Author: Christina M. Gearhart

Publisher:

Published: 2001

Total Pages: 212

ISBN-13:

"As part of the ongoing Environmental Protection Agency Wellhead Protection Demonstrations Project grant number X-000465-05, an examination of the physical interactipn between the Spokane River and the Spokane aquifer has been completed. This study has established effluent and influent reaches of the Spokane River between State Line, Idaho and the city of Spokane, Washington. Five study sites were established for this project: the State Line site, the Barker Road site, the Sullivan Road site, the Upriver Dam site and the Mission Avenue site. The State Line and Barker Road sites are influent, with unsaturated flow. The Sullivan Road, Upriver Dam and Mission Avenue sites are connected by saturated flow with influent and effluent conditions present at different times of the year. Based on the observations within the five sites, the Spokane River was divided into five reaches and assigned an unsaturated, saturated or transitional flow character. Reaches 1 (from State Line to Harvard Road) and 2 (from Harvard Road to Barker Road) are unsaturated reaches. Reach 3 (from Barker Road to Sullivan Road) is the transitional reach. Reaches 4 (from Sullivan Road to Trent Avenue) and 5 (from Trent Avenue to the Plantes Ferry footbridge) are saturated reaches. Darcy's equation was used to calculate volumetric flux between the river and the aquifer. For low flow unsaturated conditions, the Spokane River loses 104.0 cfs (2.94 ems) between the State Line and Sullivan Road. For high flow conditions, this reach loses 570.8 cfs (16.15 ems). For saturated low flow conditions, the Spokane River gains as much as 116.4 cfs (3.29 ems) and loses as much as 204.5 cfs (5.79 ems) between Barker Road and Plantes Ferry Park. With high flow saturated riverbed coverage, this same reach gains as much as 473.77 cfs (13.41 ems) and loses as much as 832.33 cfs (23.55 ems). Discharge measurements performed by the Spokane County Conservation District during the study period indicate that the Spokane River is influent between the Post Falls Dam and Barker Road. As flows in the river increase, the amount of flow lost to the aquifer also increases. Between Barker Road and the Plantes Ferry Footbridge the character ofthe river is opposite; the river showed gains during all measurements. As flows increase, however, the river gains less from the aquifer."--Document.