Nevada is the most arid state in the Nation, receiving as little as 3 inches of annual precipitation in some parts of the state, while total statewide annual precipitation measures less than 10 inches. Consequently, Nevada only has large streams but no large rivers and only a few large lakes. Water resources throughout the State are limited making data about streams and lakes extremely important.
How are streams measured?
The major streams in Nevada are measured using real-time streamgages and by hydrologic technicians. Streamgages sit beside a stream and use a device to automatically measure the water level of the stream at periodic intervals.The water level is then transmitted to USGS computers where it is converted to a streamflow (discharge) measurement by applying a rating curve to the water-level data. About every 6 weeks, hydrologic technicians visit each stream to measure the streamflow directly.
A more detailed explanation is available here: Making Streamflow Measurements
Current streamflow conditions for 169 sites in Nevada are available from the USGS National Water Information System web site: NWISweb.
Daily streamflow conditions are summarized each day and are stored in the NWIS database. Daily data are updated to the web once a day.
Once a year, data are finalized and published in the annual data report. The annual data report is available at http://wdr.water.usgs.gov/.
A terminal lake is a lake that has streams that flow into it but no streams that flow out of it. Nevada has two large terminal lakes, Walker and pyramid, as well as many small lakes that occur in the many valleys within the State.
Terminal lakes generally are formed when streams enter a basin surrounded by higher ridges; this allows the water to pool and form a lake. One major issue with terminal lakes is the amount of dissolved nutrients that get carried into the lake from streams. When the amount of water in the lake can not be sustained due to drought or upstream diversions, terminal lakes can be come very saline, or salty, which has a huge impact on aquatic life in the lake.