Boundary describes the extent of the Spokane Valley-Rathdrum prairie aquifer from south end of lake Pend Oreille, Idaho - thru Rathdrum Prairie, the Spokane Valley, turning north to discharge at little Spokane River, and Spokane river north and west of the city of Spokane. Source data overview:Spokane Valley aquifer (WA State only) digitized in 1988 by Spokane Co. Engineer Dept from USGS 1977 hydrologic study of the Spokane Aquifer. This layer digitized from 1:24000 quad maps into the County's GDMS GIS. The USGS relied heavily on contour lines that described the valley floor to delineate the Spokane aquifer boundary. The original boundary had the Spokane River as it's west edge, but was revised (by Bea Leckaff Spokane County WQMP-GIS) in June, 1994, under the direction of Stan Miller to include the flood plain terraces on the west side of the river, down to the Little Spokane River confluence. The extent of the aquifer was revised again in March, 1995 to reflect new information from CH2MHill aquifer studies being done for the City of Spokane (to support Wellhead Protection). The revised aquifer extends the influence of impervious basalt outcroppings from the Spokane Falls area to the Trinity Triangle, (Drumheller Springs). The corrections were made by BBL from information provided by Stan Miller.

Idaho Portion of the Aquifer data came from Idaho Panhandle Public Health GIS SCALE: Idaho data digitized originally from 1:24000 USGS maps LAST UPDATED: March 1993- received Idaho data and matched to Spokane county aquifer data.

Boundary describes the extent of the Spokane Valley-Rathdrum Prairie aquifer from south end of lake Pend Oreille, Idaho - through Rathdrum Prairie, the Spokane valley, turning north to discharge at little Spokane river, and Spokane river north and west of the city of Spokane. SOURCE DATA OVERVIEW: Spokane Valley aquifer (WA State only) digitized in 1988 by Spokane Co. Engineer Dept from USGS 1977 hydrologic study of the Spokane Aquifer. This layer digitized from 1:24000 quad maps into the County's GDMS GIS. The USGS relied heavily on contour lines that described the valley floor to delineate the Spokane aquifer boundary. The original boundary had the Spokane River as it's west edge, but was revised (by Bea Leckaff Spokane County WQMP-GIS) in June, 1994, under the direction of Stan Miller to include the flood plain terraces on the west side of the river, down to the Little Spokane River confluence. The extent of the aquifer was revised again in March, 1995 to reflect new information from CH2MHill aquifer studies being done for the City of Spokane (to support Wellhead Protection). The revised aquifer extends the influence of impervious basalt outcroppings from the Spokane Falls area to the Trinity Triangle, (Drumheller Springs). The corrections were made by BBL from information provided by Stan Miller.

Idaho Portion of the Aquifer data came from Idaho Panhandle Public Health GIS SCALE: Idaho data digitized originally from 1:24000 USGS maps LAST UPDATED: March 1993- received Idaho data and matched to Spokane county aquifer data.