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Baseline hydrologic studies in the lower Elwha River prior to dam removal: Chapter 4 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

Scientific Investigations Report 2011-5120-4

This report is Chapter 4 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal. For more information, see: Scientific Investigations Report 2011-5120
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Abstract

After the removal of two large, long‑standing dams on the Elwha River, Washington, the additional load of sediment and wood is expected to affect the hydrology of the lower river, its estuary, and the alluvial aquifer underlying the surrounding flood plain. To better understand the surface-water and groundwater characteristics of the river and estuary before dam removal, several hydrologic data sets were collected and analyzed. An experiment using a dye tracer characterized transient storage, and it was determined that the low‑flow channel of the lower Elwha River was relatively simple; 1–6 percent of the median travel time of dye was attributed to transient‑storage processes. Water data from monitoring wells adjacent to the main‑stem river indicated a strong hydraulic connectivity between stage in the river and groundwater levels in the flood plain. Analysis of temperature data from the monitoring wells showed that changes in the groundwater temperature responded weeks or months after water temperature changed in the river. A seepage investigation indicated that water from the river was moving into the aquifer (losing reach) between 1.7 and 2.8 kilometers from the river mouth. Surface‑water measurements and temperature and salinity data collected throughout the estuary helped to characterize the magnitude and nature of water movement in and out of the estuary. Salinity and stage sensors positioned in the estuarine network showed a strong surface‑water connection between the river and estuary waters east of the river. In contrast, there was a weaker connection between the river and estuarine water bodies west of the river.

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Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Baseline hydrologic studies in the lower Elwha River prior to dam removal: Chapter 4 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal
Series title:
Scientific Investigations Report
Series number:
2011-5120-4
Year Published:
2011
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Western Fisheries Research Center
Description:
36 p.
Larger Work Type:
Report
Larger Work Subtype:
USGS Numbered Series
Larger Work Title:
Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal (Chapter 2011-5120)
First page:
75
Last page:
110
Country:
United States
State:
Washington
Other Geospatial:
Elwha River