Baseline hydrologic studies in the lower Elwha River 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.
Study Area
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Baseline hydrologic studies in the lower Elwha River prior to dam removal |
| Series title | Scientific Investigations Report |
| Series number | 2011-5120-4 |
| DOI | 10.3133/sir201151204 |
| 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 |
| Google Analytic Metrics | Metrics page |