STATSGO soil characteristics (soil hydrologic group, slope, water table depth, depth to bedrock, permeability, available water capacity, bulk density, organic matter content, soil erodibility factor, soil erodibility factor for uppermost horizon, soil loss tolerance, wind erodibility group, soil texture, shrink-swell potential, permeability of least permeable layer, vertical permeability, hydric soils, soil drainage class, and soil order) for ground water study areas (Land Use Studies and Subunit Surveys)
<URL:http://water.usgs.gov/nawqa-only/gw.html>
This data set consists of STATSGO (State Soil Geographic) data on soil hydrologic group, slope, water table depth, depth to bedrock, permeability, available water capacity, bulk density, organic matter content, soil erodibility factor, soil erodibility factor for uppermost horizon, soil loss tolerance, wind erodibility group, soil texture, shrink-swell potential, permeability of least permeable layer, vertical permeability, hydric soils, soil drainage class, and soil order for NAWQA ground water study areas (Land Use Studies and Subunit Surveys). The soils geographic areas and soils characteristics are from the 1994 STATSGO data base. Average soil characteristics were prepared by David Wolock using methods described in Wolock (1997). DRAIN was prepared by Schwarz and Alexander (1995).
This is one of the ancillary GIS data layers developed to characterize NAWQA ground water studies for national synthesis of water-quality data.
The STATSGO input data set did not include Alaska and Hawaii.
In the national coverage of soils polygons, each soil polygon is identified by a map unit identifier (MUID). The MUID is the smallest physical delineation of soil components. The MUID may contain up to 21 soil components and each component may contain up to 6 layers. Although the components are not delineated in the spatial data base, the attribute data base does have the area of each component within a map unit. The area is expressed as the percentage of the map unit and is called the component percent.
David Wolock compiled the soils attribute data from STATSGO and computed a weighted average for each characteristic (except texture, drain, and vertical permeability) for each MUID using methods similar to those in Wolock (1997). Wolock used similar but unpublished methods for computing a weighted average for texture. Some of the attributes are not available for all of the MUIDs. A missing characteristic is indicated by a flag called GOTDAT in the input data. GOTDAT equals one when data values are present.
Weighted averages were computed for these attributes in the LAYER table:
PERML--- low value for permeability (inches per hour) PERMH--- high value for permeability (inches per hour) AWCL---- low value for available water capacity (fraction) AWCH---- high value for available water capacity (fraction) BDL----- low value for bulk density (grams per cubic centimeter) BDH----- high value for bulk density (grams per cubic centimeter) OML----- low value for organic matter content (percent by weight) OMH----- high value for organic matter content (percent by weight). COMPPER indicates the percentage of components in the average value.Soil characteristics from the LAYER table -- permeability (PERM), available water capacity (AWC), bulk density (BD), and organic matter (OM) -- were aggregated by soil layer and component using these assumptions: 1) Only soil components with ROCKDEPH (soil thickness) greater than 0 are used. 2) Only soil layers with BDL greater than 0 and AWCL greater than 0 and PERML greater than 0 and depth to the lower boundary of the soil layer (LAYDEPH) greater than 0 are used. OML can include 0 values. This means that the averages only include land surface areas with soils that can be a medium through which water can flow. Rock outcrops, for example, are excluded. 3) Not all soil components in the COMP table have associated values in the LAYER table. Also, some components are rock outcrops and water, or they can be missing data. These components are not included in the MUID average, and therefore the item COMPPER can be less than 100 percent.
Here is an example:
MUID OML OMH COMPPER GOTDAT FL129 0.065 0.422 96.000 1 FL132 0.428 1.255 95.000 1Weighted averages were computed for these attributes in the COMP table:
SLOPEL--- Low value for land surface slope (percent) SLOPEH--- High value for land surface slope (percent) WTDEPL--- Low value for depth to the seasonally high water table (feet) WTDEPH--- High value for depth to the seasonally high water table (feet) ROCKDEPL- Low value for the total soil thickness examined (inches) ROCKDEPH- High value for the total soil thickness examined (inches). COMPPER indicates the percentage of components in the average value.Soil characteristics from the COMP table -- slope (SLOPE), depth to seasonally high water table (WTDEP), and total soils thickness (ROCKDEP) -- were aggregated by soil component using these assumptions: 1) Only soil components with ROCKDEPH greater than 0 are used. 2) ROCKDEPL and ROCKDEPH measure the total thickness examined, which is usually 60 inches. If the value is less than 60 inches, then the value indicates the depth to bedrock. 3) Some components are rock outcrops and water, or they can be missing data. These components are not included in the MUID average, and therefore the item COMPPER can be less than 100 percent.
Here is an example:
MUID SLOPEL SLOPEH COMPPER GOTDAT FL129 0.204 4.541 98.000 1 FL132 0.000 2.000 95.000 1For the attributes in the LAYER and COMP tables listed above, the weighted average high and low values were averaged ([HIGH + LOW] / 2) to come up with one value (a midpoint) to represent each soil characteristic in each MUID. For example:
MUID OML OMH OMAVE COMPPER GOTDAT FL129 0.065 0.422 0.244 96.000 1 FL132 0.428 1.255 0.842 95.000 1 MUID SLOPEL SLOPEH SLOPEAVE COMPPER GOTDAT FL129 0.204 4.541 2.373 98.000 1 FL132 0.000 2.000 1.000 95.000 1Weighted averages also were computed for these attributes in the LAYER table:
KFACT--- soil erodibility factor TFACT--- soil loss tolerance factor WEG----- wind erodibility. COMPPER indicates the percentage of components in the average value.KFACT is the soil erodibility factor which is adjusted for rock fragments. This erodibility factor can be used to predict the long-term average soils loss. It is a quantitative value that is experimentally determined. The representative classes are .02, .05, .10, .15, .17, .20, .24, .28, .32, .37, .43, .49, .55 and .64.
KFACT_UP is the soil erodibility factor for the uppermost soil horizon.
TFACT is the soil loss tolerance factor. It represents the maximum rate of soil erosion that will permit a high level of crop production. The classes of TFACT's are 1, 2, 3, 4, 5.
WEG is the wind erodibility group assigned to the soil layer or horizon. Soils that have similar properties affecting their resistance to soil blowing in cultivated areas are grouped together. The groups indicate the susceptibility to blowing. The classes of WEG's are 1, 2, 3, 4, 4L, 5, 6, 7, and 8, and are explained in more detail in the STATSGO data use publication.
Weighted averages were computed for KFACT by aggregating by soil layer and component using these assumptions: 1) Only soil components with ROCKDEPH (high value for the total soil thickness examined, in inches) greater than 0 are used. 2) Only soil layers with KFACT greater than 0 and LAYDEPH (depth to the lower boundary of the soil layer) greater than 0 are used. 3) Not all soil components in the COMP table have associated values in the LAYER table. Also, some components are rock outcrops and water, or they can be missing data. These components are not included in the MUID average, and therefore the item COMPPER can be less than 100 percent.
Weighted averages were computed for TFACT by aggregating by soil layer and component using these assumptions: 1) Only soil components with ROCKDEPH greater than 0 are used. 2) Only soil layers with TFACT greater than 0 and LAYDEPH greater than 0 are used. 3) Not all soil components in the COMP table have associated values in the LAYER table. Also, some components are rock outcrops and water, or they can be missing data. These components are not included in the muid average, and therefore the item COMPPER can be less than 100 percent.
Weighted averages were computed for WEG by aggregating by soil layer and component using these assumptions: 1) Only soil components with ROCKDEPH greater than 0 are used. 2) Only soil layers with WEG greater than 0 and LAYDEPH greater than 0 are used. 3) Not all soil components in the COMP table have associated values in the LAYER table. Also, some components are rock outcrops and water, or they can be missing data. These components are not included in the muid average, and therefore the item COMPPER can be less than 100 percent. 4) WEG class 4L was reclassified as class 4.
We did not calculate a midpoint for KFACT, TFACT, or WEG.
Weighted averages were computed for these attributes in the LAYER table that describe soil TEXTURE:
CLAYL --- low value for clay content, expressed as a percentage
of the material less than 2 mm in size.
CLAYH --- high value for clay content, expressed as a percentage
of the material less than 2 mm in size.
NO4L----- low value of percent by weight of soil material less
than 3 inches in size and passing a No. 4 sieve (5 mm).
NO4H----- high value of percent by weight of soil material less
than 3 inches in size and passing a No. 4 sieve.
NO10L---- low value of percent by weight of soil material less
than 3 inches in size and passing a No. 10 sieve (2 mm).
NO10H---- high value of percent by weight of soil material less
than 3 inches in size and passing a No. 10 sieve.
NO200L--- low value of percent by weight of soil material less
than 3 inches in size and passing a No. 200 sieve (.074 mm).
NO200H--- high value of percent by weight of soil material less
than 3 inches in size and passing a No. 200 sieve.
COMPPER indicates the percentage of components in the average value.
Weighted averages were computed by aggregating by soil layer and
component using these assumptions: 1) Only soil components with
ROCKDEPH (high value for the total soil thickness examined, in
inches) greater than 0 are used. 2) Only soil layers with
LAYDEPH (depth to the lower boundary of the soil layer) greater
than 0 are used. 3) No missing values for any of the soil
attributes (CLAYL, CLAYH, NO4L, NO4H, N0200L, NO200H, NO10L,
NO10H) were allowed. 4) No percentage texture value greater than
100 was allowed. 5) Not all soil components in the COMP table
have associated values in the LAYER table. Also, some components
are rock outcrops and water, or they can be missing data. These
components are not included in the MUID average, and therefore
the item COMPPER can be less than 100 percent.
Here is an example for CLAYL:
MUID CLAYL CLAYH COMPPER GOTDAT FL129 1.014 5.320 96.000 1 FL132 1.390 6.469 95.000 1The weighted average high and low values were averaged ([HIGH + LOW] / 2) to come up with one value (a midpoint) to represent each soil characteristic in each MUID:
CLAYAVE = (CLAYL + CLAYH) / 2 NO4AVE = (NO4L + NO4H) / 2 NO10AVE = (NO10L + NO10H) / 2 NO200AVE = (NO200L + NO200H) / 2For example:
MUID CLAYL CLAYH CLAYAVE COMPPER GOTDAT FL129 1.014 5.320 3.167 96.000 1 FL132 1.390 6.469 3.930 95.000 1Soil texture is based on the relative proportions of sand, silt, and clay in the fraction of soil that is less than 2 mm in size. Several methods of defining particle size classes exist. We use a combination of the USDA (U.S. Department of Agriculture) and the Unified method. Here are the definitions of sand, silt, and clay that are used here:
GRAIN SIZE (MM) SIEVE NUMBER METHOD
SAND 2.00 - 0.074 10 - 200 USDA/UNIFIED
SILT 0.074 - .002 200 - CLAY UNIFIED/USDA
CLAY Less than 0.002 CLAY USDA
Here is another way of describing our definitions:
SIEVE No. 10 No. 200
SIZE | | | | |
| GRAVEL | SAND | SILT | CLAY |
SIZE | | | | |
IN 2 .074 .002
MM
The "sand" and "silt" fractions represent a blend of methods.
The "sand" definition uses the USDA cutoff for sand/gravel (2
mm) and the Unified cutoff for sand/silt (0.074 mm). The range
excludes part of the "very fine sand" (.05 - .074 mm) fraction
from the USDA particle size scale. The "silt" definition uses
the Unified cutoff for sand/silt (0.074 mm) and the USDA cutoff
for silt/clay (.002 mm), and the range includes part of the
"very fine sand" (.05 - .074 mm) fraction from the USDA particle
size scale (Sharon Waltman, verbal commun., 1997).
For a diagram of the particle size classes see <URL:http://water.usgs.gov/nawqa-only/gwgis91/partsiz.jpg>, which is from the National Soil Survey Handbook (NRCS, 2003), available at <URL:http://soils.usda.gov/technical/handbook/>.
The description of soil texture is based on CLAYAVE, SILTAVE, and SANDAVE. The CLAYAVE value gives the percentage of clay directly. SANDAVE and SILTAVE must be derived using CLAYAVE and the values for the No. 10 and No. 200 sieve numbers. However, the sieve values are based on the portion of the soil that is less than 3 inches in size, and texture is based on the portion that is less than 2 mm in size. Therefore, each sieve value must be adjusted to represent the percentage of the soil fraction that is less than 2 mm. The adjustment is made by dividing each sieve value by the No. 10 sieve value and multiplying by 100.
NO10AVE adjusted = NO10AVE / NO10AVE * 100 NO200AVE adjusted = NO200AVE / NO10AVE * 100Then SANDAVE and SILTAVE (as a percent of the less than 2 mm fraction) can be estimated as:
SANDAVE = NO10AVE adjusted - NO200AVE adjusted
= NO10AVE / NO10AVE * 100 - NO200AVE / NO10AVE * 100
= 100 - NO200AVE / NO10AVE * 100
SILTAVE = NO200AVE adjusted - CLAYAVE
= NO200AVE / NO10AVE * 100 - CLAYAVE
The sum of CLAYAVE, SILTAVE, and SANDAVE is 100 percent.
The percent of each soil HYDROLOGIC GROUP was aggregated from the component percents comprising the particular group. For example,
MUID COMPONENT HYDGRP
PERCENT
FL132 45 B/D
FL132 5 D
FL132 15 B/D
FL132 10 B/D
FL132 5 D
FL132 5 B/D
FL132 5 D
FL132 5 D
FL132 5 D
In MUID FL132, the percentage of hydrologic group D is 25. The
percentage of hydrologic group B/D is 75.
The data set has two versions of HYDROLOGIC GROUP.
In the original STATSGO data, HYDROLOGIC GROUP information is missing for some of the soil components. For example, in MUID AR028, the sum of the component percents for HYDGRPs is only 78, which means that 22 percent of the components have missing data.
MUID COMPPCT HYDGRP AR028 7 A TOTAL COMPPCT A 7 AR028 10 B TOTAL COMPPCT B 10 AR028 22 C TOTAL COMPPCT C 31 AR028 2 C TOTAL COMPPCT D 30 AR028 6 C ---- AR028 1 C SUM OF COMPPCTs = 78 AR028 16 D AR028 1 D AR028 7 D AR028 1 D AR028 4 D AR028 1 DDave Wolock computed MUID hydrologic group percents based on the components that had data in the original STATSGO. For example, for MUID AR028, HYDGRP A is computed as 7 COMPPCT / 78 TOTAL COMPPCT, which results in 8.974 percent. The sum of all of the HYDGRP percents is 100 percent. The COMPPCT used to calculate the HYDGRP percents is 78 percent.
MUID =AR028 HGA = 8.974 HGB = 12.821 HGC = 39.744 HGD = 38.462 HGAD = 0.000 HGBD = 0.000 HGCD = 0.000 HGAC = 0.000 HGBC = 0.000 HGVAR = 0.000 COMPPERHG = 78.000Barb Ruddy and Bill Battaglin filled in missing HYDGRP for as many of the components as possible. For MUID AR028, they filled in 18 percent of the missing 22 percent of the COMPPCTs as HYDGRP D. This left 4 percent still missing.
TOTAL COMPPCT A 7
TOTAL COMPPCT B 10
TOTAL COMPPCT C 31
TOTAL COMPPCT D 48 (30 percent from raw STATSGO + 18 percent filled in as D)
----
SUM OF COMPPCTs = 96
Barb Ruddy computed MUID hydrologic group percents based on the
new set of components that had data. For example, for MUID
AR028, HYDGRP A is computed as 7 COMPPCT / 96 TOTAL COMPPCT,
which is 7.292 percent. The sum of all of Barb's HYDGRP
percents is 100 percent. The COMPPCT used to calculate the
HYDGRP percents is 96 percent.
MUID =AR028 HGABARB = 7.292 HGBBARB = 10.417 HGCBARB = 32.292 HGDBARB = 50.000 HGADBARB = 0.000 HGBDBARB = 0.000 HGCDBARB = 0.000 HGACBARB = 0.000 HGBCBARB = 0.000 HGVARBARB = 0.000 COMPPERBARB = 96.000SWELL is the shrink-swell potential (change in volume) upon drying and wetting.
PERGAVE is the vertical permeability and is not a simple weighted average (Freeze and Cherry, 1979). Rather it is calculated as:
PERGAVE = total depth of soil for given soil component
divided by
sum of (thickness of soil layer / permeability of soil layer)
for all soil layers
PERMIN is the permeability of the least permeable soils layer.
DEPMIN is the depth of the least permeable layer.
HYDRIC soils were indicated in the source data as Y (hydric) or N (not hydric). HYDRIC indicates the percent listed as Y (hydric).
For soil ORDER, only the three orders that make up most of the mapping unit percentage-wise are considered (highest three in terms of percentage of mapping unit). If Order A was in the highest 3, then ORDA is the percentage of Order A. If Order A is not in the highest three or does not occur at all, then ORDA is zero.
DRAINAGE CLASS data is from Schwarz and Alexander (1995). Drainage character is a two character code identifying the quality of the drainage for the component. The codes are E = excessive, SE = somewhat excessive, W = well drained, MW = moderately drained, SP = somewhat poorly drained, P = poorly drained, and VP = very poorly drained. These codes are converted into numeric values and assigned to the variable drain as follows: E = 1, SE = 2, W = 3, MW = 4, SP = 5, P = 6 and VP = 7.
Schwarz and Alexander construct a weighted average across all components of the component-specific information, the weights being the component percentages given for the map unit.
Note: The STATSGO data are compiled by generalizing more detailed county soil survey maps. (See SCS, 1994 for an explanation of how the STATSGO data were generated.) Because of their spatially generalized nature, the STATSGO data cannot be used to accurately estimate average soil characteristics for small areas. The STATSGO data use information document states that "STATSGO data are not detailed enough to make interpretations at a county level."
<URL:http://water.usgs.gov/lookup/getmeta?muid>
<URL:http://water.usgs.gov/lookup/getmeta?ussoils>
<URL:http://www.ncgc.nrcs.usda.gov/branch/ssb/products/statsgo/index.html>.
<URL:ftp://ftp-fc.sc.egov.usda.gov/NCGC/products/statsgo/statsgo-user-guide.pdf>.
<URL:http://soils.usda.gov/technical/handbook/>.
The average soils characteristics were determined for each study area by overlaying the ground water study area with the soils geographic mapping units (MUIDs) to create a set of soils mapping unit weighting factors. The weighting factors show all soil mapping units comprising the ground water study area and what fraction of the ground water study each MUID covers. The weighting factors then are used to compute weighted averages for the soils variables. This avoids doing multiple overlays of the study area and soils mapping units (i.e., avoids doing an overlay for each soil variable).
Here is an example of part of a soils weight table:
GW STUDY MUID AREAKM2 AREAF
ucollusrc1d_trg CO103 0.7 0.861 AREAF = AREAKM2/TOTAL AREAKM2
ucollusrc1d_trg CO111 0.1 0.072 for GW STUDY
ucollusrc1d_trg CO128 0.1 0.067
_______ _____
0.9 1.000 (AREAF should add to 1.)
MUID is the soil mapping unit. Three mapping units occur in the
ground water study.
AREAKM2 is the square kilometers of each mapping unit in the
ground water study.
AREAF is the fraction of the ground water study represented by each
mapping unit.
The values of permeability for each MUID are:
MUID PERMAVE CO103 8.000 CO111 4.822 CO128 0.541The weighted average of PERMAVE for ucollusrc1d_trg is calculated as
MUID CO103 MUID CO111 MUID CO128 TOTAL OF ALL
AREAF * PERMAVE AREAF * PERMAVE AREAF * PERMAVE AREAF's
MEAN-W-PERMAVE = (.861 * 8.000) + (.072 * 4.822) + (.067 * .541) / (.861 + .072 + .067) = 7.27
Processing routines are from the NAWQA area characterization
toolbox.
Added data for hydrologic groups modified by Barb Ruddy. See the Supplemental_Information section for an explanation.
with doughnuts without doughnuts cut out (correct) not cut out (incorrect) AREAID GRID AREA (M2) GRID AREA (M2) cnbrluscr1_bnd 7,044,202,800.000 7,392,941,100.000 cnbrluscr1_trg 5,706,866,700.000 6,766,256,700.000 connlusrc1_bnd 1,756,677,600.000 2,064,634,200.000 connlusrc1_trg 587,594,700.000 610,191,000.000 connsus2_bnd 6,848,918,100.000 7,617,282,300.000 nvbrlusrc1_trg 155,431,800.000 155,443,500.000 spltluscr2_trg 207,267,300.000 228,433,500.000
Also added studies that are resampled studies, but do not have the same boundaries in cycle 2 as were used in cycle 1:
albelusag1, nvbrsus2, trinsus3, sanjluscr1a, sanjlusor2a.
Also added willlusag3, which has the same boundaries as cycle 1 willlusag2.
The data set is referenced by SUCODE (NAWQA study unit/network code) and AREAID (ground water study boundary coverage). Two kinds of ground water network polygon coverages exist: 1) BND coverages, which represent the entire areal extent of the hydrogeologic unit defined for study, and 2) TRG coverages, which delineate the targeted land use within the BND.
The data set is organized by SUCODE and AREAID. Missing data is indicated by -9999. The soils data represent weighted averages for the study area.
The fields are:
SUID NAWQA study unit
SUCODE NAWQA study unit/network code
AREAID Ground water boundary coverage
HYDROLOGIC GROUP COMPUTED BY WOLOCK
USING ORIGINAL STATSGO DATA
(Some components had missing HYDGRP data.)
HGA soil hydrologic group A (percent)
HGB soil hydrologic group B (percent)
HGC soil hydrologic group C (percent)
HGD soil hydrologic group D (percent)
HGAD soil hydrologic group AD (percent)
HGBD soil hydrologic group BD (percent)
HGCD soil hydrologic group CD (percent)
HGAC soil hydrologic group AC (percent)
HGBC soil hydrologic group BC (percent)
HGVAR soil hydrologic group VAR (percent)
HYDROLOGIC GROUP COMPUTED BY RUDDY
USING MODIFIED STATSGO DATA
(Some missing HYDGRP data was assigned
a HYDGRP value.)
HGABARB soil hydrologic group A (percent)
HGBBARB soil hydrologic group B (percent)
HGCBARB soil hydrologic group C (percent)
HGDBARB soil hydrologic group D (percent)
HGADBARB soil hydrologic group AD (percent)
HGBDBARB soil hydrologic group BD (percent)
HGCDBARB soil hydrologic group CD (percent)
HGACBARB soil hydrologic group AC (percent)
HGBCBARB soil hydrologic group BC (percent)
HGVARBARB soil hydrologic group VAR (percent)
LAYER TABLE
SLOPEAVE average land surface slope (percent)
SLOPEL minimum value of land surface slope (percent)
SLOPEH maximum value of land surface slope (percent)
WTDEPAVE average depth to seasonally high water table (feet)
WTDEPL minimum value of depth to seasonally high water table (feet)
WTDEPH maximum value of depth to seasonally high water table (feet)
ROCKDEPAVE average total soil thickness examined (inches)
ROCKDEPL minimum value of total soil thickness examined (inches)
ROCKDEPH maximum value of total soil thickness examined (inches)
COMP TABLE
PERMAVE average permeability (inches per hour)
PERML minimum value of permeability (inches per hour)
PERMH maximum value of permeability (inches per hour)
AWCAVE average available water capacity (fraction)
AWCL minimum value of available water capacity (fraction)
AWCH maximum value of available water capacity (fraction)
BDAVE average bulk density (grams per cubic centimeter)
BDL minimum value of bulk density (grams per cubic centimeter)
BDH maximum value of bulk density (grams per cubic centimeter)
OMAVE average organic matter content (percent by weight)
OML minimum value of organic matter content (percent by weight)
OMH maximum value of organic matter content (percent by weight)
TEXTURE
CLAYAVE average clay content (percentage)
CLAYL minimum value of clay content (percentage)
CLAYH maximum value of clay content (percentage)
SILTAVE silt content (percentage)
SANDAVE sand content (percentage)
NO4AVE average percent by weight of soil material less
than 3 inches in size and passing a No. 4 sieve (5 mm)
NO4L minimum value of percent by weight of soil material less
than 3 inches in size and passing a No. 4 sieve (5 mm)
NO4H maximum value of percent by weight of soil material less
than 3 inches in size and passing a No. 4 sieve (5 mm)
NO200AVE average percent by weight of soil material less
than 3 inches in size and passing a No. 200 sieve (.074 mm)
NO200L minimum value of percent by weight of soil material less
than 3 inches in size and passing a No. 200 sieve (.074 mm)
NO200M maximum value of percent by weight of soil material less
than 3 inches in size and passing a No. 200 sieve (.074 mm)
NO10AVE average percent by weight of soil material less
than 3 inches in size and passing a No. 10 sieve (2 mm)
NO10L minimum value of percent by weight of soil material less
than 3 inches in size and passing a No. 10 sieve (2 mm)
NO10H maximum value of percent by weight of soil material less
than 3 inches in size and passing a No. 10 sieve (2 mm)
KFACT soil erodibility factor
KFACT_UP soil erodibility factor of uppermost soil horizon
TFACT soil loss tolerance factor
WEG wind erodibility
SWELL shrink-swell potential
PERGAVE vertical permeability (in/hr)
PERMIN permeability of the least permeable soils layer (in/hr)
DEPMIN depth of the least permeable layer
HYDRIC Percent in which hydric soils were identified (HYDRIC = Y)
DRAINAGE CLASS
DRAIN soil drainage class, converted to numeric value where
1 = E excessive
2 = SE somewhat excessive
3 = W well drained
4 = MW moderately drained
5 = SP somewhat poorly drained
6 = P poorly drained
7 = VP very poorly drained
ORDER
ORDA soil order A Alfisols (percent)
ORDC soil order C Andisols (percent)
ORDD soil order D Aridisols (percent)
ORDE soil order E Entisols (percent)
ORDH soil order H Histosols (percent)
ORDI soil order I Inceptisols (percent)
ORDM soil order M Mollisols (percent)
ORDO soil order O Oxisols (percent) - no occurrences
ORDS soil order S Spodosols (percent)
ORDU soil order U Ultisols (percent)
ORDV soil order V Vertisols (percent)
Fields in the soils weighting table are:
AREAID Ground water boundary coverage MUID100 Numeric representation of soils mapping unit id from 100 m soils grid AREAG Flag indicating area is within a ground water study (= 1) AREAKM2 Square kilometers of mapping unit in the ground water study AREAF Fraction of the ground water study represented by the MUID MUID10_KM2 Total area of soils mapping unit MUID10_F Fraction of soils mapping unit in the ground water study area (AREAKM2/MUID10_KM2) MUID Soils mapping unit id
kjhitt@usgs.gov
kjhitt@usgs.gov