National Water-Quality Assessment Program (NAWQA) -- Nevada Basin and Range Study Unit
A significant number of ground water studies will take place in FY03. Table 1 summarizes the work that will be done. Below are brief descriptions of the work.
We have two interrelated ground-water studies in the Reno/Carson City areas planned for FY03. These are: 1) re-sampled Major Aquifer Study (MAS) in Reno and Carson City that will sample 30 wells, and 2) Source Water Assessment (SWA) study in Carson City and Spanish Springs that will sample 15 public supply wells. These two studies complement the Urban Land Use Study that was conducted in Reno and Carson City in FY02.
The MAS will re-sample wells from Cycle I (where available) to determine trends in water quality over time in these aquifers. Where previously sampled wells are not available, new wells will be chosen as close to the previously sampled wells as possible. Reconnaissance of these areas suggests that approximately 10% of the previously sampled wells are no longer available for sampling in the MAS study area. The SWA study will sample the top producing wells in Spanish Springs and Carson City. This sampling will begin in October 2002.
We will be sampling 30 wells in the carbonate aquifer system east and north of Las Vegas in both Nevada and Utah. The carbonate aquifer is likely to be a significant source of water for the Las Vegas and Salt Lake City areas in the future, and it is important to obtain baseline data before exploitation begins. This work will require down hole pump setting because some of the wells are over 1000 feet deep. The sampling will also take place in relatively remote places, but will be conducted in conjunction with the Great Salt Lake NAWQA unit, so that sampling teams won’t have to travel too far.
Because we know very little about recharge, flow paths and age of the water in the carbonate aquifer, we are requesting additional funds from the Las Vegas Valley Water District for stable isotope measurements on all wells and Carbon-14 measurements of dissolved organic carbon in order to fully characterize the aquifer system from recharge to discharge areas.
The Nevada Basin and Range Study Unit will participate in the Transport of Anthropogenic and Natural Contaminants (TANC) topical team study that will use retrospective data from public supply wells in Carson City and Spanish Springs to delineate sources and flow directions of contaminants such as arsenic, nitrate, and MTBE. Computer steady state flow models will be developed to determine capture zones of the public supply wells and determine how vulnerable these wells are to contamination. This study will be completed by the end of FY03.
The Carson Water Subconservancy District funds this project as a cooperative study to look at water quality changes over time in the Carson Valley. Over 20 years of nitrate and total dissolved solids (TDS) data from over 30 wells are available through out the valley. This study is evaluating the impact of different land uses on the nitrate and TDS trends. Statistical analysis has been conducted on all of these wells and extensive GIS analysis has been undertaken of the land uses and well distribution. A more detailed summary of the work can be found at <http://nevada.usgs.gov/activities/nv240.htm>.
Table 1. Groundwater studies planned for FY03.
A variety of surface water and ecology studies will take place in FY03. Table 2 summarizes the work that will be done. Below are brief descriptions of the work.
Sampling for trend analysis is planned for the three sites established for the Cycle I study. These sites are 1) Las Vegas Wash near Las Vegas, NV, 2) East Fork Carson River near Dresslerville, NV, and 3) Truckee River at Clark, NV.
Las Vegas Wash is essentially an artificially perennial stream supported by urban irrigation returns, ground-water discharge, and occasional storm water inputs. Thus water quality of the wash is degraded. The city of Las Vegas has plans to enhance the water quality of the wash by installing detention dams and artificial wetlands along the course of the wash to try to improve water quality entering Lake Mead. Our site is located up-gradient of most of this work and will provide a key indicator of background water quality conditions in the wash that can be used to assess whether these improvements are working.
The East Fork Carson River at Dresslerville was selected as a new reference trend site. The NVBR team feels this is a good reference site, although there are some upstream diversions and possible effects from tributary inflow from the Leviathan Mine Superfund site and the town of Markleeville. The site is located up gradient of almost all of the urban and agricultural development in the Carson Valley and provides the relatively pristine reference site in the Carson and Truckee basins.
Table 2. Surface water and ecology studies planned for FY03.
The Truckee River site at Clark, located approximately 12 miles east of Sparks, is the basin integrator site for the basin that includes heavily urbanized areas in Reno and Sparks and agricultural runoff from Washoe Valley. The Truckee River is the most important river in NVBR, providing most of the drinking water in the Reno metro area, irrigation water to downstream agriculture, and flows for the endangered Lahontan Cutthroat Trout that lives in Pyramid Lake and spawns in the Truckee River. The site will continue to be monitored and, along with coring at Pyramid Lake or Lahontan Reservoir in FY04, will be used to evaluate trends in water quality of the basin.
Water samples at each trend site in FY03 will be collected 21 times (including blanks and replicates) at the Urban site, 21 times (including blanks and replicates) at the integrator site, and 14 times (including blanks and replicates) at the reference site. Samples at Las Vegas Wash (Urban site) will be collected at least monthly, and but will be collected twice a month in November, January, March, May, July, and September. Samples at Clark (Integrator site) will be collected at least monthly, but will be collected twice a month during surface water runoff (May to August) and in October. Samples at Dresslervile (Reference site) will be collected monthly.
Installation of automated loggers for continuous collection of specific conductance and temperature was completed in FY02 at the existing three trend sites (Truckee River at Clark, Carson River and Garnerville (near Dresslerville) and Las Vegas Wash near Las Vegas). Data will be collected from these sites throughout FY03.
We will conduct single reach ecological sampling at Dresslerville and Clark trend sites in September of 2003. This sampling will be coordinated to occur after peak flows in the rivers in order ensure that we sample representative populations in the rivers.
We will be establishing a new fixed site to collect samples at the Chalk Bluff PWS intake. We will sample as close to the intake as possible. Nineteen samples will be collected over the fiscal year. A wide variety of parameters will be analyzed including pharmaceuticals and caffeine.
Planning for lake coring that will begin in FY04 will be done at the end of FY03. Sites in Pyramid Lake and possibly Lahontan Reservoir will be cored. This work will be coordinated with Pete Van Metre from the Texas District.
Table 3 is a preliminary schedule of tasks for FY03. Tasks include preparation and sampling of surface water trends sites on the Truckee River, Carson River and Las Vegas Wash, surface and ground water Source Water Assessments, one re-sampling Major Aquifer Study (MAS) in Reno/Carson City and Las Vegas, one new MAS in the Carbonate Aquifer (in conjunction with the Utah District), sampling of ecology in one reach on the Truckee and Carson rivers, topical team work for the TANC and ULUG studies, and planning for lake coring in conjunction with Pete Van Metre. If you have questions or want more information about one of the tasks, please contact the person(s) named as the lead for that task or contact Michael Rosen, Project Chief.
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