Laserfiche WebLink
a monthly soil moisture budget, inclusion of water supply, and the ability to consider effective <br />precipitation buildup in the soil profile. <br />In addition to these enhancements, procedures are being added for calculating consumptive use for <br />agriculture categories such as stock pond evaporation and livestock uses as well as ?other categories.? <br />Other categories include municipal, industrial, reservoir evaporation, and basin exports. In the past, the <br />consumptive use calculations for these categories were not automated. Also, the CRDSS CU model will <br />include a calibration factor to increase the accuracy of the model for local conditions. <br />Soil Moisture Budget <br />The current implementation of the SCS Blaney-Criddle CRDSS CU method will maximize the beneficial <br />contribution of stored soil moisture from effective precipitation and winter buildup. The CRDSS CU <br />model estimates irrigation water requirement, which is the depth of irrigation water required <br />consumptively for crop production, exclusive of effective precipitation and carry over soil moisture. The <br />carry over soil moisture is the accumulated soil moisture from previous months. Each month will begin <br />at or above the management allowed depletion (MAD). The MAD varies with each crop, each month, <br />and according to soil texture. <br />This method of interpreting the soil moisture budget could result in three situations: <br />1.If the first month's irrigation water requirement (IWR) is below the MAD level the farm head <br />gate requirement (FHR) is raised by the amount needed to start the next month at the MAD <br />level. <br />2.If stored soil moisture from the first month or over the winter plus the effective precipitation <br />exceeds crop evapotranspiration needs, the additional water will be stored in the soil profile up <br />to the field's moisture-holding capacity and will carry over to the next month. <br />3.If IWR is equal to MAD, the soil moisture budget will begin at the MAD level for the next <br />month. <br />Effective Precipitation <br />Monthly and seasonal effective precipitation can be expected to vary widely from year to year. Like <br />XCONS2, the methodology presented in TR-21 will be an option as well as an additional USBR method. <br />The first method is the SCS method as described in TR-21, where the calculated effective precipitation is <br />a function of the irrigated application depth, total precipitation and monthly consumptive use. The <br />second method is the USBR method, where the effective precipitation is a function of total monthly <br />precipitation. <br />Water Supply <br />Naturally, unless water is available from precipitation, ground water, or irrigation there cannot be <br />consumptive use from crops. In areas of the arid and semi-arid west, such as the Western Slope of <br />Colorado, the major source of water is irrigation. In these areas, the quantity and seasonal distribution of <br />the available water supply (irrigation) will affect the consumptive use characteristics of agricultural <br />lands. <br />2 <br />A275 01.09.95 1.14-14 CSU IDS <br />