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kaf/yr. <br />2.2.2 Consumptive Uses -Evapotranspiration (Et) in the valley was determined for irrigated crop <br />land, irrigated pastureland (incl. natural stream side vegetation), and for three classifications <br />of undeveloped land where the ground water table was 0-2 meters, 2-4 meters, and greater <br />than 4 meters below land surface. The total reported Et was 1,849 kaf/yr. Land <br />classifications were determined from interpretation of aerial photography. Potential Et for <br />irrigated crop land (29.3 in/yr), and pastureland (34.6 in/yr) were estimated using the <br />original Blaney-Griddle method. Undeveloped land Et was estimated using a modification <br />of the graph developed by Emery (1971) relating ground water depth to evapotranspiration <br />rates. The modification was to lower the Et for given water depths, such that the maximum <br />Et was 37.3 in/yr rather than 60 in/yr, as reported by Emery. <br />2.2.3 Change in Storage -Huntley states the average yearly change in storage is less than the <br />accuracy of measurement and can safely be ignored. His statement is based on findings by <br />Emery and others in 1973. <br />2.2.4 Outflows -Huntley estimates there are no surface water or ground water outflows from the <br />Closed Basin. <br />2.3 Water Budget Balance -Huntley, presents a balanced water budget, in other words inflows equal Et <br />since there are no surface or ground water outflows. <br />3.0 HRS Consultants, 1987 <br />3.1 Water Budget Area and Study Period -HRS Consultants conducted an average annual water budget <br />for the Alamosa Basin. The Alamosa Basin (Figure 1) is the San Luis Valley Floor area west and <br />north of the San Luis Hills. A consistent study period was not used since water budget components <br />were taken from various references such as surface water inflows from Emery with a 1924-69 study <br />period, and ground water inflows from Hearne and Dewey with a 1950-1980 study period. <br />3.2 Approach and Assumptions -The purpose of HRS's study was to define the potential development <br />of the confined aquifer. To show the relative contribution of inflow and outflow of ground water to <br />and from the deep confined aquifer of the Valley with respect to other inflow and outflow <br />components, a water budget for the Valley was constructed. The author of the water balance updated <br />the reported values in 1989 (Water in the Valley, A 1989 Perspective on Water Supplies, Issues, & <br />Solutions in the San Luis Valley, Colorado, Colorado Ground-Water Association, 1989). The <br />updated water budget values were used in this review. <br />3.2.1 Inflows - In this water budget, HRS inflows consist of surface water inflows, ground water <br />inflows, and precipitation. <br />Surface water inflows from the San Juan Mountains (1,260 kaf/yr) are based on the reported <br />values by Emery (1973). Ground water inflows (690 kaf/yr) were developed as result of <br />modeling by HRS. <br />Surface water inflows from the Sangre de Cristo Mountains are consistent with that reported <br />by Emery (1973) for the Alamosa Basin (215 kaf/yr). Ground water inflows from the <br />Sangre de Cristo Mountains (31 kaf/yr) are consistent with the Hearne and Dewey estimated <br />total inflow less the Emery estimated surface water inflows. <br />rg_task8-1_2001-08.doc 8 of 19 Apri16, 2001 <br />