Borax Lake is located in southeastern Oregon, within the Alvord Valley Known Geothermal Resource Area. Borax Lake is a large hot spring; there are more than 50 smaller hot springs within about one-half mile to the north of the lake. Several geothermal exploration wells have been drilled near Borax Lake, and there is concern that development of the geothermal resources could affect the lake and nearby hot springs. A factor to consider in developing the resource is that the Borax Lake chub is an endangered species of fish that is found exclusively in Borax Lake.

This study was designed to collect basic hydrologic data to develop a long-term monitoring plan. Baseline data, collected before geothermal production wells are used extensively, will provide an understanding of natural trends and will help identify change caused by development.

Basic data collected during reconnaissance field visits to the area included spring temperatures, specific conductances, and discharge; field measurements in wells included water-level measurements and temperature, specific conductance, and discharge measurements in flowing wells. The study of the Borax Lake area included depth and temperature measurements in the vent area of the lake, point velocity measurements, underwater video photography, and an evaluation of methods to measure discharge from the lake. Water-quality samples were collected at Borax Lake, one hot spring, and one flowing well.

Information from field visits was used to develop a monitoring plan. The plan would include monitoring Borax Lake by measuring discharge, stage, evaporation, temperature, and specific conductance; water-quality sampling and analysis; and monitoring shallow ground-water levels near Borax Lake using shallow piezometers. Minimally, one hot spring in North Borax Lake Spring Group 1 would be monitored for temperature and specific conductance and sampled for water-quality analysis. In addition, two flowing wells would be monitored for water levels, temperature, specific conductance, and discharge and sampled for water-quality analysis. The construction characteristics of these wells must be verified before long-term data collection begins. In the future, it may be helpful to monitor shallow and (or) deep observation wells drilled into the thermal aquifer to understand the possible effects of geothermal development on Borax Lake and nearby springs.