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2.0 INTRODUCTION <br />The RGDS S Irrigated Lands Assessment was performed for the State of Colorado as part of the Rio <br />Grande Decision Support System. The goal of the RGDSS Irrigated Lands Assessment was to <br />determine the extent (i.e. irrigated parcel boundary and ditch service area) and character (i.e. crop <br />type) of irrigated lands in the valley floor of the Rio Grande Basin during the 1998 irrigation season. <br />The character (i.e. land cover class) ofnon-irrigated lands within the ground water model area was <br />also determined. <br />Figure 1 shows the location of the Rio Grande Basin within the state of Colorado. It also highlights <br />the ground water model area located on the San Luis Valley floor where the majority of the irrigated <br />lands assessment was focused. This information will be used in other tasks to estimate consumptive <br />uses in the Basin and will also be integrated into the RGDSS spatial database. <br />Four GIS products were developed as part of the RGDSS irrigated lands assessment: <br />1) a ditch service area theme was produced to delineate the service area boundaries of the <br />surface water structures in the basin, <br />2) a composite false color satellite image was developed to serve as a raster backdrop to other <br />GIS themes, <br />3) an irrigated parcel theme was developed to delineate the boundary and important attributes <br />of the irrigated parcels within the basin, <br />4) a land cover classification theme (delineating irrigated and non-irrigated land types) was <br />developed to assist in determining the consumptive use of the non-irrigated portions of the <br />basin. <br />Satellite imagery, interviews, and existing data sources were used to create the irrigated lands <br />products. Figure 2 is a diagram that shows how data flows and eventually results in the four major <br />products. In the data flow diagram, diagonal boxes indicate data sources, rectangular boxes <br />represent processing steps, and the chamfered boxes represent the four irrigated lands assessment <br />products. The development of these four products will be discussed in more detail in the following <br />sections. <br />This report describes how the irrigated lands inventory was derived from satellite imagery and <br />vector data. The executive summary of the report summarizes the conclusions of this study. The <br />following section provides descriptions of the approach taken, including data acquisition, data <br />processing and results. The results section presents summaries of the final products. <br />4 <br />