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inches in May, 3.29 inches in June, and 4.21 inches in July were received. The monthly <br />precipitation amounts for these years are shown in Table 5-2 and Figure 5-1 following. <br />The timing of rainfall/precipitation dramatically influences the required irrigation. <br />Irrigators reported the late fall 2000 rainfall, winter 2000-2001 snow, and early spring <br />2001 moisture resulted in many wells being operated for only 1,500 hours during the <br />2001 growing season instead of the average of 2,000 hours. <br />Table 5-2. Comparison of Monthly Precipitation received at the Plainsman <br />Research Center, Walsh, Colorado. <br />Month <br />1999 <br />2000 <br />2001 <br />March <br />1.81 <br />3.55 <br />1.17 <br />April <br />3.73 <br />1.14 <br />0.56 <br />May <br />4.22 <br />0.72 <br />3.62 <br />June <br />0.56 <br />1.37 <br />3.29 <br />July <br />1.25 <br />3.17 <br />4.21 <br />August <br />3.75 <br />0.44 <br />2.18 <br />September <br />2.25 <br />0.15 <br />0.07 <br />October <br />3.70 <br />3.74 <br />0.14 <br />Total: <br />21.27 <br />14.28 <br />15.24 <br />From: Plainsman Research Center, Walsh, Colorado <br />5.3 ESTIMATED WATER USE <br />The ability to determine the amount of water actually being withdrawn from the aquifers <br />depends upon either direct measurement or approximation. Examples of direct <br />measurement include flow data obtained directly from wells that are either equipped with <br />totalizing flow meters or hour meters if the rate of discharge of the well is already known. <br />The approximation method utilizes equations and climatological data to estimate the <br />volume of water required. These two methods can be used together to provide accurate <br />estimates of the overall pumpage for an area. One method of estimating water demand <br />is based upon the Blaney-Criddle method with climatological input data from local sites. <br />In the Phase 1 report (MWE, 2001) water use was estimated for the four primary <br />irrigated crops in the District. The source of the crop coefficients used in the Blaney- <br />Criddle formula were from the "Irrigation Water Requirement Technical Release No. 21" <br />developed by the USDA's Soil Conservation Service. <br />V-2 <br />99-028.003\Phase 2 Report\ SHP Irrigated <br />