Seepage Study on Eastern Snake River with RiverCat

July, 2002 - Idaho Power Corporation (IPC) began a stream gauging program in 1996 that today has grown to well over 80 weather, water-storage, and stream-flow monitoring sites. One of the many projects that IPC has been involved with is a field data collection effort in support of the general "Eastern Snake Hydrologic Modeling Committee" strategy to refine and enhance conceptual and computer models of the Eastern Snake River Plain (ESRP) hydrologic system. The specific objective of this study is to measure gains from, and losses to, ground water (seepage) in selected river reaches in the ESRP during five detailed seepage studies.

Table 1 provides the results from a portion of one of the seepage studies. All the sites in this subsection were measured entirely using a SonTek/YSI 3.0-MHz RiverCat system (mounted to a hard-shell kayak; Figure 1) to determine the groundwater seepage rates and trends between two U.S. Geological Survey stream gauging stations.

The RiverCat was ideal for measurement in the areas selected because access to these sites by larger boats would be very difficult. Also, the compact nature of the RiverCat and the shallow stream depths at these sites made the system the preferable option.

IPC was able to detect relatively small seepage rates into or from the Snake River along this reach. In addition, discharges measured by the RiverCat were highly repeatable and consistent with each USGS gauging station.

Figure 2. Discharge data collected
using RiverSurveyor software

• RiverCat