Snowmelt-driven streamflow in the mountain watersheds of western North America is the primary water source for urban, agricultural, natural ecosystems, and hydropower generation throughout the region. The

Heated water was cooled rapidly to impact temperatures that produce optimum growth in plants by applying the water with a standard irrigation sprinkler. Maximum cooling was observed nearest the sprinkler, where the smallest droplets were measured, and temperatures and mean diameters generally increased with distance from the source. Impact temperatures of the water droplets approached but did not reach wet bulb temperatures. Water as hot as 50øC was cooled to droplet temperatures of 25øC or less when the sprinklers were operated in an associated arid climate and at line pressures greater than 25 psi. A theoretical treatment correlated well with one selected set of experimental data and with predicted cooling rates for specified droplets in several typical atmospheric conditions and one untypical condition for an arid climate. Only under the condition of high relative humidity at a given ambient temperature does it appear that cooling might be insufficient to produce usable sprinkler water from 50øC supply water for crop production. IATTRODUCTIOl•Large quantities of heated water from steampowered electric generators and other industries are added to water systems of the biosphere [Cadwallader, 1964]. Increased water temperatures are generally undesirable, and they impair the biological quality of aquatic systems [Odum, 1959]. Alternatives to direct return of heated water would benefit the quality of rivers or lakes used for such industrial purposes. One such alternative is to use this water for irrigating agricultural fields.Relatively little work has been done to identify the potential effects of using warmed water for crop irrigation IRahey and Mihara, 1967]. Schultz [1964], Hilgeman e• al. [1964], Wheaton [1964], and Pogrell and Kidder [1960] reported beneficial effects of water in frost• protection. Soil warming by early spring watering was shown to stimulate early plant growth [Bodine, 1917; Ehrler and Bernstein, 1958]. Hot water treatment to control soil organisms has also been reported [Baker, 1962; Maggenti, 1962; Langridge, 1963]. Plant tolerance to temperature varies with species, but in most crop plants yields decline at root temperatures of about 30øC and death occurs when temperatures rise above 38 ø [Mil-let, 1938]. Friend et al. [1962a, 1962b, 1964] studied temperature response in wheat and found that 30øC gave the optimum growth rate but that over the entire growth period the relative growth rate was greatest at 25øC. Thus, where source water exceeds tolerable temperatures, some means of cooling will be required to assure successful usage for crop growth.This study was undertaken to measure the extent of temperature reduction attainable by use of a standard sprinkler and to identify the role of specific environmental and operating factors in affecting the rate of cooling. METI-IODS ,• Experimental. A standard irrigation sprinkler (Rainbird •p35) with a 3•9-mm-diameter nOZZle was placed in a pipe riser at a height of I meter above the ground. Water temperatures and pressures were measured with appro...

The 2085 km 2 Jordan River Basin, and its seven sub-catchments draining the Central Wasatch Range immediately east of Salt Lake City, UT, are home to an array of hydrologic, atmospheric, climatic and chemical research infrastructure that collectively forms the Wasatch Environmental Observatory (WEO). WEO is geographically nested within a wildland to urban land-use gradient and built upon a strong foundation of over a century of discharge and climate records. A 2200 m gradient in elevation results in variable precipitation, temperature and vegetation patterns. Soil and subsurface structure reflect systematic variation in geology from granitic, intrusive to mixed sedimentary clastic across headwater catchments, all draining to the alluvial or colluvial sediments of the former Lake Bonneville. Winter snowfall and spring snowmelt control annual hydroclimate, rapid population growth dominates geographic change in lower elevations and urban gas and particle emissions contribute to episodes of severe air pollution in this closed-basin. Long-term hydroclimate observations across this diverse landscape provide the foundation for an expanding network of infrastructure in both montane and urban landscapes. Current infrastructure supports both basic and applied research in atmospheric chemistry, biogeochemistry, climate, ecology, hydrology, meteorology, resource management and urban redesign that is augmented through strong partnerships with cooperating agencies. These features allow WEO to serve as a unique natural laboratory for addressing research questions facing seasonally snow-covered, semi-arid regions in a rapidly changing world and an excellent facility for providing student education and research training.

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The Jordan River Basin, and its seven sub-catchments of the Central Wasatch Mountains immediately east of Salt Lake City, UT, are home to an array of research infrastructrure that collectively form the Wasatch Environmental Observatory (WEO). Each sub-catchment is comprised of a wildland to urban land use gradient that spans an elevation range of over 2000 m in a linear distance of˜25km. Geology varies across the sub-catchments, ranging from granitic, intrusive to mixed sedimentary rocks in uplands that drain to the alluvial or colluvial sediments of the former Lake Bonneville. Vegetation varies by elevation, aspect, distance to stream channels, and land use. The sharp elevation gradient results in a range of precipitation from 700 to 1200 mm/yr (roughly 2/3 as snow) and mean annual temperature from 3.5 o to 6.8 o C. Spring snowmelt dominates annual discharge. Although climate is relatively similar across the catchments, annual water yield varies spatially by more than a factor of 3, ranging from 0.18 to 0.63. With historical strengths in ecohydrology, water supply, and social-ecological research, current infrastructure supports both basic and applied research in meteorology, climate, atmospheric chemistry, hydrology, ecology, biogeochemistry, resource management, sustainable systems, and urban redesign. Climate and discharge data span over a century for the seven sub-catchments of the larger basin. These data sets, combined with multiple decades of hydrochemistry, isotopes, ecological data sets, social survey data sets, and high-resolution LiDAR topography and vegetation structure, provide a baseline for long-term data collected by NEON, public agencies, and individual research projects. The combination of long-term data with active state of the art observing facilities allows WEO to serve as a unique natural laboratory for addressing research questions facing rapidly growing, seasonally snow-covered, semi-arid regions worldwide and an excellent facility for providing student education and research training.