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<br />~j <br />r,;) <br />';") <br />..-4 <br /> <br />~. ~l <br />o <br /> <br />MEASUREMENTS AND CALCULATIONS <br /> <br />The irrigation monitoring data being collected over the past several <br />years include; total irrigation inflow to the field, total surface <br />runoff (tailwater) leaving the field, total irrigation time for each <br />irrigation, number of hours irrigated per set, and average flow at <br />each furrow. Other data such as soi I moisture deficit (before and <br />after irrigation), deep percolation and depth infi Itrated are <br />calculated from the data collected in the field. In this report, all <br />data reported in inches of water is equivalent to acre inches of water <br />per acre. The data collected are explained below: <br /> <br />Volume of Inflow: The total volume of inflow to the field was measured <br />with electronic flow recorders at most sites or from flow meters <br />located at some sites. The inflows have been converted to an average <br />depth in inches over the entire field. <br /> <br />Volume of Outflow (runoff): The total volume of surface outflow from <br />the field was measured with electronic flow recorders and converted to <br />an average depth in inches over the entire field. For sites with <br />microspray or sideroll 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 gave 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 />reco rded manua II y at some of the mon i to red I ocat ions. <br /> <br />Potential Evapotranspiration (ETp): Potential evapotranspiration was <br />calculated using a Modified Penman equation developed by the ARS at <br />Fort Coil ins, Colorado. The measured data parameters included wind <br />run, solar radiation, maximum and minimum temperatures, relative <br />humidity, and precipitation. The calculated ETp results were <br />c~1 ibrated with ETp results gathered by the ARS on the Colorado State <br />University Experimental Farm in the Grand Valley. <br /> <br />Actual Evapotranspiration (ETa): Actual evapotranspiration was <br />calculated using the ETp, times a crop coefficient based on type of <br />crop and stage of development, and stress factor based on days since <br />precipitation or irrigation. The crop coefficient and stress <br />adjustments were suppl ied by the ARS in Grand Junction and Fort <br />Co II ins. <br /> <br />Soil Water Deficit (S.W.D.): The soi I water deficit was computed as <br />1) the measured pre-season S.W.D. plus ETa minus effective rainfal I <br /> <br />11 <br />