Hydrologic Setting and Conceptual Hydrologic Model of the Walker River Basin, West-Central Nevada

Abstract

Plate 1. Map showing water-table contours in Smith Valley, Mason Valley, and lower Walker River basin, autumn 2006. during the 2005 spring runoff which followed a 5-year drought. No additional losses were measured during 2006 even though there was continuous flow, indicating bank and aquifer storage had been filled. Water-table contours and upward vertical gradients indicate Walker Lake is the final discharge point for groundwater in the lower Walker River basin. Purpose and Scope This report describes the hydrologic setting of the Walker River basin and a conceptual hydrologic model of the relations among streams, groundwater, and Walker Lake. The report emphasizes the lower Walker River basin from the streamflowgaging station Walker River near Wabuska, Nev. (Wabuska gage, 10301500; fig. 4), to the Hawthorne Army Ammunition Depot (Army Depot) near Hawthorne, Nev. (fig. 1). Surfacewater/groundwater interactions and groundwater flow directions in Smith and Mason Valleys, the most agricultural part of the Walker River basin, also are described. Data were collected from 2004 through 2008.

Simulation of the Lower Walker River Basin hydrologic system, west-central Nevada, using PRMS and MODFLOW models

“…Groundwater altitudes adjacent to Walker Lake are higher than the lake level (Lopes and Allander, 2009a), which indicates that the general direction of groundwater flow is towards Walker Lake and that groundwater generally discharges to the lake. When Walker Lake level rapidly rises, which occurs with large inflows from the Walker River, the hydraulic gradient likely reverses, so that lake water flows outward into the groundwater system.…”

“…However, not much is known about the geometry and thicknesses of the hydrogeologic units, and development of a detailed hydrogeologic model of the lower Walker River Basin was beyond the scope of this project. A summary of the hydrogeology of the lower Walker River Basin is provided by Lopes and Allander (2009a). The discussion that follows is a brief summary of the "Hydrogeologic Units" section from Lopes and Allander (2009a) but modified to pertain specifically to this work.…”

“…A summary of the hydrogeology of the lower Walker River Basin is provided by Lopes and Allander (2009a). The discussion that follows is a brief summary of the "Hydrogeologic Units" section from Lopes and Allander (2009a) but modified to pertain specifically to this work.…”

“…Following extended periods when the lowest reach of Walker River below Lateral 2A is dry, substantial losses of streamflow can occur as the channel is rewetted and recharges the local groundwater system. Lopes and Allander (2009a) estimated a net loss of 8,000 acre-ft along this reach in 2005 after flows rewetted this reach of the river following a drought period of about 5 years.…”

“…Some groundwater is lost through outflow through the basin boundary near Double Springs, is pumped, or discharges to streams. The movement of groundwater in the lower Walker River Basin is described in detail by Lopes and Allander (2009a).…”