Michael Wieczorek, USGS Unpublished Material Version 1.1, February 19, 2002 raster digital data Baltimore, MD U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?ofr041189607 This data set represents the estimated percentage of the 1-km grid cell that is covered by or subject to the agricultural conservation practice (CP607), Surface Drainage, Field Ditches (SDFD) on agricultural land by county. Surface Drainage, Field Ditches are described as "a graded ditch for collecting excess water." (U.S. Department of Agriculture, 1995) This data set was created with geographic information systems (GIS) and database management tools. The acres on which SDFD'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. This dataset was created for two main purposes; (1) summarize and provide refined spatial detail to attributes of agricultural practices from the 1992 NRI dataset; and (2) to support hydrologic modeling. The U. S. Geological Survey's (USGS) National Water-Quality Assessment (NAWQA) program is using the spatially refined SDFD dataset to produce ancillary information for characterizing surface and ground-water sampling sites. Calculation of percentages of NAWQA study areas treated by Surface Drainage, Field Ditches is one example of the type of use of this data set. The 1992 NRI data was used because it was created in the same early to mid-1990s time frame as the NLCD. NAWQA plans on processing the NRI in this fashion every 5 years as new NRI and NLCDE data are published. The U.S. Geological Survey (USGS) initiated the National Water-Quality Assessment (NAWQA) Program in 1991 to accomplish two primary objectives. The first objective was to assess the status and trends in the quality of the Nation's ground-water and surface-water resources, and the second objective was to link the status and trends with an understanding of the natural and human factors that affect water quality (Gilliom and others, 1995). "The National Resources Inventory is a statistically based sample of land-use and natural resource conditions and trends on U.S. nonfederal lands. It is the most comprehensive database of its kind ever attempted anywhere in the world. The Natural Resources Conservation Service's program for NRI serves as the Federal Government's principal source of information on the status, condition, and trends of soil, water, and related resources in the United States. The assessment of a nation's natural resources and environmental condition provided by the NRI requires a nationally consistent database that allows for manipulation of various parameters in order to make accurate assessments. For these manipulations and subsequent analyses to be useful for public policy considerations, the NRI database has a high degree of reliability, looks at the natural resources over a period of time, and permits analyses at national, regional, and local levels. The NRI is unique because it provides a nationally consistent database for all nonfederal lands, it features data gathered and monitored in 1982, 1987, 1992, and 1997 by thousands of technical and natural resource data collection experts, and it has a direct correlation with soils data, which permits analysis of resources in relation to the capability of the land and in terms of soil resources and conditions. Informed and valid decisions are best made when based upon scientifically derived data. The NRI has been developed to supply this type of information. The NRI database is powerful, credible, and scientifically constructed. The present NRI is the result of many decades of development." (U.S. Department of Agriculture, 1995) Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the dataset in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology. Cited references Gilliom, R.G., Alley, W.M., and Gurtz, M.E., 1995, Design of the National Water-Quality Assessment Program--occurrence and distribution of water-quality conditions: U.S. Geological Survey Circular 1112, 33 p. U.S. Department of Agriculture. May 1995 (Reissued). 1992 National Resources Inventory, Natural Resources Conservation Service, Washington, DC, and Statistical Laboratory, Iowa State University, Ames, Iowa, CD-ROM. 1992 unknown ground condition Complete As needed -127.887748 -65.346810 51.608770 22.860749 none Surface Drainage, Field Ditches Agricultural Practices National Resources Inventory inlandWaters none Conterminous United States 1992 None The NRI dataset is tabulated at the county level only and deemed accurate for this analysis (Nusser and Goebel, 1997). The spatial distribution of this data also assumes the NLCDe has an acceptable accuracy for this analysis (Nakagaki, 2003). Therefore this data set does not provide specific locations of a particular NRI code but the percent of county agricultural land that practices NRI code 607 over the total agricultural land in a particular county. Michael Wieczorek U.S. Geological Survey Geographer mailing and physical address

8987 Yellow Brick Road

Baltimore MD 21237 USA (410) 238-4250 (410) 238-4210 mewieczo@usgs.gov Prepared as part of the National Water-Quality Assessment Program. Kerie J. Hitt, USGS, supplied the 1992 NRI database and Naomi Nakagaki, USGS, supplied an updated version of the National Land Cover Dataset processed at 1-kilometer resolution. Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 1; ESRI ArcCatalog 9.0.0.535 Nusser, S. M., and J. J. Goebel, 1997, The National Resources Inventory: A Long-Term Multi-Resource Monitoring Programme, Environmental and Ecological Statistics, 4(3):181- 204. PCT Represents the percentage of a cell of agricultural land which Surface Drainage, Field Ditches (SDFD) are practiced. Environmental Systems Research Institute, Inc. (ESRI) ARC 8.3 software was used to test the data for consistency against the original NRI tabular data, 12/04/03. Several NRI codes in random counties were selected in both the derived GIS dataset and the original tabular file. The total sum of area was compared and found to be the same. Naomi Nakagaki 200311 Unknown Version 2, November 2003 map Sacramento, CA USA U.S. Geological Survey ftp://ftpdcascr.wr.usgs.gov/nsp/natsyngis/NLCDe1km.tgz online 1992 ground condition NLCDE VALUE (land cover code) U.S. Department of Agriculture 19950101 Unknown tabular digital data Fort Worth, TX SCS National Cartography & GIS Center U.S. Department of Agriculture, May 1995 (Reissued). 1992 National Resources Inventory, Natural Resources Conservation Service, Washington, DC, and Statistical Laboratory, Iowa State University, Ames, Iowa, CD-ROM. http://gis.esri.com/library/userconf/proc95/to200/p1682.html CD-ROM Unknown Unknown NRI PCT is percentage of cell that is Agricultural land treated with CPIS01 conservation practice.