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In T~ible 10, loamy sand and sand are combined. The parameter values that are shown in the table are for loamy sand. XKSAT for sand is often used as 4.6 inches/hour, and PSIF is often used as 1.9 inches. Using those parameters values for drainage areas can result in the qeneration of no rainfall excess which may or may not be correct. Incorrect results coulci cause serious consequences for flood control planning and design. Therefore, it is recommended that for watersheds consisting of relatively small sub-areas of sand, the Green and Ampt parameter vafues for loamy sand be used for the sand portion of the watershed. If the area contains a large portion of sand, either the Green and Ampt method should be used with the parameter values for loamy sand or the Initial Loss and Uniform Loss Rate method should be used with the appropriately determined values for the para meters. New research relating soil texture with XKSAT has recently been published (Sax~:on and Rawls, 2004). This information has not been evaluated and tested to determine its application for hydrologic modeling, but may be of value in the future. The methods presented herein can be accomplished using hand computation techniques including hard copy maps and use of a planimeter or other suitable method for estimating the ~~reas of irregular polygons. More complex watersheds with detailed soils mapping including numerous polygons defining multiple soil textures may, from a practical stancipoint, require analysis using CADD or GIS software. These guidelines are based on the following presumptions, but the user should note that the quidelines herein can also be accomplished following the same basic procedures using hand computations or CADD software. 1. ESRI ArcMap GIS software will be used to facilitate the computations. The guidelines presented herein provide an outline level of guidance that can be implemented at various levels of detail using GIS. These guidelines can be applied using standard GIS software, but there are third-party software programs such as WMS, DDMSW and various CADD software packages that will also perform many of the computation steps documented herein, except for determining a controlling soil texture for each soil map unit present in a given study area. 2. The user has a base map in GIS format or a hard-copy map for the study area of interest with the drainage area delineated into sub-basins. 19 March 2007 34