Area- and Depth-Weighted Averages of Selected SSURGO Variables for the Conterminous United States and District of Columbia

This digital data release consists of seven national data files of area- and 
depth-weighted averages of select  soil attributes for every available county 
in the conterminous United States and the District of Columbia as of March 
2014. The files are derived from Natural Resources Conservations Service’s 
(NRCS) Soil Survey Geographic database (SSURGO). The data files can be 
linked to the raster datasets of soil mapping unit identifiers (MUKEY) available 
through the NRCS’s Gridded Soil Survey Geographic (gSSURGO) database 
(http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/geo/?cid=nrcs142p2_053628). 
			
The associated files, named DRAINAGECLASS, HYDRATING, HYDGRP, 
HYDRICCONDITION, LAYER, TEXT, and WTDEP are area- and depth-weighted 
average values for selected soil characteristics from the SSURGO database for 
the conterminous United States and the District of Columbia. The SSURGO 
tables were acquired from the NRCS on March 5, 2014. The soil characteristics 
in the DRAINAGE table are drainage class (DRNCLASS), which identifies the 
natural drainage conditions of the soil and refers to the frequency and duration 
of wet periods. The soil characteristics in the HYDRATING table are hydric rating 
(HYDRATE), a yes/no field that indicates whether or not a map unit component is 
classified as a "hydric soil". The soil characteristics in the HYDGRP table are the 
percentages for each hydrologic group per MUKEY. The soil characteristics in the 
HYDRICCONDITION table are hydric condition (HYDCON), which describes the 
natural condition of the soil component. The soil characteristics in the LAYER 
table are available water capacity (AVG_AWC), bulk density (AVG_BD), saturated 
hydraulic conductivity (AVG_KSAT), vertical saturated hydraulic conductivity 
(AVG_KV), soil erodibility factor (AVG_KFACT), porosity (AVG_POR), field 
capacity (AVG_FC), the soil fraction passing a number 4 sieve (AVG_NO4), the 
soil fraction passing a number 10 sieve (AVG_NO10), the soil fraction passing a 
number 200 sieve (AVG_NO200), and organic matter (AVG_OM). The soil 
characteristics in the TEXT table are percent sand, silt, and clay (AVG_SAND, 
AVG_SILT, and AVG_CLAY). The soil characteristics in the WTDEP table are 
the annual minimum water table depth (WTDEP_MIN), available water storage 
in the 0-25 cm soil horizon (AWS025), the minimum water table depth for the 
months April, May and June (WTDEPAMJ), the available water storage in the 
first 25 centimeters of the soil horizon (AWS25), the dominant drainage class 
(DRCLSD), the wettest drainage class (DRCLSWET), and the hydric classification 
(HYDCLASS), which is an indication of the proportion of the map unit, expressed 
as a class, that is "hydric", based on the hydric classification of a given MUKEY. 
(See Entity_Description for more detail). 
			
The tables were created with a set of arc macro language (aml) and awk (awk was 
created at Bell Labsin the 1970s and its name is derived from the first letters of the 
last names of its authors – Alfred Aho, Peter Weinberger, and Brian Kernighan) scripts. 
Send an email to mewieczo@usgs.gov to obtain copies of the computer code 
(See Process_Description.) 
The methods used are outlined in NRCS's "SSURGO Data Packaging and Use" (NRCS, 2011). 
			
The tables can be related or joined to the gSSURGO rasters of MUKEYs by the item 
'MUKEY.' Joining or relating the tables to a MUKEY grid allows the creation of grids 
of area- and depth-weighted soil characteristics. A 90-meter raster of MUKEYs is 
provided which can be used to produce rasters of soil attributes.  More detailed 
resolution rasters are available through NRCS via the link above.

Tags: alaska, annual-minimum-water-table-depth, available-water-storage-in-the-first-25-centimeters-of-the-soil-horizon, average-water-capacity, bulk-density, dominant-drainage-class, drainage-class, environment, geoscientific-information, geoscientificinformation, hawaii, hydric-condition, hydric-rating, hydrologic-groups, inlandwaters, kfact, ksat, minimum-water-table-depth-for-the-months-april-may-and-june, organic-material, percent-clay, percent-sand, percent-silt, porosity, puerto-rico, saturated-hydraulic-conductivity, soil-erodibility-factor, soils, ssurgo, united-states, usgs-2321a431-f98e-45e5-b136-f026ea3a90dd, vertical-saturated-hydraulic-conductivity, wettest-drainage-class
Organization: Department of the Interior