others. However, some questions still remain about the ground-water system of Island County, especially the quantity of recharge reaching the ground-water system from precipitation.

Objectives

  1. Estimate the total amount and the areal distribution of recharge entering the ground-water system on each of the two islands.
  2. Identify potential areas for using runoff to artificially recharge the ground-water system.

Relevance and Benefits - The proposed work provides an opportunity to assemble data that will increase the understanding of the hydrologic system of Island County. In addition, the data and interpretations associated with the study will aid county and state agencies in making planning and management decisions. Specific benefits to the USGS include collection of additional information regarding the hydrologic system of Island County, which, in turn, may be applicable to other islands in Puget Sound.

Approach

  1. Ground-water recharge cannot be measured directly and is difficult to estimate accurately. The estimates can be subject to large errors; consequently, multiple methods should used to verify estimates and provide some idea of the error in them. Therefore, two methods will be used to estimate recharge:
    • water-budget recharge model, utilizing meteorological and various recharge-related data, and
    • chloride mass-balance method.
  2. As part of the distribution of recharge determined using the recharge model, a distribution of runoff will be estimated. This distribution, in conjunction with the appropriate geology and soils data, will be used to identify areas where artificial recharge could be considered.