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<br />,~ <br />C'") <br />M <br />c) <br /> <br />. <br /> <br />. <br /> <br />first 3 irrigations to accurately record the inflow volume, the later <br />irrigation recordings were accurate. Of the 19 operational irrigation <br />sites, 2 of them had microspray systems, 3 had siderol I sprinkler <br />systems and 14 had surface i rr i gat i on systems <Tab I e 2). At each site <br />with a surface irrigation system, automated electronic flow recorders <br />were installed to measure the volume of inflow and outflow. At each <br />inflow and outflow site, these flow recorders were connected to <br />electronic data recorders. The flow recorders measured inflow and <br />outflow every 30 minutes and the measured flow data was recorded and <br />stored in the data recorders. <br /> <br />At sites with siderol I sprinkler or microspray irrigation systems, the <br />volume of inflow was obtained from automatic flow meters located on <br />the sites. There is no surface runoff and the volume of outflow was <br />therefore not measured. For these sites, outflow values were <br />considered to be evaporation losses <Table 2). <br /> <br />During the irrigation season, each site was serviced and maintained <br />approximately every 2 to 3 days. Equipment was cal ibrated and checked <br />every day when the sites were being irrigated. <br /> <br />The climatic parameters for calculations of ET data were transmitted <br />directly to the Grand Junction field office every 15 to 20 minutes <br />from the 2 weather stations located in the Grand Valley. These data <br />were stored in the computer for I ater use. <br /> <br />MEASUREMENTS AND CALCULATIONS <br /> <br />Volume of Inflow: The total volume of inflow to the field is measured <br />with electronic flow recorders at most sites or obtained from flow <br />meters located at some sites. The inflows have been converted to an <br />average depth In inches over the entire field. <br /> <br />Volume of Outflow (runoff): The total volume of surface outflow from <br />the field is measured with electronic flow recorders and converted to <br />an average depth in inches over the entire field. For sites with <br />microspray or siderol I sprinkler systems, outflow values were <br />considered to be evaporation losses; 10% and 20% respectively of <br />inflow volume. <br /> <br />Infiltrated Depth: The infiltrated depth, in inches equals the inflow <br />minus the outflow. This IS the average amount of water entering the <br />soi lover the entire field. <br /> <br />Precipitation: The precipitation was electronically measured and <br />recorded at the two weather stations. On-site precipitation was also <br />recorded manually at some of the monitored locations. <br /> <br />Potential Evapotranspiration (ETp): Potential evapotranspiration was <br />calculated using a modified Penman equation developed by the ARS In <br /> <br />6 <br />