<URL:http://water.usgs.gov/nawqa-only/gw.html>
This data set consists of 1990 and 2000 population density and 1990 housing unit data (source of water, sewage disposal method, and median year built) for NAWQA ground water study areas (Land Use Studies and Subunit Surveys).
The population data sets are from the 1990 and 2000 Census of Population and Housing. The housing unit data is from the 1990 Census of Population and Housing STF3a. Kerie Hitt prepared the population density input values. Curtis Price extracted the housing unit data.
This is one of the ancillary GIS data layers developed to characterize NAWQA ground water studies for national synthesis of water-quality data.
Currently (May 28, 2004) the data set does not include AK or HI, but we have block group boundaries for those areas and plan to process the Census variables for these areas.
<URL:http://water.usgs.gov/nawqa-only/pop.html>
<URL:http://water.usgs.gov/nawqa-only/pop.html>
<URL:http://water.usgs.gov/nawqa-only/pop.html>
Ground water study boundaries are gridded at 30 meters and snapped to the NLCDE. Data processing occurs at 30 meters resolution.
Average Census characteristics were determined by overlaying the ground water study area with the 1990 and 2000 Census block group boundaries to create a set of block group weighting factors. The weighting factors show all block groups comprising the ground water study area and what fraction of the ground water study each block group covers. The weighting factors then are used to compute weighted averages for the Census variables. This avoids doing multiple overlays of the study area and block groups (i.e., avoids doing an overlay for each Census variable).
Here is an example of part of a block group weight table:
GW STUDY BGI 2000 AREAKM2 AREAF
ucollusrc1e_trg 080490002002 0.4 0.087 AREAF = AREAKM2/TOTAL AREAKM2
ucollusrc1e_trg 080490002004 4.3 0.913 for GW STUDY
______ _____
4.7 1.000 (AREAF should add to 1.)
BGI is the block group identifier. Two block groups occur in the
ground water study.
AREAKM2 is the square kilometers of each block group in the
ground water study.
AREAF is the fraction of the ground water study represented by each
block group.
The values of 2000 population density for each 2000 BGI are:
BGI POPDENS 080490002002 3.9 080490002004 7.6The weighted average of population for ucollusrc1e_trg is calculated as
BGI 080490002002 BGI 080490002004 TOTAL OF ALL
POPULATION AREAF * POP00 AREAF * POP00 AREAF's
DENSITY = (.087 * 3.9) + (.913 * 7.6) / (.087 + .913) = 7.2
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 SUCODE and AREAID.
The fields are:
SUID NAWQA study unit
SUCODE NAWQA study unit/network code
AREAID Ground water boundary coverage
POPULATION DENSITY
PDENS90 1990 population density (people/km2)
PDENS00 2000 population density (people/km2)
SOURCE OF WATER
WATPUBPV public system or private company (percent of housing units)
WATDRWEL individual well, drilled (percent of housing units)
WATDUWEL individual well, dug (percent of housing units)
WATOTH some other source of water (percent of housing units)
SEWAGE DISPOSAL
SEWPUB Public sewer (percent of housing units)
SEWSEP Septic tank or cesspool (percent of housing units)
SEWOTH Other means of disposal (percent of housing units)
AGE OF HOUSING
MEDYRBLT Median year built
The following is from the on-line STF3A documentation (U.S. Bureau
of the Census, 1992):
The data on source of water were obtained from questionnaire item H15, which was asked at both occupied and vacant housing units. Housing units may receive their water supply from a number of sources. A common source supplying water to five or more units is classified as a "Public system or private company." The water may be supplied by a city, county, water district, water company, etc., or it may be obtained from a well which supplies water to five or more housing units. If the water is supplied from a well serving four or fewer housing units, the units are classified as having water supplied by either an "Individual drilled well" or an "Individual dug well." Drilled wells or small diameter wells are usually less than 1-1/2 feet in diameter. Dug wells are usually larger than 1-1/2 feet wide and generally hand dug. The category, "Some other source" includes water obtained from springs, creeks, rivers, lakes, cisterns, etc. The data on sewage disposal were obtained from questionnaire item H16, which was asked at both occupied and vacant housing units. This item was asked on a sample basis. Housing units are either connected to a public sewer, to a septic tank or cesspool, or they dispose of sewage by other means. A public sewer may be operated by a government body or by a private organization. A housing unit is considered to be connected to a septic tank or cesspool when the unit is provided with an underground pit or tank for sewage disposal. The category, "Other means" includes housing units which dispose of sewage in some other way.Questions about source of water and sewage disposal method were not included in the 2000 Census.
kjhitt@usgs.gov
kjhitt@usgs.gov