Monitoring Sediment and Water Quality in Clear Creek
Science Center Objects
Clear Creek is a small alpine stream that begins near Lake Tahoe in the Sierra Nevada. The creek flows roughly parallel to U.S. Highway 50 and discharges to the Carson River near Carson City, Nevada. The Nevada Department of Transportation (NDOT) is concerned about how historical and ongoing development in the Clear Creek drainage basin has/is affecting Clear Creek and its sediment-transport characteristics. The USGS Nevada Water Science Center (NVWSC), in cooperation with NDOT, has been studying streamflow, sediment, and water-quality data from the creek since 2004. Discharge, sediment and selected water-chemistry data were collected and evaluated by the NVWSC for three Clear Creek sampling sites as part of the baseline study from water years 2004-07, and an interim study from water years 2010-12. The ongoing study (2013-16) continues the discharge, sediment, and selected water-chemistry data collection and evaluation.
Human activities, fires, and extreme precipitation events within the Clear Creek watershed have created erosion--which in some places is severe. Development in the middle and lower portions of the watershed has substantially increased urban and highway runoff and sediment entering Clear Creek. Salt application to roads during the winter also may be affecting water quality in the creek.
Clear Creek generally flows eastward along its approximate 12-mi length and discharges to the Carson River at an altitude of about 4,600 ft. The creek has 3 main perennial branches and several small intermittent tributaries originating from springs and seeps. NVWSC has collected daily streamflow in Clear Creek since 1948. Streamflow is monitored in real-time which provides early warning of high flows and gives NVWSC the ability to sample the creek during storm events.
For the purposes of the three studies, Clear Creek has been divided into three reaches. The data collection site is situated at the most downstream point on the creek within each reach.
- Site 1 represents the approximately 2.5 square miles of forested and undeveloped headwaters area of Clear Creek upstream of Highway 50. Site 1 serves as a background site free from most anthropogenic sources.
- Site 2 represents the reach of Clear Creek which extends almost 6 stream miles downstream of site 1 and an additional 13 square miles of drainage area. This middle portion of the watershed consists of mostly shrub/scrub vegetation, dense riparian vegetation, and low-density residential areas. This is also where USGS Gaging Station 10310500 is located.
- Site 3 is approximately 1.5 stream miles downstream of site 2. This lower reach represents and additional 2.7 square miles of drainage area and contains similar vegetation as the middle reach, with the addition of some urbanized and residential areas upstream of Highway 395.
Samples are collected from all three sites for the following:
- Daily streamflow will continue to be monitored at the gaging station on Clear Creek near Carson City.
- The Data Collection Platform (DCP) at the gaging station will be monitored to provide USGS early warning of high flows and the ability to sample during storm events.
- Discrete streamflow measurements will be made at all three sites every 6-8 weeks.
- Collected about every 6 to 8 weeks at each site.
- Collected during high flow events and during the period of spring snowmelt to characterize suspended–sediment loading during flows carrying the greatest loads.
- Collected using EDI protocols.
- An automatic sampler has been installed at the gaging station and will sample for suspended sediment during high flow events.
- Collected upon observation of bed sediment movement.
- Initial samples of bed sediment will be collected and analyzed at the Test America Laboratories for total petroleum hydrocarbons (TPH). Data from these bed sediment samples will be used to evaluate past presence or absence of TPH in Clear Creek.
- Aqueous concentrations of TPH will be evaluated by quarterly deployment of three 15x16 cm semi–permeable membrane devices (SPMDs) over a period of a full year.
Water Chemistry Samples
Water chemistry samples are analyzed for major ions, trace elements, nutrients, DO, pH, specific conductance, and alkalinity.
- Collected on a quarterly basis approximately coinciding with fall, winter, spring, and summer seasons.
- Collected three times during spring runoff and up to four times within a given year during selected storm events.
- Major constituents include calcium, chloride, magnesium, potassium, sodium, and sulfate; trace constituents include, but are not limited to, arsenic, cadmium, chromium, nickel, uranium, and zinc.
- Nutrient samples will be analyzed for ammonium, nitrite, nitrate, total and dissolved organic nitrogen, orthophosphate, and total and dissolved phosphorus.
- Samples will be collected using equal–discharge–increment (EDI) protocols according to published USGS guidelines.
Data collected as part of this study will be evaluated in context with previously collected data. According to published information in Seiler and Wood (2009), data collected during and prior to 2007 preceded the development of a planned community and golf course near the center of the study area. Site 1, located at the terminus of the upstream segment, is intended to represent undeveloped conditions and there has been little to no development within this reach. Downstream from site 1, at sites 2 and 3, data collected from 2009 through 2012 were collected during the construction of the golf course and during the preparation of the land intended for the planned residential community. Samples collected as part of this effort will capture conditions in Clear Creek after the near completion of the golf course and during the construction of the residential area.
An additional Scientific Investigations Report will be released covering data collection for the period of 2013–16. The additional information on sediment yield and water quality in the Clear Creek watershed will assist in evaluating current and future changes in water chemistry and sediment transport in the watershed, which may be related to increased urbanization, wildfire, and implementation of best management practices.