<URL:http://water.usgs.gov/nawqa-only/gw.html>
This data set consists of area weighting factors for STATSGO (State Soil Geographic) mapping units for NAWQA LUS and SUS areas. The weighting factors can be used to calculate average soil statistics for data compiled for STATSGO soil mapping units.
This is one of the ancillary GIS data layers developed to characterize NAWQA ground water studies for national synthesis of water-quality data.
<URL:http://water.usgs.gov/lookup/getmeta?muid>
The soils mapping unit weighting factors were created by overlaying each ground water study area with the STATSGO soils geographic mapping units (MUIDs). 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 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 (from STATSGO data) 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.
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 AREAID. Missing data is indicated by -9999. An example of using the weighting factors to calculate average PERMAVE for a ground water study area is shown under Process_Step.
Fields in the soils weighting table are:
SUID NAWQA study unit SUCODE NAWQA study unit/network code 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