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Research about Douglas County, Nevada

Source-linked reports with geographic coverage including Douglas County, Nevada.

7 recordsLinked to original sources
USGS2013

The distribution and modeling of nitrate transport in the Carson Valley alluvial aquifer, Douglas County, Nevada

Residents of Carson Valley in Douglas County, Nevada, rely on groundwater from an alluvial aquifer for domestic use and agricultural irrigation. Since the 1970s, there has been a rapid increase in population in several parts of the valley that rely on domestic wells for drinking water and septic systems for treatment of household waste. As a result, the density of septic systems in the developed areas is greater than one septic system per 3 acres, and the majority of the domestic wells are shallow (screened within 250 feet of the land surface). The distribution of nitrate as nitrogen (referred to herein as nitrate-N) concentrations in groundwater was determined by collecting more than 200 samples from 8 land-use categories: single family residential, multifamily residential, rural (including land use for agriculture), vacant land, commercial, industrial, utilities, and unclassified. Nitrate-N concentrations ranged from below detection (less than 0.05 milligrams per liter) to 18 milligrams per liter. The results of nitrate-N concentrations that were sampled from three wells equalled or exceeded the maximum contaminant level of 10 milligrams per liter set by the U.S. Environmental Protection Agency. Nitrate-N concentrations in sampled wells showed a positive correlation between elevated nitrate-N concentrations and the percentage of single-family land use and septic-system density. Wells sampled in other land-use categories did not have any correlation to nitrate-N concentrations. In areas with greater than 50-percent single-family land use, nitrate-N concentrations were two times greater than in areas with less than 50 percent single-family land use. Nitrate-N concentrations in groundwater near septic systems that had been used more than 20 years were more than two times greater than in areas where septic systems had been used less than 20 years. Lower nitrate-N concentrations in the areas where septic systems were less than 20 years old probably result from temporary storage of nitrogen leaching from septic systems into the unsaturated zone. In areas where septic systems are abundant, nitrate-N concentrations were predicted to 2059 by using numerical models within the Ruhenstroth and Johnson Lane subdivisions in the Carson Valley. Model results indicated that nitrate-N concentrations will continue to increase and could exceed the maximum contaminant level over extended areas inside and outside the subdivisions. Two modeling scenarios were used to simulate future transport as a result of removal of septic systems (source of nitrate-N contamination) and the termination of domestic pumping of groundwater. The models showed the largest decrease in nitrate-N concentrations when septic systems were removed and wells continued to pump. Nitrate-N concentrations probably will continue to increase in areas that are dependent on septic systems for waste disposal either under current land-use conditions in the valley or with continued growth and change in land use in the valley.

Nevada↗
USGS1996

Trends in chloride, dissolved-solids, and nitrate concentrations in ground water, Carson Valley and Topaz Lake Areas, Douglas County, Nevada, 1959-88

Rapid population growth in Douglas County, an area of approximately 750 square miles in west-central Nevada, has led to concern about the present and future effects of development on ground water. This report describes the results of two nonparametric statistical procedures applied to detect trends in concentrations of chloride, dissolved solids, and nitrate in ground water. The water-quality data consist of analytical results from ground-water samples collected and analyzed by the U. S. Geological Survey and ground-water-quality data provided by the Nevada Bureau of Health Protection Services for the Carson Valley and Topaz Lake areas of Douglas County, Nevada. For purposes of this study, statistical significance, expressed as the p-value, was set at 0.1. The Mann-Whitney-Wilcoxan rank-sum test detected increasing step-trends for nitrate in one of seven residential areas and for dissolved-solids concentrations throughout the study area. Decreasing step-trends for chloride and dissolved-solids concentrations were detected in the west Carson Valley area. Kendall's Tau detected monotonic trends for increasing nitrate concentrations at four domestic wells and for increasing dissolved-solids concentrations at two domestic wells. No other statistically significant trends were indicated by either test. Land-use relations to areas where increasing trends were detected suggest that the density of individual wastewater-treatment systems may exceed the capacity of soils to treat wastewater leachate.

Nevada↗
USGS1989

Ground-water quality in Douglas County, western Nevada

A 182% increase in population within the last 10 years in Douglas County, Nevada, has raised concerns by county officials as to the possible effects land development may have on groundwater quality. Most groundwater in Douglas County meets the State of Nevada drinking water standards. Of the 333 water samples used in this analysis, 6 equaled or were greater than the drinking water standards for sulfates, 44 for fluoride, 4 for dissolved solids, 5 for nitrate as nitrate, 12 for arsenic, 33 for iron, and 18 for manganese. Groundwater in the west-central, northern, and northeastern part of Carson Valley is influenced by geothermal water. Some areas in the county may have septic-tank effluent contaminating the groundwater. Temporal changes in most municipal wells showed no overall trend for dissolved-solids and nitrate concentrations spanning the years 1969-83. However, a municipal well in the Topaz Lake area has shown a general increases in the nitrate concentration from 1961 to 1984, but the concentration does not exceed the drinking-water standard. A future groundwater quality monitoring program in Douglas County would include periodic sampling of primary or heavily pumped wells, long-term trend wells, and supplemental wells. (Thacker-USGS)

Nevada↗
USGS1988

Simulated changes in ground-water flow caused by hypothetical pumping in east Carson Valley, Douglas County, Nevada

An existing groundwater model of Carson Valley was used to simulate changes in groundwater flow on the east side of Carson Valley, Nevada, in response to hypothetical increases in groundwater pumpage. Pumpage scenarios that reflect State groundwater permits and pending applications were used in four different simulations to estimate the effect of hypothetical development on groundwater levels and storage, groundwater flow to the Carson River, and groundwater levels and storage, groundwater flow to the Carson River, and groundwater consumed by evapotranspiration over a 45-yr period. The four simulations were based on pumpage rates ranging from 0.13 to 6.4 cu ft/sec (92 to 4,590 acre-ft/year). Changes in groundwater flow and water levels caused by the lowest rate were minimal and at the limit of accuracy of the groundwater model. The highest pumping rate caused water level declines as much as 15 ft, decreased groundwater storage by 27,000 acre/ft, decreased groundwater to the Carson River by 4.3 cu ft/sec (3,100 acre-ft/year), and reduced evapotranspiration losses by about 1,200 acre-ft/year. (Author 's abstract)

Nevada↗
USGS1982

Ground-water levels and water quality in an area near Topaz Lake, Douglas County, Nevada

Intensive residential development of land along the northwest shore of Topaz Lake has raised concern regarding the adequacy of the water supply and possible effects of septic-tank effluents on the quality of local ground water and the lake. Existing data on water levels, well construction, and water quality were compiled, and a limited program of water-level measurement and water-quality sampling was conducted during 1976-77 to provide documentation of current hydrologic conditions against which effects of future development may be measured. Water-level measurements show the presence of small independent aquifers near the periphery of the alluvial fan covering the study area and a main alluvial aquifer in which water levels fluctuate in direct response to annual changes in lake stage. The sampled ground water can be grouped into four chemical types--three based on the relative proportions of sulfate and bicarbonate and one based on an increased proportion of chloride plus nitrate. Frequency distributions of the observed occurrences of nitrate (as NO3), phosphate (as PO4), and chloride in ground water indicate thresholds for background concentrations of these constituents at 0 to 3, 0 to 0.35, and 0 to 6 milligrams per liter, respectively. Above-background concentrations of nitrate and phosphate in ground water may be attributable, in part, to natural sources of these constituents; however, septic-tank effluents have increased the concentrations of nitrate, chloride, and perhaps phosphate in at least two areas of the current development. Sampling for dissolved organic carbon and coliform bacteria in ground water detected no contamination by these potential indicators of pollution.

Nevada↗