This 2004 Reporting Cycle, 305(b) Report for Nevada assesses water quality data based on the last two years since the previous 305(b) Report. The number of data points for the assessed reaches varied from one data points to twelve data points. Some assessments used best professional judgment when no data was available. This report represents a general overall assessment of the Waters of the State and is not intended to indicate impaired waters which relate to 303(d) listing.

The State of Nevada operates an extensive monitoring program which encompasses the States 110,567 acres, regularly monitoring over 100 sampling points in the 14 hydrographic regions found in the state. In addition to these fixed monitoring stations, several water quality intensive field studies are conducted on the major water systems of Nevada. These studies included Truckee River, Carson River, Walker River and the Humboldt River. In addition a number of lakes and reservoirs have been added to the monitoring program.

There are approximately 14,988 miles of perennial rivers and streams, 126,257 miles of intermittent/ephemeral streams and channels, 1,782 miles of ditches/canals and 551 border miles of shared rivers. Nevada has 1,070 lakes, reservoirs or ponds with an approximate total acreage of 533,239 (these river and lake sizes are according to EPA's "Total Waters Report") and approximately 136,650 acres of wetlands.

This 305(b) report addresses a total of 3,002.70 stream miles and 1,359.53 river miles in Nevada. The overall use support of the streams are 2,360.60 miles fully supporting, 456.63 miles are partially supporting and 185.47 miles are non supporting. The overall use support of the rivers are 280.44 miles fully supporting, 304.45 miles are partially supporting and 774.64 miles are non supporting. The remaining river/stream miles are not assessed because of their inaccessibility due to there remote location and that the majority of these streams are ephemeral and intermittent.

Of the lakes and reservoirs addressed in this report 148,660.19 acres of reservoirs are included in this report. 141,660.19 acres are fully supporting, 4,393.00 acres are partially supporting and 2,695.54 acres are non supporting. 187,101.00 acres of lakes are included in this report. 151,611.00 acres are fully supporting and 35,490.00 acres are non supporting. 197,477.81 acres were not assessed in this report due to lack of data or information.

There are 136,650 acres of freshwater wetlands of which 51,826 acres are included in this report. 38,826 acres are fully supporting all assessed uses, 13,000 acres are non supporting for one or more uses while 84,824 acres were not assessed in this report due to lack of data or information.

Beneficial uses are assigned to classified waters in Nevada but not all waters have the same uses applied to it. These beneficial uses include aquatic life, wildlife propagation, recreation involving water contact, recreation not involving water contact, municipal drinking supply, stock watering, irrigation and industrial supply.

Since Nevada is a water poor state, the water which is available is under great demand and is heavily used. The major users are agriculture and municipal and industrial sources. The impacts on water quality from the municipal and industrial sources has been greatly reduced over the years with most point source polluters eliminated from direct discharges or are stringently controlled. Agriculture has the greatest impacts on the waters of Nevada due mainly to nonpoint source pollution along with naturally occurring causes. Some causes are directly related to irrigation, grazing and flow regulation practices. The reduction in flows in many of the rivers account for much of the non support of beneficial uses. Temperature, pH, DO, nutrients and suspended solids are the main pollutants of concern and are being targeted in the Nonpoint Source Program.

Water quality has generally been improving due to the removal of point sources and more stringent standard being implemented on the remaining point sources. Most exceedances are seasonal and are of a natural condition.

The Nonpoint source program will help to further improve water quality by promoting public awareness, grazing and irrigation practices, erosion control measures and implementation of Best Management Practices.

The Carson River water quality standard for total phosphates was exceeded. Temperature, Turbidity and Suspended Solids exceedances generally occur during the summer months at low flows. The major causes can be attributed to nonpoint sources in Carson Valley, a major agricultural area and growing urban area. Drought conditions followed by sever flooding is felt to be the major contributing factor to water quality problems in the river. A fish consumption health advisory has been issued for portions of the Lower Carson River and Lahontan Reservoir since 1985 due to high levels of mercury. Portions of the river are a designated EPA Superfund Site.

The Walker River has seen improvement in pH, nitrates and phosphates during this reporting cycle. Temperature continues to be a problem in the system and TDS continues to be a problem for the lower reach including Walker Lake.

The Humboldt River showed improvements to water quality with turbidity continuing to be a problem during this reporting cycle. The river normally has a highly variable flow with a major irrigation / recreation reservoir on the lower end of the system (Rye Patch Reservoir) and a terminal sink. Major point sources have all but been eliminated.

Agricultural and rangeland nonpoint sources are contributing the large sediment and nutrient loads to the waters of the State. Urban drainage systems contribute nutrients, heavy metals and organic loads to the nonpoint source load. The Nonpoint Source Program which is being implemented should achieve reductions of these nonpoint source loads.

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