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[an error occurred while processing this directive]precipsw | |
Data format: Raster Dataset File or table name: precipsw Coordinate system: State Plane Coordinate System 1983 Theme keywords: Precipitation, Rainfall, Vulnerability, Ratings |
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Abstract:
Average annual precipitation classes to characterize watersheds is one of 6 data
sets updated for the North Carolina Public Water Supply, Source Water Assessment Program. These data are used to rate the susceptibility of public water supplies in North Carolina to contamination.
The original dataset was produced in 2000. This version is updated to reflect new data sources.
This data set represents the ratings applied to the average annual
precipitation classes for use in the rating of the watershed
characteristics for surface-water suppliers.
Average annual precipitation is used as a measure of the amount of water
(with or without contaminants) that travels as runoff or through the
shallow subsurface to streams or lakes. For surface-water systems,
the greater the average annual precipitation, the higher the rating
applied on a scale of 1 to 10. |
Metadata elements shown with blue text are defined in the Federal Geographic Data Committee's (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM). Elements shown with green text are defined in the ESRI Profile of the CSDGM. Elements shown with a green asterisk (*) will be automatically updated by ArcCatalog. ArcCatalog adds hints indicating which FGDC elements are mandatory; these are shown with gray text.
Average annual precipitation classes to characterize watersheds is one of 6 data sets updated for the North Carolina Public Water Supply, Source Water Assessment Program. These data are used to rate the susceptibility of public water supplies in North Carolina to contamination. The original dataset was produced in 2000. This version is updated to reflect new data sources. This data set represents the ratings applied to the average annual precipitation classes for use in the rating of the watershed characteristics for surface-water suppliers. Average annual precipitation is used as a measure of the amount of water (with or without contaminants) that travels as runoff or through the shallow subsurface to streams or lakes. For surface-water systems, the greater the average annual precipitation, the higher the rating applied on a scale of 1 to 10.
This data set is to be used in a hydrologic analysis with other data sets to rate the unsaturated zone for public ground-water supplies and watershed characteristics for public surface-water supplies in North Carolina. For ground-water supplies, the factors used to rate susceptibility to contamination include vertical hydraulic conductance, land-surface slope, land cover, and land use. The selected factors used to devise ratings for surface-water supplies' susceptibility to contamination are average annual precipitation, land-surface slope, land cover, land use, and ground-water contribution.
The 1996 Amendments to the Safe Drinking Water Act require that each state prepare a source-water assessment for all public water supplies. States are required to (1) delineate source areas supplying wells and surface-water intakes, (2) inventory potential contaminant sources within the delineated source areas, and (3) determine the susceptibility of wells or intakes to the inventoried potential contaminant sources. In North Carolina, the lead agency charged with this task is the Public Water Supply Section (PWSS) of the Division of Environmental Health, Department of Environment and Natural Resources (DENR). North Carolina's Source Water Assessment Program (SWAP) provides assessments of each public drinking water intake in North Carolina. These assessments provide a relative susceptibility rating calculated using state-wide data. The U.S. Geological Survey (USGS) cooperated with the PWSS to provide components of the inherent vulnerability rating that was used with the contaminant rating to determine the overall susceptibility rating of source water supplies. To assist the PWSS with rating ground water inherent vulnerability, the USGS compiled the unsaturated zone rating based on the following characteristics: vertical hydraulic conductance, depth to water, land surface slope, land use and land cover. The watershed characteristic rating includes average annual precipitation, land surface slope, land use, land cover and groundwater contribution. The SWAP program has planned for updates to the initial ratings as conditions change and new data sources become available. The initial data used to calculate the unsaturated zone ratings and watershed characteristics ratings were compiled from sources from the late 1990's. Critical data layers have been updated since the ratings were calculated. These improved data layers need to be used in the ongoing update of the susceptibility ratings. Overlay and index methods for rating susceptibility to contamination of the unsaturated zone for ground-water suppplies, and watershed characteristics for surface-water supplies were derived for use by the State of North Carolina in assessing more than 11,000 public water-supply wells and approximately 245 public surface-water intakes. Factors that influence the inherent vulnerability of ground water and surface water were selected and assigned ratings on a scale of 1 to 10. These factors were then assigned weight to reflect their relative influence on inherent vulnerability and the reliability of the data. The values for each factor were obtained from geographic information system (GIS) data layers that were transformed into ARC/INFO raster data sets known as grids. These raster data sets have 30-meter by 30-meter cells, and each cell is assigned a weighted- factor value. Limitations -- The overlay and index methods of unsaturated zone and watershed characteristics ratings are broad-stroke methods that assess vulnerability on the basis of expert opinion. The methods aslo have limitations in the age and scale of the hydrologic and geographic data. But the most significant limitation of the methods used is that no statistical confirmation of the results have been performed. AVERAGE ANNUAL PRECIPITATION: Precipitation is a surrogate measure of the volume of water transported to surface-water intakes, with or without contaminants. In North Carolina, average annual precipitation varies from about 37 inches to more than 97 inches. Most of the variation occurs in the Blue Ridge Mountains, with the highest and lowest amounts occurring in this area. Determination of average annual precipitation is based on the recently-developed Parameter-elevation Regressions on Independent Slopes Model (PRISM), which uses land-surface elevation to estimate precipitation in areas not covered by weather observation stations (Daly, 1996). Average annual precipitation values, based on data collected from 1971 to 2007 at about 140 observation stations in North Carolina, are the input data to the PRISM model. The average annual precipitation was updated to reflect a more recent period of record. The annual average precipitation rating in 2000 was based on the years 1961 through 1990. The current data set covers the period 1971 to 2007. This reflects changes from recent hurricanes as well as two major droughts that occurred in N.C. during 1998-2002 and again in 2008 (McSwain, K.B., and Weaver, J.C., 2008, Effects of the current drought on streamflow and ground-water conditions in North Carolina: Charlotte, NC, Geological Society of America Southeastern Section Meeting [abs].; and Weaver, J.C., 2005, The drought of 1998-2002 in North Carolina?Precipitation and hydrologic conditions: U.S. Geological Survey Scientific Investigations Report 2005-5053, 88 p.) There was an increase in tropical storm and hurricane activity that affected North Carolina during this period. According to the State Climate Office of North Carolina, 38 tropical storms or hurricanes affected North Carolina during the period 1971 to 2007. There were only 19 during the period 1961 to 1990 (http://www.nc-climate.ncsu.edu/climate/hurricane.php). Average annual precipitation was categorized by increments of 5 inches, from less than 40 inches to more than 80 inches. Two-thirds of the State receives between 40 and 50 inches of rainfall during the year and have a precipitation rating of 2 or 3. Average annual precipitation amounts exceeding 80 inches are rated 10. The upper threshold of 80 inches was chosen because very few water-supply systems have watersheds located solely where rainfall exceeds this amount. Average annual precipitation categories and rating for watershed characteristics rating: >Average annual precipitation, Percent of area Rating >in inches in North Carolina > >Less than or equal to 40 1 1 > >Greater than 40 to 39 2 >less than or equal to 45 > >Greater than 45 to 32 3 >less than or equal to 50 > >Greater than 50 to 19 4 >less than or equal to 55 > >Greater than 55 to 7 5 >less than or equal to 60 > >Greater than 60 to 1 6 >less than or equal to 65 > >Greater than 65 to 1 7 >less than or equal to 70 > >Greater than 70 to less than 1 8 >less than or equal to 75 > >Greater than 75 to less than 1 9 >less than or equal to 80 > >Greater than 80 1 10 SELECTED REFERENCES: Daly, C., 1996, Overview of the PRISM model, PRISM Climate Mapping Program: accessed March 18, 1999, at URL http://www.ocs.orst.edu/prism/prism_new.html Daly, C., Neilson, R. P. and Phillips, D. L., 1994, A statistical- topographic model for mapping climatological precipitation over mountainous terrain: Journal of Applied Meteorology 33: p. 40-158. Eimers, J. L., Weaver, J. C., Terziotti, S., and Midgette, R. W., 2000, Methods of rating unsaturated zone and watershed characteristics of public water supplies in North Carolina: U. S. Geological Survey Water-Resources Investigations Report 99-4283, 31 p. North Carolina Department of Environment and Natural Resources, 1999, North Carolina source water assessment program plan: Raleigh, North Carolina Department of Environment and Natural Resources, Division of Environmental Health, Public Water Supply Section, [variously paged]. For more information on PRISM data see: Daly, C., 1996, Overview of the PRISM model: accessed March 18, 1999, at URL http://www.ocs.orst.edu/prism/prism_new.html DISCLAIMER: Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in ARC/INFO format, this metadata file may include some ARC/INFO-specific terminology.
Based on 20 years of record
These data are not to be used for site specific analysis
3916 Sunset Ridge Road
The authors are grateful to colleagues in the Public Water Supply Section of the Division of Environmental Health, North Carolina Department of Environment and Natural Resources (DENR) for their assistance in this collaborative project: thanks to Robert Midgette, Protection and Enforcement Branch Head; Amy Axon,hydrogeologist - Source Water Protection; and David Hammermann, Geographic Information Systems Specialist. The authors also thank the USGS report review team for their review of the update procedures: Jeanne Robbins, Surface-water Specialist; Melinda Chapman, Ground-water Specialist; Mary Giorgino, Water-quality Specialist; and Douglas Harned, ALBE-National Water Quality Assessment Project Chief.
The values for average annual rainfall are consistent with other Weather Service maps showing rainfall patterns.
Not applicable for raster data.
The data is available for all of N.C. and adjacent States. As updated data is available for more recent period of record, this data set could be updated.
No checks were made on horizontal accuracy other than visual checks with other data sources mapped at similar scales.
average annual precipitation
methods used to generate model
p. 40-158
methods
Created a 30-meter Grid data set of NC and adjacent states by resampling the 1971-2000 800 meter grid
Created a grid of each of the years 2001 through 2007
Create a mean grid of all years of data to get the average annual precipitation amounts from 1971 - 2007
Used the following remap table to change the classes to a rating from 1 to 10. (Using the Arc/Info GRID command, SLICE, with the TABLE option). >40 : 1 >45 : 2 >50 : 3 >55 : 4 >60 : 5 >65 : 6 >70 : 7 >75 : 8 >80 : 9 >120 : 10 >
Metadata imported.
Internal feature number.
ESRI
> >Value attribute table, PRECIPSW.VAT: > >COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME > 1 VALUE 4 10 B - > 5 COUNT 4 10 B - > 9 PCT_TOT 4 8 F 2 > 13 SQMI 4 8 F 2 > VALUE is rating: valid values are integers between 1 and 10, inclusive. COUNT is the number of 30-meter by 30-meter cells in the entire data set that have the rating. PCT_TOT is the percent of the total area just within NC for each category. SQMI is the conversion from 30 meter by 30 meter cells to square miles for just the NC portion of the study area. > >VALUE COUNT PCT_TOT SQMI > 1 3938485 0.60 320.77 > 2 173700622 38.83 20891.04 > 3 117104416 31.84 17131.79 > 4 52465471 18.51 9958.23 > 5 17335475 6.61 3555.14 > 6 5078301 1.17 626.98 > 7 3105866 0.80 431.70 > 8 1371126 0.42 224.21 > 9 880806 0.44 238.06 > 10 771423 0.48 259.11 > >Summary Statistics Table, PRECIPSW.STA: > >COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME > 1 MIN 8 15 F 3 > 9 MAX 8 15 F 3 > 17 MEAN 8 15 F 3 > 25 STDV 8 15 F 3 > MIN is the minimum value of item VALUE. MAX is the maximum value of item VALUE. MEAN is the average value of item VALUE. STDV is the standard deviation of item VALUE. > > MIN MAX MEAN STDV > 1.000 10.000 2.869 1.158 >
none
3916 Sunset Ridge Rd.
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Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.
3916 Sunset Ridge Road