 Abstract
In 2009, the U.S. Geological Survey (USGS) developed a Spatially Referenced Regressions on Watershed Attributes (SPARROW) surface-water quality model for the Upper Colorado River Basin (UCRB) relating dissolved-solids sources and transport in the 1991 water year to upstream catchment characteristics. The SPARROW model focused on geologic and agricultural sources of dissolved solids in the UCRB and was calibrated using water-year 1991 dissolved-solids loads from 218 monitoring sites. A new UCRB SPARROW model is planned that will update the investigation of dissolved-solids sources and transport in the basin to circa 2010 conditions and will improve upon the 2009 model by incorporating more detailed information about agricultural-irrigation and rangeland-management practices, among other improvements. Geospatial datasets relating to circa 2010 rangeland conditions are required for the new UCRB SPARROW modeling effort. This study compiled geospatial datasets for the UCRB that relate to the biotic alterations and rangeland conditions of grazing, fire and other land disturbance, and vegetation type and cover. Datasets representing abiotic alterations of access control (off-highway vehicles) and sediment generation and transport in general, were also compiled. These geospatial datasets may be tested in the upcoming SPARROW model to better understand the potential contribution of rangelands to dissolved-solids loading in UCRB streams.
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First posted January 30, 2015
Geospatial Datasets Describing UCRB Rangeland Conditions (ZIP formatted files. To access, download and extract all)
- Bureau of Land Management Grazing ZIP (12.9 MB)
The shapefile contains 2,367 polygons of BLM grazing allotments within or bordering the UCRB (fig. 4). Attributes for the allotment polygons include the allotment name (ALLOT_NAME) and number (ST_ALLOT), the authorized number of "animal unit months" for the allotment (AUTH_AUMS), and the area of the allotment in both acres (AREA_acres) and square kilometers (AREA_km2).
- U.S. Forest Service Grazing ZIP (3.8 MB)
The shapefile contains 444 polygons of USFS grazing allotments within or bordering the UCRB (fig. 4). Attributes for the allotment polygons include the allotment name (RMU_NAME) and number (RMU_CN), the authorized number of animal unit months for the allotment (AUTH_AUMS), and the area of the allotment in both acres (AREA_acres) and square kilometers (AREA_km2). USFS-billed grazing is referred to as the "authorized" amount and is equivalent to BLM’s "billed" grazing (U.S. Government Accountability Office, 2005).
- Land Disturbance ZIP (26 MB)
These layers include temporal and spatial information on disturbances to the landscape as a result of management activities or natural events. Two types of grids are presented: yearly disturbance grids for 1999–2010 and a composite grid of the yearly disturbance grids that summarizes vegetation disturbance for 1999–2010. Spatially, all grids cover the entire UCRB and have a 30-meter pixel resolution.
- Existing Vegetation Type and Cover ZIP (540 MB)
These layers include information on the vegetation type and vegetation cover in 2010 in the UCRB. The 2010 existing vegetation cover (EVC) layer represents the vertically projected percent cover of the live canopy layer. The 2010 existing vegetation type (EVT) layer represents the species composition. Spatially, both grids cover the entire UCRB and have a 30-meter pixel resolution.
- 2010 Roads ZIP (172 MB)
This layer contains information about the location and type of roads in the UCRB in 2010. One value in the MAF/TIGER Feature Class Code (MTFCC) attribute field in the roads layer is S1500, named "Vehicular Trail (4WD)", and is described as "an unpaved dirt trail where a four-wheel drive vehicle is required" (table 5). The Vehicular Trail (4WD) attribute presents potential UCRB locations of off-highway vehicle use—an activity directly related to the "access controls" abiotic alteration in Weltz and others (2014) (table 5; fig. 7). The 2010 roads layer covers the entire UCRB.
- Rainfall-Runoff Erosivity ZIP (962 kB)
This tabular dataset presents the 1971–2000 average annual rainfall-runoff erosivity factor (R-factor) for the UCRB. The R-factor is a measure of the cumulative erosive force of individual precipitation events (Daly and Taylor, 2002). All other factors being constant, sediment generation from precipitation is directly proportional to the product of the total kinetic energy of a storm and the storm’s maximum 30-minute intensity. The mean annual R-factor is a sum of this product for all storms in a year, averaged over all years of record (Daly and Taylor, 2002).
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U.S. Department of the Interior |
U.S. Geological Survey