USGS OFR 2005-1329 Ground-Water Reconnaissance of the Bijou Creek Watershed, South Lake Tahoe, California, June

Ground-Water Reconnaissance of the Bijou Creek Watershed, South Lake Tahoe, California, June–October 2003

By Kip K. Allander

Report availability: Portable Document Format (PDF).

Abstract

A ground-water reconnaissance study of the Bijou Creek watershed in South Lake Tahoe, California was done during the summer and early fall of 2003. This study provides basic hydrologic data for a region in the Lake Tahoe Basin in which a continuing loss of lake clarity is occurring in the nearshore zone of Lake Tahoe. Wells, springs, and a surface-water site were located and basic hydrologic data were collected. Water levels were measured and water samples were collected and analyzed for nutrients. Measurements of water temperature, specific conductance, and pH were made at all ground-water sites where possible and at one surface-water site.

Organic nitrogen plus ammonia, ammonia, and biologically-available iron concentrations generally were greater in the ground water in the Bijou Creek watershed than those observed in ground water elsewhere in the Lake Tahoe Basin. Nitrate concentrations were similar in the two groups. Phosphorus and orthophosphate concentrations generally were lower in the ground water of the Bijou Creek watershed compared to ground water from elsewhere in the Lake Tahoe Basin. Specific conductance and pH of ground water were similar between the Bijou Creek watershed and the Lake Tahoe Basin, but the temperature of ground water was generally greater in the Bijou Creek watershed.

Nitrate concentrations appeared to increase over time at one of two long-term ground-water sites. Orthophosphate concentration decreased while specific conductance increased at one of the two sites, but no trend was detected at the other site for either parameter. No trends were detected for phosphorus, biologically-available iron, water temperature, or pH at either of the long-term sites. Trends in ammonia and organic nitrogen plus ammonia concentrations were not evaluated because a majority of the values were below the method detection limits.

There were no obvious spatial distribution patterns for nutrient concentrations or field parameters in the Bijou Creek watershed. The altitude of the ground-water table above sea level generally increased with increasing distance from Lake Tahoe. The altitude of the ground-water table was greater than the altitude of the surface of Lake Tahoe except at one ground-water site which is influenced by a cone of depression around a nearby production well. Ground water in the Bijou Creek watershed discharges to Lake Tahoe and may contribute to the higher than normal turbidity in the area.

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