Naomi Nakagaki, Wesley W. Stone, Michael E. Wieczorek 201209 Version 1.0, June 12, 2012 raster digital data Sacramento, CA U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?ssurgo_srlag This dataset consists of four national 1-kilometer (km) resolution rasters of the estimated percent presence of the soil restrictive layer (SRL) in the upper 25, 35, 45, and 55 centimeters of agricultural land. These rasters were developed from selected criteria of soil parameters from the Soil Survey Geographical (SSURGO) database and mapped agricultural land from the National Land Cover Database 2001 (NLCD 2001), version 2. The SRL rasters are used to characterize drainage basins for stream sites sampled in the National Water-Quality Assessment (NAWQA) program. These rasters were originally developed to serve as potential explanatory variables in the Watersheds Regressions for Pesticides (WARP) model (Stone and Gilliom, 2009; Stone and others, 2008; Larson and others, 2004). Purpose References are found in the Supplemental_Information section. Purpose References: Stone, W.W. and Gilliom, R.J., 2009, Update of watershed regressions for pesticides (WARP) for predicting atrazine concentration in streams: U.S. Geological Survey Open-File Report 2009-1122, 22 p., accessed September 4, 2012, at http://pubs.usgs.gov/of/2009/1122/ Stone, W.W., Gilliom, R.J., and Crawford, C.G., 2008, Watershed regressions for pesticides (WARP) for predicting annual maximum and maximum moving-average concentrations of atrazine in streams: U.S. Geological Survey Open-File Report 08-1186, 19 p. accessed September 4, 2012, at http://pubs.usgs.gov/of/2008/1186/ Larson, S.J., Crawford, C.G., and Gilliom, R.J., 2004, Development and application of watershed regressions for pesticides (WARP) for estimating atrazine concentration distributions in streams: U.S. Geological Survey Water-Resources Investigations Report 03-4047, 68 p., accessed September 4, 2012, at http://pubs.usgs.gov/wri/wri034047/ The SSURGO tables that were used to create this dataset are: CHORIZON - Horizon table COMPONENT - Component table LEGEND - Legend table MAPUNIT - Mapunit table The fields extracted from one or more of these tables are: COKEY - a non-connotative string of characters used to uniquely identify a record in the Component table. MUKEY - a non-connotative string of characters used to uniquely identify a record in the Mapunit table. MAJCOMPFLAG - a flag that indicates whether or not a component is a major component in the mapunit. HZDEPT_r - the distance from the top of the soil to the upper boundary of the soil horizon (representative value). KSAT_r - the amount of water that would move vertically through a unit area of saturated soil in unit time under unit hydraulic gradient(representative value). COMPPCT_r - the percentage of the component of the mapunit (representative value). For a complete listing of the tables and columns in the SSURGO database, please refer to: http://soildatamart.nrcs.usda.gov/documents/SSURGO%20Metadata%20-%20Tables%20and%20Columns%20Report.pdf (accessed 9/4/12) For the descriptions of the SSURGO columns, please refer to: http://soildatamart.nrcs.usda.gov/documents/SSURGO%20Metadata%20-%20Table%20Column%20Descriptions%20Report.pdf (accessed 9/4/12). For information regarding the relationships in the SSURGO database, please refer to: http://soildatamart.nrcs.usda.gov/documents/SSURGO%20Metadata%20-%20Relationships%20Report.pdf (accessed 9/4/12). 201109 acquisition date of the SSURGO database Complete None planned -127.86 -65.27 48.23 22.88 none inlandWaters National Water Quality Assessment Program NAWQA Watershed Regressions for Pesticides (model) WARP Soil Survey Geographic Database SSURGO soil restrictive layer SRL agricultural land none conterminous United States none See "Distribution_Liability" section. Acknowledgment of the U.S. Geological Survey would be appreciated. Naomi Nakagaki U.S. Geological Survey Geographer mailing address

CSUS Campus

Placer Hall

6000 J Street

Sacramento CA 95819 USA 916 278 3092 916 278 3070 nakagaki@usgs.gov 8:00am-4:30pm WST Please contact thru email http://water.usgs.gov/GIS/browse/ssurgo_srlag25.jpg Map of the soil restrictive layer in the upper 25 centimeters of agricultural land JPEG http://water.usgs.gov/GIS/browse/ssurgo_srlag35.jpg Map of the soil restrictive layer in the upper 35 centimeters of agricultural land JPEG http://water.usgs.gov/GIS/browse/ssurgo_srlag45.jpg Map of the soil restrictive layer in the upper 45 centimeters of agricultural land JPEG http://water.usgs.gov/GIS/browse/ssurgo_srlag55.jpg Map of the soil restrictive layer in the upper 55 centimeters of agricultural land JPEG Not applicable for raster data. none to report U.S. Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) 201109 raster digital data Fort Worth, TX NRCS 12,000 - 63,630 external hard drive 200310 200410 publication date of printed soil survey SSURGO Geospatial data of soil map units by MUKEY; tabular data of the following SSURGO variables: HZDEPT_R, KSAT_R, COKEY, MAJCOMPFLAG, and MUKEY. These variables are from the CHORIZON, COMPONENT, LEGEND, and MAPUNIT tables - all used to compute weighted averages of the soil restrictive layer. U.S. Geological Survey 201102 raster digital data 30 meters online, downloaded from http://www.mrlc.gov/nlcd01_data.php, in February 2011 1999 2004 ground condition NLCD 2001v2 mapped areas of agricultural land (classifications "Cultivated crops" and "Pasture/hay" - codes 82 and 81, respectively) Please refer to the Supplemental_Information section for the descriptions of the SSURGO columns (fields) and tables that are identified below. The SSURGO tabular data were used to compile estimates of SRL by: 1. Requesting all SSURGO county data files from Rosemary Riveria (Natural Resources Conservation Service, Fort Worth, TX) on 08/31/2011. An external hard drive containing these data was received on or about 09/10/2011. Therefore, the SSURGO data are current as of September 2011. 2. Combining the individual county-level CHORIZON, COMPONENT, LEGEND, and MAPUNIT tables so that there was only one file for each of CHORIZON, COMPONENT, LEGEND, and MAPUNIT tables. These files were all converted to RDB files (Relational DataBase files, which are formatted as tab-delimited text) for processing. 3. Analyzing the CHORIZON table to determine the presence of a Soil Restrictive Layer (SRL) as follows: 3a. SRL25: For HZDEPT_r < 25cm, if KSAT_r <= 1.25, then SRL present 3b. SRL35: For HZDEPT_r < 35cm, if KSAT_r <= 1.25, then SRL present 3c. SRL45: For HZDEPT_r < 45cm, if KSAT_r <= 1.25, then SRL present 3d. SRL55: For HZDEPT_r < 55cm, if KSAT_r <= 1.25, then SRL present 4. Joining the results of the analysis for the CHORIZON table with the COMPONENT table through the COKEY field. If a SRL was present in a COMPONENT then all of that COMPONENT was considered to have a SRL. (Each COMPONENT represents a certain percentage of the MAPUNIT, which is quantified in the COMPONENT COMPPCT_r field). 5. Evaluating the joined CHORIZON and COMPONENT tables to determine the percent SRL in the MAPUNIT (via the MUKEY linking field) as follows: 5a. Retaining and using only COMPONENT records with "majcompflag" equal to "Yes", 5b. Determining the percent presence of a SRL in a MAPUNIT by taking the weighted average of the COMPONENTS making up that MAPUNIT. The COMPPCT_r percentages were used to weight the average percent presence of the SRL in the MAPUNIT. The result of steps 1-5 was a table of MAPUNITS (identified by MUKEY) and associated SRL25, SRL35, SRL45, and SRL55 percents. MAPUNITs with no data were left blank and MAPUNITs with zero percent SRL25, SRL35, SRL45, or SRL55 were preserved as a zero value. 201111 The original SSURGO map unit polygons were gridded at the 10-m resolution, then resampled to 30-m resolution. 201111 The tabular data of SRL variables and the 30-m resolution grid of soil map unit were combined to create a national SRL grid by map unit for each of the 4 depths. 201111 A national grid of agricultural land was compiled from the National Land Cover Database 2001, version 2 by extracting the 30-m grid cells classified as either "Cultivated crops" and "Pasture/hay". 201206 The national grid of agricultural land was overlain with each SRL grid by map unit to produce a 30-m resolution SRL grid of agricultural land for each of the soil layers, the upper 25, 35, 45, and 55 centimeters. 201206 An interim 1-km resolution grid of SRL 25, 35, 45, and 55 on agricultural land was generated by resampling the output grid from the previous step from 30-m to 40-m resolution. The intent was to resample to a cell size that factors evenly into 1,000. Because resampling to the 25-m resolution would create a raster dataset that contained more detail than that captured in the original data, the resampling took place at the 40-m resolution. Simultaneously, the mean of the 40-m grid cells within each 1-by-1-km grid cell was determined and the output grid contained the mean value for each 1-by-1-km grid cell. The "aggregate" function accomplished the computations described in this step. 201206 Below is the programming code used (in the ArcWorkstation environment) to create the SRL raster for the upper 25 centimeters of agricultural land. The SRL rasters for the upper 35,45, and 55 centimeters were processed in the same manner. /* SRL25_us30 = 30-m resolution grid of SRL25 estimates, mapped /* by soil map unit /* nlcd01ag_all = 30-m resolution grid of agricultural land /* co2001g1km = 1-km resolution grid of 2001 county boundaries /* grid setcell 30 setwindow SRL25_us30 SRL25_us30 /* 1. Create a SRL25 grid on just agland /* set the mask grid to the nlcd01 ag cells, 30m setmask nlcd01ag_all SRL25_ag30m = con (nlcd01ag_all gt 0,SRL25_us30,0) /* 2. Resample to 40m and cr8 1km grid of means setcell 40 setwindow SRL25_ag30m nlcd01ag_all SRL25agt = aggregate (SRL25_ag30m,25,mean) /* 3. Create final grid - divide by 100 (because SRL values were /* multiplied by 100) and set the mask to the extent of the /* 2001 county grid so that the shoreline/US boundary defines /* the outer boundary of the SRL grid setcell 1000 setmask co2001g1km srl25ag = srl25agt / 100 201206 Raster Grid Cell 2903 4618 1 Albers Conical Equal Area 29.500000 45.500000 -96.000000 23.000000 0.000000 0.000000 row and column 30.000000 30.000000 meters North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 The grid cell values in the rasters represent the percent presence of the soil restrictive layer in the upper 25,35,45, and 55 centimeters of agricultural land. The grid cell values range from 0 to 100. There is no value attribute table for the raster because the data values are stored as floating numbers. The only attribute table associated with the raster are the "statistics" files, "srl25ag.sta", "srl35ag.sta", "srl45ag.sta", and "srl55ag.sta". These files contain the following statistics for the grid cells in the raster: 1) minimum value (MIN); 2) maximum value (MAX); 3) mean value (MEAN), and 4) standard deviation (STDV). These statistics were internally computed by the GIS software. none U.S. Geological Survey Ask USGS - Water Webserver Team mailing

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Reston VA 20192 USA 1-888-275-8747 (1-888-ASK-USGS) http://water.usgs.gov/user_feedback_form.html Downloadable data Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of these data, software, or related materials. The use of firm, trade, or brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. The names mentioned in this document may be trademarks or registered trademarks of their respective trademark owners. Raster Four ArcInfo grids in a single workspace zip 29 MB http://water.usgs.gov/GIS/dsdl/ssurgo_srlag_grd.zip ASCII Four ASCII rasters in a single folder zip 30 MB http://water.usgs.gov/GIS/dsdl/ssurgo_srlag_asc.zip None. This dataset is provided by USGS as a public service. 201209 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing

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Reston VA 20192 USA 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+ssurgo_srlag FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998