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Data Assessment <br />Snow information is primarily used during the forecasting process and during the melt period. <br />Historical data might be evaluated in context of recorded decisions and in evaluation of <br />improvements to the runoff forecast and curtailment decision making processes. Additional data <br />may be beneficial in helping develop more reliable streamflow estimates. Additional snow data <br />collection is considered in developing the alternatives. <br />3.8 Irrigated Acreage <br />Irrigated acreage, essential to estimating consumptive use at a specific site or throughout the <br />basin, is potentially available from several sources. Irrigated acreage fluctuates over time, due to <br />crop prices, government support programs, and water supply, and is currently documented <br />annually by the Rio Grande Water Conservation District (RGWCD), as well as by the Farm <br />Service Agency for part of the valley. <br />Knowledge of crop type is essential for estimating consumptive use at a specific location. <br />However, crop statistics published by Colorado are only reported by county. These data have <br />been used as the basis for evapotranspiration estimates in a planning-scale model of the San Luis <br />Valley developed by the State. <br />Data Assessment: <br />The RGWCD has tabulated and mapped irrigated acreage and crop types within the District <br />annually on the north side of the Rio Grande since 1983, and on the south side since 1994. Data <br />are in an Excel spreadsheet by quarter. The spreadsheet identifies location, area, and crop type. <br />RGWCD data appear to be quality controlled and have been verified on the ground. The <br />RGWCD mapping does not cover mountain areas, the San Luis Valley north of the La Garita <br />Road, or any of Costilla County. <br />The State Engineer's Office reports irrigated acreage by ditch system, often with diversion <br />records. However, these data may have limited value for use in consumptive use estimates <br />because they are individually supplied and are not field verified. Additionally, data are only <br />available for those parcels that have been irrigated by surface supplies. The State Engineer's <br />Office has no irrigated acreage records for those parcels irrigated by wells. Where these data do <br />exist, no field verification has been done and no crop types are recorded. <br />The Farm Service Agency flies over the valley annually to photograph irrigated acreage for <br />compliance with farm programs; photographs were printed at large size for 1989 through 1991, <br />and acreage was digitized. Coverage is complete, but may not have been ground truthed. <br />Mapping does not currently reflect diversion structures or wells that irrigate these lands. The <br />Farm Service Agency data quality is unknown and may likely be outdated. The Farm Service <br />Agency photography does not cover upland and mountain areas (upper Rio Grande and possibly <br />upper Saguache Creek). <br />During the late 1980s, irrigated acreage data was compiled in preparation for the State's case in <br />the American Water Development, Inc. trial. The information is in an ASCII file, with one record <br />per quarter. It shows if the quarter is irrigated; if irrigation is by surface water, and if so, by what <br />ditch; and if a well exists on the quarter. Information from this source does not tell whether or not <br />corners are irrigated. The tabulation was developed from water commissioner's maps. The water <br />commissioner's maps seem to be regarded highly, although quality may vary from one district to <br />another. The ASCII data file does not cover upland and mountain areas (upper Rio Grande and <br />possibly upper Saguache Creek). <br />a454/report/fmaUdata. doc 7/2&~OS 3 -1 1 <br />