This data set represents the estimated percentage of the 1-km grid cell that is covered by or subject to the agricultural conservation practice (CPIS05), Combination of Irrigation Sources (CIS) on agricultural land by county (nri_is05)

This data set represents the estimated percentage of the 1-km grid cell that is covered by or subject to the agricultural conservation practice (CPIS05), Combination of Irrigation Sources (CIS) on agricultural land by county. A combination of irrigation sources means one or more sources of irrigation, such as wells, ponds, or streams are used on agricultural land. (U.S. Department of Agriculture, 1995) This data set was created with geographic information systems (GIS) and database management tools. The acres on which CIS's are applied were totaled at the county level in the tabular NRI database and then apportioned to a raster coverage of agricultural land within the county based on the Enhanced National Land Cover Dataset (NLCDe) 1-kilometer resolution land cover grids (Nakagaki, 2003). Federal land is not considered in this analysis because NRI does not record information on those lands.

本数据集用于估算各县农用地范围内，被农业保护措施CPIS05（灌溉水源组合，Combination of Irrigation Sources，CIS）覆盖或纳入其适用范围的1公里网格单元占比。所谓灌溉水源组合，指在农用地上使用一种或多种灌溉水源（如水井、池塘或溪流）。（美国农业部，1995年）
本数据集依托地理信息系统（Geographic Information Systems，GIS）与数据库管理工具构建完成。实施灌溉水源组合的农田面积已在表格化国家资源清单（National Resources Inventory，NRI）数据库中按县级单位汇总，随后基于增强型国家土地覆盖数据集（Enhanced National Land Cover Dataset，NLCDe）的1公里分辨率土地覆盖网格（中垣直树，2003年），被分配至各县境内的农用地栅格图层中。本次分析未纳入联邦土地，因国家资源清单（NRI）未记录此类土地的相关信息。