National Land Cover Data enhanced (NLCDE) with GIRAS data 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 NLCDE land use percentages for NAWQA ground water study areas (Land Use Studies and Subunit Surveys.) The land use data is from the 1990's vintage NLCD 30-m data enhanced with GIRAS data.
This is one of the ancillary GIS data layers developed to characterize NAWQA ground water studies for national synthesis of water-quality data.
The NLCDE input data set did not include Alaska and Hawaii.
The original NLCD land cover data does not portray some land-cover categories very well:
1) Orchards are underrepresented, especially in the east. This is apparent when comparing NLCD and 1992 Census of Agriculture county totals.
2) Alpine tundra is not represented at all in NLCD.
3) Transportation is lumped with commercial and industrial or is not captured at all in NLCD.
4) Residential areas (especially mature residential areas) are often misclassified as forest, grassland or agriculture in NLCD.
Ancillary data layers from GIRAS were used to modify NLCD by burning in certain land cover data from GIRAS to the NLCD land cover map. We decided against using TIGER roads data because of coding errors in the TIGER attribute data (August 2003).
GIRAS data provided: Orchards/Vineyards Tundra (alpine areas) ResidentialSpecific rules were followed to preserve as much information as possible in the result.
CHANGE NLCD TO: WHEN: PRESERVE NLCD WHEN NLCD IS:
Orchard GIRAS is Orchard Water, Urban,
and state is not Orchard, Urban Grasses
CA, FL, OR, WA
Tundra GIRAS is Tundra and Any category except
NLCD is Shrubland Shrubland and
or Herb. Grassland Herbaceous Grassland
Residential w/ forest GIRAS is Residential Water, Urban,
and NLCD is forest Urban Grasses, Wetlands
Residential w/o forest GIRAS is Residential Water, Urban,
and NLCD is not forest Urban Grasses, Wetlands
The gridded ground water study area was combined with the NLCDE 30-m grid to create a NCLDE grid of each study area. The next step was to compute the land use percent for each land use category as number of cells (COUNT) of each land use divided by the total number of cells in the study area (SUM) multiplied by 100.
For example, the percentage (LUPCT11) of LUC 11 (NLCDE land use code 11, open water) is calculated:
LUPCT11 = COUNT / SUM * 100
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 NLCDE data is indicated by land use code 99.
The fields are:
SUID NAWQA study unit SUCODE NAWQA study unit/network code AREAID Ground water boundary coverage LUPCT11 Percent of GW study area comprised of open water LUPCT12 Percent of GW study area comprised of perennial ice/snow LUPCT21 Percent of GW study area comprised of low-intensity residential LUPCT22 Percent of GW study area comprised of high-intensity residential LUPCT23 Percent of GW study area comprised of commercial/industrial/transportation LUPCT25 Percent of GW study area comprised of residential w/o forest (res from GIRAS) LUPCT26 Percent of GW study area comprised of residential w/ forest (res from GIRAS) LUPCT31 Percent of GW study area comprised of bare rock/sand/clay LUPCT32 Percent of GW study area comprised of quarries/strip mines/gravel pits LUPCT33 Percent of GW study area comprised of transitional LUPCT41 Percent of GW study area comprised of deciduous forest LUPCT42 Percent of GW study area comprised of evergreen forest LUPCT43 Percent of GW study area comprised of mixed forest LUPCT51 Percent of GW study area comprised of shrubland LUPCT61 Percent of GW study area comprised of orchards/vineyards/other LUPCT62 Percent of GW study area comprised of orchards/vineyards/other (GIRAS) LUPCT71 Percent of GW study area comprised of grasslands/herbaceous LUPCT72 Percent of GW study area comprised of tundra (GIRAS) LUPCT81 Percent of GW study area comprised of pasture/hay LUPCT82 Percent of GW study area comprised of row crops LUPCT83 Percent of GW study area comprised of small grains LUPCT84 Percent of GW study area comprised of fallow LUPCT85 Percent of GW study area comprised of urban/recreational grasses LUPCT91 Percent of GW study area comprised of woody wetlands LUPCT92 Percent of GW study area comprised of emergent herbaceous wetlands LUPCT99 Percent of GW study area comprised of "no data" SUM_PCT Sum of the percents of all the land use categories (approx. 100)
kjhitt@usgs.gov
kjhitt@usgs.gov