USGS Washington Water Science Center
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WA238 - Hydrologic Summary of Spokane Area, Washington, for Planners - Completed FY1985
Problem - The water supply for Spokane and surrounding area is obtained principally from a highly permeable aquifer which underlies the area. A 1977 U.S. Geological Survey (USGS) study resulted in a report which was used by Environmental Protection Agency (EPA) in their justification for sole-source designation of the aquifer. Following this the District undertook and recently completed a study with Spokane Co. to (1) quantify the ground-water flow system, (2) determine water movement between the rivers and the Ground-Water (GW) system, (3) map water quality in the aquifer, and (4) estimate chloride loadings to the aquifer from various land uses. A significant amount of technical information has been generated for this area and there is an immediate need to present the information in a format that can be understood by both planners and the general public.
Objectives - To depict in a series of maps and graphs the hydrology of the area. In general, the illustrations would show (1) the surface-water system, (selected flood-prone areas of frequency and flow-duration analysis of instream flows, water chemistry trends); (2) the GW system (areal extent of the aquifer, depth to water, water-level contours, hydrographs, estimated saturated thickness map, calculated septic-tank and irrigation chloride loadings, point source locations and calculated chloride loadings, areal distribution of dissolved solids, chloride, and nitrate-nitrogen); and (3) GW-SW relationships (maps showing velocity and direction of GW system and gaining and losing reaches of river). Each map would have a brief narrative describing the information presented in non-technical terms.
Approach - The data needed to compile such maps are presently available within the Washington District. Compilation and organization of the data into the above listed maps will require data retrieval and subsequent plotting and map preparation into a format similar to that used for the Puget Sound Land Information Analyses (LIA) Project.
WA203 - Evaluation of Contaminant Movement in the Unsaturated Zone of the Spokane Gravel Aquifer - Completed FY1981
Problem - The Spokane Valley is an urbanized area of about 250,000 people. It is underlain by a highly permeable water table aquifer which is a major source of agricultural, industrial, and municipal water supply. The aquifer's high permeability makes it vulnerable to contamination from man's activities. Because it is a principal source of water in this area, protection of the water quality is mandatory. Present water quality data are sparse. Two previous studies have resulted in contradicting reports, leaving the decision-makers no firm basis on which to plan for protection of the aquifer. The USGS is developing a mass transport model to describe the movement of selected constituents in the aquifer and predict future trends based on proposed management alternatives. However, the problem of movement of potential contaminants from the land surface to the water table is not being addressed. This project will address that problem.
Objectives - Define the fresh water table aquifer boundaries, hydraulic properties, and actual water withdrawals on a monthly basis. Develop a digital model of the aquifer to simulate planned aquifer development schemes.
Approach - District personnel will conduct an extensive literature search and enlist the technical assistance of other Division personnel. A test site will be selected based on representativeness of the area, vicinity of other septic tanks, suitability for lysimeter placement, depth to water, and availability of a sufficiently large septic tank drainfield to tap into. Elution tests will be conducted on soil samples--these data will be used to determine sampling frequency and will be used in the development of a solute-transport model. Several wells will be drilled to water and lysimeters will be installed. Background data will be collected for several months; then a drainfield will be constructed over the lysimeter placements and connected into a large existing septic tank. A tracer metering device will be connected into the head of the drainfield.
WA200 - Evaluation of Ground-Water Quality in the Spokane Basin - Completed FY1981
Problem - A highly permeable aquifer in the Spokane basin is the principal source of water for agricultural, municipal, and domestic use. The present water quality and the potential for contamination are poorly known but planning decisions affecting the water quality need to be made.
Objectives - Gain a reasonably detailed knowledge of the present water quality, assess the cause of variations in quality, and determine the means of predicting or projecting the movement of introduced contaminants in space and time.
Approach - Chemical and water-quality data will be collected from 185 existing wells plus 15 test wells to be drilled; land use and surficial materials maps will be prepared; a water-quality model will be coupled with an existing ground-water flow model to simulate movement of contaminants; and a monitoring network will be designed and implemented.
WA168 - Water Resources of the Spokane River Basin in Washington - Completed FY1978
Problem - The Spokane River Basin contains an extensive gravel aquifer whose geometry is poorly defined. Flow through this aquifer has been estimated to average 1,200 CFS. Extensive industrial, municipal, and irrigation developments in and near Spokane, Washington use large quantities of water from this aquifer. Despite several previous studies, a quantitative evaluation of this aquifer remains to be accomplished. For example, overdevelopment is very possible under present trends. There is also a potential for contamination of this aquifer by man's activities on the land surface.
Objectives - The objectives of this project are to accurately determine the hydraulic characteristics of the aquifer, including its geometry (especially in the primary recharge and discharge areas), to develop a model of the flow system that will provide a basis for guiding management decisions and development of the aquifer, and provide a basic model upon which a water-quality model may be superimposed at a later date to develop an understanding of the possible effects of various waste-disposal and land-use practices.
Approach - Emphasis in data collection will be on: (1) drilling and geophysical surveys to determine aquifer geometry; (2) water-level distribution in, and pumpage from the aquifer; (3) determination of inflow from adjacent highlands, (4) determination of transmissivity and storage values from pumping tests, and (5) determination of the hydraulic connection between surface and ground waters.