Surface-water and groundwater interactions in the Big Lost River, south-central Idaho

Abstract

This is the second of three reports in a multichapter volume characterizing water resources in the Big Lost River Basin. These reports document the findings of a hydrogeologic investigation of the Big Lost River Basin that was jointly conducted by the U.S. Geological Survey, Idaho Department of Water Resources, and the Idaho Geological Survey from 2018 through 2021. Chapter A (Zinsser, 2021) describes the hydrogeologic framework of the Big Lost River Basin. It includes a conceptual definition of the hydrogeologic units, a three-dimensional hydrogeologicframework model, and a description of groundwater occurrence and movement. Chapter B (this report) describes streamflow gains from and losses to groundwater in the Big Lost River between Mackay Reservoir and south of Arco, Idaho. Streamflow gains and losses were estimated from a series of four surface-water measurement events during pre-and post-irrigation season conditions from 2019 to 2021. Chapter C will describe groundwater budgets for the Big Lost River Basin from 2000 to 2019. The groundwater budgets will provide annual estimates for aquifer inflows and outflows. Collectively, these reports present a characterization of water resources in the Big Lost River Basin that will help address current challenges in water-resource management.

Groundwater budgets for the Big Lost River Basin, south-central Idaho, 2000–19

“…This groundwater budget report is the third of three reports on water resources of the Big Lost River Basin; previous work is published in and Dudunake and Zinsser (2021). Collectively, these works provide an updated characterization of water resources in the basin and provide data and interpretation for water-resources decision making and future groundwater modeling.…”

“…The USGS, in cooperation with the IDWR, measured streamflow four times on the Big Lost River during the 2019-21 irrigation shoulder seasons (spring and autumn) (Dudunake and Zinsser, 2021) to document Big Lost River gains and losses. The method used for evaluating seepage in the groundwater budget differs from streamflow measurement events in that longer reaches between streamgages compiled over the irrigation season or calendar year (as applicable) are incorporated.…”

“…It includes a conceptual definition of the hydrogeologic units, a three-dimensional hydrogeologic-framework model, and a description of groundwater occurrence and movement. Chapter B (Dudunake and Zinsser, 2021) describes streamflow gains from and losses to groundwater in the Big Lost River between Mackay Reservoir and south of Arco, Idaho. Streamflow gains and losses were estimated from a series of four surface-water measurement events during pre-and post-irrigation season conditions from 2019 to 2021.…”

“…A 2007 study (Rice and Boyd, 2008) focused on seepage measurement in the Darlington Sinks area, indicating significant reach loses attributed to a local deep water-table condition. A part of the reach above the Moore Diversion consistently has measured gains based on streamflow measurement events that occurred in 2007 (Rice and Boyd, 2008) and 2019 (Dudunake and Zinsser, 2021).…”

“…The USGS installed five new streamgages in the basin and developed a hydrogeologic framework . In cooperation with the IDWR, the USGS hosted four, separate streamflow measurement events of the Big Lost River in spring and autumn during 2019-21 (Dudunake and Zinsser, 2021). The IDWR installed 18 new monitoring wells near the Big Lost River as nested well installations incorporated in the existing monitoring well network (IDWR, 2019(IDWR, , 2021a, and they completed a water-quality investigation (Womeldorph and Steimke, 2022).…”