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The Amargosa River is an approximately 300-kilometer long regional drainage connecting the northern highlands on the Nevada Test Site in Nye County, Nev., to the floor of Death Valley in Inyo County, Calif. Streamflow analysis indicates that the Amargosa Desert portion of the river is dry more than 98 percent of the time. Infiltration losses during ephemeral flows of the Amargosa River and Fortymile Wash provide the main sources of ground-water recharge on the desert-basin floor. The primary use of ground water is for irrigated agriculture. The current study examined ground-water recharge from ephemeral flows in the Amargosa River by using streamflow data and environmental tracers. The USGS streamflow-gaging station at Beatty, Nev., provided high-frequency data on base flow and storm runoff entering the basin during water years 1998–2001. Discharge into the basin during the four-year period totaled 3.03 million cubic meters, three quarters of which was base flow. Streambed temperature anomalies indicated the distribution of ephemeral flows and infiltration losses within the basin. Major storms that produced regional flow during the four-year period occurred in February 1998, during a strong El Niño that more than doubled annual precipitation, and in July 1999. The study also quantified recharge beneath undisturbed native vegetation and irrigation return flow beneath irrigated fields. Vertical profiles of water potential and environmental tracers in the unsaturated zone provided estimates of recharge beneath the river channel (0.04–0.09 meter per year) and irrigated fields (0.1–0.5 meter per year). Chloride mass-balance estimates indicate that 12–15 percent of channel infiltration becomes ground-water recharge, together with 9–22 percent of infiltrated irrigation. Profiles of potential and chloride beneath the dominant desert-shrub vegetation suggest that ground-water recharge has been negligible throughout most of the basin since at least the early Holocene. Surface-based electrical-resistivity imaging provided areal extension of borehole information from sampled profiles. These images indicate narrowly focused recharge beneath the Amargosa River channel, flanked by large tracts of recharge-free basin floor.

Floods are among the most frequent and costly natural disasters in terms of human hardship and economic loss. In July 1992, for example, flooding of several drainages near Hawthorne, Nevada, caused road closures and damage to homes and businesses (Hughes, 1992). In the 1960's, the U.S. Geological Survey (USGS) recognized the need for reliable quantitative information to predict magnitudes and frequencies of flooding, and initiated a nationwide investigative program of monitoring peak discharges. As part of this program, the USGS, in cooperation with the Nevada Department of Transportation (NDOT), designed and implemented a stream-gaging network. In Nevada, the network consists of crest-stage gages and miscellaneous sites. A crest-stage gage is a permanent device that registers the peak stage of streamflow at a site during the time interval between inspections. Peak-discharge data primarily were derived at these gage sites through indirect (after-the-flood) measurements using the slopearea method (Dalrymple and Benson, 1976). However, most drainages are not monitored using a gage due to the dominantly ephemeral and uncertain character of streamflow throughout the State. Peak-discharge data also were determined at these ungaged miscellaneous sites using the slope-area method. The statewide network has nearly 4 decades of peak-discharge measurements. These data are reviewed for notable hydrologic characteristics and trends. For example, the Wassuk Range, a discrete geographical area, has experienced several severe floods. This fact sheet presents select data and information pertaining to these floods.

Rapid spilling of 22 acre-feet of water down the steep, 3-mile channel of Ophir Creek killed one, injured four, and destroyed or damaged five houses. Flow evolved into debris flow enroute, and compounded in volume over 30 times.

Aquifers near Fallon, Nev., all belong to a large interdependent system that can be subdivided into four subsystems on the basisof hydrologic characteristics.Listed in decreasing order of present use, they are: A hydraulically complex, shallow, unconsolidated sedimentary aquifer containing water of variable chemical character; a highly permeable deeper basalt aquifer containing nearly chemically homogeneous, moderately fresh water; an intermediate-depth, unconsolidated sedimentary aquifer locally containing large quantities of freshwater; and a deep, generally unconsolidated, sedimentary aquifer that probably contains mostly .salinewater. Electrical-resistivity data suggest that the deeply buried basalt aquifer is generally mushroom shaped; characteristically, much of it overlies the deep sedimentary aquifer and underlies the intermediate aquifer.It is recharged mainly by freshwater from the intermediate aquifer and apparently contains a blend of freshwater and saline water, the freshwater having the dominant proportion.Water from the basalt aquifer in areas of large withdrawals contains chemical evidence of modern (post-1953) recharge from surface sources.Pre-pumpage basalt recharge is supplemented by pumpage-induced recharge proportionate to annual pumpage rates.The basalt aquifer is highly transmissive and exhibits a nearly flat potentiometric surface.The shallow sedimentary aquifer is inherently susceptible to pollution and contains mainly hard water.The salinity of the shallow ground water is influenced by irrigation-water recharge.Known reserves of freshwater in the intermediate alluvial aquifer are expanding with exploration activity.Water from all aquifers contains greater than normal concentrations of dissolved arsenic.-"-

The five principal creeks, First Creek, Second Creek, Wood Creek, Third Creek, and Incline Creek, with a cumulative drainage of 17.8 square miles, furnished a yearly average of about 15,000 acre-feet of runoff, mainly snowmelt, to Lake Tahoe during the 1970-73 water years. Annual runoff from the individual streams ranged from 460 to 7,070 acre-feet, and discharges ranged from 0.2 to 110 cubic feet per second. During the 4 years, the five streams delivered 31,000 tons of sediment, which averaged about 75 percent gravel and sand, 15 percent silt, and 10 percent clay, to the lake. Annual quantities ranged from 1,500 to 11,000 tons; individual streams furnished 20 to 5,200 tons annually. Measured sediment transport at the stream mouths ranged from 1 to 13,200 milligrams per liter and from 0.001 to 1,420 tons per day; sediment concentrations up to 63,200 milligrams per liter were measured at upstream tributary sites. Estimated annual sediment yields of principal drainage basins ranged from 3 to 930 tons per square mile from undeveloped areas and from 26 to 5,000 tons per square mile from developed areas; yields for developed areas appeared to average about 10 times those of undeveloped areas, and roadways apparently were the major source. Erosion disequilibrium caused by prestudy flash floods on two creeks continues to manifest itself through high natural sediment yields. The Second Creek flood of 1967 yielded about 75,000 tons in one afternoon. Fluvial nutrient transport seems quantitatively related to magnitudes of sediment and water transport. Movement rates of organic nitrogen and particulate phosphorus were greater than rates of other nutrient species moving to the lake.

Heavy thunderstorm precipitation on the afternoon of July 3, 1975, between metropolitan Las Vegas and the mountains to the south, west, and north, caused flash flooding in the city area. Total storm precipitation equaled or exceeded 3 inches (76 mm) in some areas. The total storm yield on the area of significant runoff was probably between 20,000 and 25,000 acre-feet (2.5 x 107 m3 and 3.1 x 107 m3) of water. Of this amount, probably less than 3,000 acre-feet (37 x 106 m3) flowed directly to Lake Mead. Peak flows of Tropicana Wash, Flamingo Wash, Las Vegas Creek, and Las Vegas Wash were the highest ever determined. Flooding caused the loss of two lives and inflicted extensive property damage. Total damage was reportedly estimated by the Clark County Flood Control District at $4-5 million. Problems associated with sediment erosion, transportation, and deposition occurred throughout the flooded area. An unknown amount of the material transported during the flood was deposited in Lake Mead near the mouth of Las Vegas Wash. Lateral erosion appeared more prominent than vertical erosion along most major channels, except on Las Vegas Wash at Northshore Road where downcutting threatened the loss of the highway. Sediment deposits were particularly noticeable and troublesome in Flamingo Wash at Caesars Palace parking lot and on the Winterwood Golf Course near the junction of Flamingo Wash and Las Vegas Wash.

A devastating flash flood of thunderstorm origin struck Eldorado Canyon, a 22.9-square-mile drainage with a history of flooding, in southern Nevada, at about 2:30p.m., September 14, 1974.The flood killed at least 9 people, destroyed 5 trailer homes and damaged many others, obliterated a restaurant, destroyed 38 vehicles, 19 boat trailers, 23 boats, half of the boat-docking facilities, and the gas dock.The severe runoff resulted from intense basinwide rain and hail at rates up to 3 inches of precipitation per half an hour.The storm moved down basin and generally increased in intensity, which compounded runoff rates.Peak discharge was estimated to be 76,000 cubic feet per second just upstream from the developed area near the canyon mouth.About 2,000 acre-ft of runoff reached Lake Mohave, the canyon terminus.Runoff dumped an estimated 70,000 cubic yards (about 100,000 tons) of inorganic sediment in Lake Mohave and throughout the lowermost canyon reach.It also delivered an estimated 4 acre-ft of organic or floating debris to Lake Mohave.The inorganic sediment was estimated to be less than 1 percent boulders, 40 to 60 percent gravel, 20 to 40 percent sand, and 10 to 25 percent silt-clay.Although the recurrence interval for this magnitude runoff is great, a similar flood could occur in any given year.These types of flash floods , although common in the desert southwest, are not fully understood and are frequently ignored, and therefore the danger to developed areas is not decreased.With proper understanding and informed planning, the risk of damage from similar floods in the future can be greatly reduced.