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This web site contains the Federal Geographic Data Committee-compliant metadata (documentation) for digital data produced for the North Carolina, Department of Environment and Natural Resources, Public Water Supply Section, Source Water Assessment Program. The metadata are for 11 individual Geographic Information System data sets. An overlay and indexing method was used with the data to derive a rating for unsaturated zone and watershed characteristics 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 for susceptibility to contamination. For ground-water supplies, the digital data sets used in the assessment included unsaturated zone rating, vertical series hydraulic conductance, land-surface slope, and land cover. For assessment of public surface-water intakes, the data sets included watershed characteristics rating, average annual precipitation, land-surface slope, land cover, and ground-water contribution. Documentation for the land-use data set applies to both the unsaturated zone and watershed characteristics ratings. Documentation for the estimated depth-to-water map used in the calculation of the vertical series hydraulic conductance also is included.
Overlay and index methods for rating the unsaturated zone and watershed characteristics 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 for susceptibility to contamination. Factors that influence the vulnerability of public ground water and surface water supplies to contamination were selected and assigned ratings on a scale of 1 to 10, covering the range of values in North Carolina. These factors then were assigned weight to reflect their relative influence on the perceived inherent vulnerability and reliability of the data (Eimers and others, 2000).
Factors selected for rating the vulnerability to contamination of the unsaturated zone are vertical series hydraulic conductance, land-surface slope, land cover, and land use. Vertical series hydraulic conductance measures the capacity of unsaturated material to transmit water. Land-surface slope influences whether precipitation runs off land surfaces or infiltrates into the subsurface. Land cover describes the physical overlay of the land surface, which influences the amount of precipitation that runs off or infiltrates into the subsurface. Land use describes activities occurring on the land surface that influence the potential generation of nonpoint-source contamination.
In order to develop the unsaturated zone vulnerability rating, an estimated depth-to-water map was created. The estimated depth-to-water map was necessary for the calculation of the vertical series hydraulic conductance values. A documentation file was created describing methods and formulas that were applied to generate this data set.
Factors selected for rating the watershed characteristics upstream from surface-water intakes are average annual precipitation, land-surface slope, land cover, land use, and ground-water contribution. The average annual precipitation represents the amount of water available for transport in a watershed. Land-surface slope, land cover, and land use have similar influences on watershed characteristics as those identified for the unsaturated zone. Ground-water contribution represents the part of streamflow that is derived from ground water.
The values for each factor were obtained from Geographic Information System (GIS) data layers stored as raster data sets. These raster data sets have 30-meter by 30-meter cells, and each cell is assigned a value based on the characteristics of the factor within that cell. Only one data set was created for the land-use factor because identical ratings were applied for the unsaturated zone rating and watershed characteristics rating. The values for each factor were assigned a weight, then the weighted values were combined to create the final vulnerability values for the unsaturated zone and watershed characteristics ratings.
A structured documentation file (known as "metadata") for each data set has been created. The documentation files comply with the Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (Federal Geographic Data Committee, 1994). The FGDC-compliant metadata files contain descriptions of the data sets and include narrative sections describing the procedures used to produce the data sets in digital form. The metadata also include references of the sources used to create the data set.
This page provides background context for the 11 digital data sets created for the North Carolina Source Water Assessment Program (SWAP), and is the access point for all associated metadata files.
The FGDC-compliant metadata for the 11 data sets are linked below. The digital data are not currently online because of space limitations. The digital data sets can be requested through the distribution contact identified in the metadata.
Eimers, J.L., Weaver, J.C., Terziotti, Silvia, 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.
Federal Geographic Data Committee, 1994, Content standards for digital geospatial metadata (June 8): Washington, D.C., Federal Geographic Data Committee, 78 p.
Metadata is also available as a Plain Text file.
Vertical series hydraulic conductance classes is one of 11 data sets developed for the North Carolina Source Water Assessment Program. These data are used to rate the susceptibility of public water supplies in North Carolina to contamination.
This data set represents the ratings applied to conductance classes for use in the rating of the unsaturated zone for public ground-water suppliers.
The harmonic mean hydraulic conductance of a series of layers of unsaturated material provides a single value for the capacity of the entire sequence of the unsaturated zone to transmit water (with or without contaminants) from the land surface to the water table. For ground-water systems, the higher the conductance of the unsaturated zone, 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 Federal Safe Drinking Water Act (SDWA) Amendments of 1996 emphasize pollution prevention as an important strategy for the protection of ground-water and surface-water resources. This new focus in the SDWA promotes the prevention of drinking water contamination as a cost-effective means of ensuring reliable, long-term, and safe drinking water sources for public water-supply systems (North Carolina Department of Environment and Natural Resources, 1999a). Specifically, Section 1453 of the SDWA Amendments requires that States develop and implement a Source Water Assessment Program (SWAP) to delineate source water areas, inventory potential contaminants in these areas, and determine the susceptibility of each public water supply to contamination. The agency charged with the task of susceptibility assessment in North Carolina is the Public Water Supply Section (PWSS) of the Department of Environment and Natural Resources. The U.S. Geological Survey (USGS) is directed under the Clean Water Action Plan, funded by Congress in 1999, to assist States with water-quality monitoring and susceptibility determinations.
The inherent vulnerability rating is a measure of the potential for contaminants within a delineated source area to reach the ground-water or surface-water supply. The inherent vulnerability of a ground-water source of public water supply is determined by combining an aquifer rating and an unsaturated zone rating (North Carolina Department of Environment and Natural Resources, 1999a). The inherent vulnerability of a surface-water source of public water supply is determined by combining a watershed classification, intake location, raw water quality (water plant data), North Carolina Division of Water Quality Use Support rating, and watershed characteristics rating (North Carolina Department of Environment and Natural Resources, 1999a). In cooperation with the PWSS, the USGS developed methods to rate unsaturated zones for public ground-water systems and watershed characteristics for public surface-water intakes. All other components of inherent vulnerability were compiled by the PWSS.
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.
The identification of factors, development of ratings for each, and subsequent assignment of weights were based on (1) a literature search, which included examination of potential factors and their effects on the drinking-water quality; and (2) consultation with experts in the fields of hydrology, geology, forestry, agriculture, and water management. The relative rating of the unsaturated zone and watershed characteristics combines hydrologic data with expert knowledge to assess the vulnerability of water supplies to contamination.
Factors selected for rating the inherent vulnerability of the unsaturated zone to contamination are vertical series hydraulic conductance, land-surface slope, land cover, and land use. Vertical series hydraulic conductance measures the capacity of the unsaturated material to transmit water. Land-surface slope influences whether precipitation runs off land surfaces or infiltrates into the subsurface. Land cover describes the physical overlay of the land surface, which influences the amount of precipitation that runs off or infiltrates into the subsurface. Land use describes activities occurring on the land surface that influence the potential generation of nonpoint-source contamination.
Factors selected for rating vulnerability to contamination of the watershed upstream from surface-water intakes are average annual precipitation, land-surface slope, land cover, land use, and ground-water contribution. The average annual precipitation represents the mass of water that becomes available for transport in a watershed. Land-surface slope, land cover, and land use have similar influences on watershed characteristics as those identified for the unsaturated zone. In the cases of land-surface slope and land cover, the ratings for watershed characteristic vulnerability are the opposite of unsaturated zone vulnerability to contamination (i.e. more infiltration or ponding produces a higher vulnerability to ground-water, but less to surface-water sources.) Ground-water contribution represents the part of streamflow that is derived from ground-water discharge.
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.
VERTICAL SERIES HYDRAULIC CONDUCTANCE:
Vertical hydraulic conductance over the entire thickness of the unsaturated zone, C, is calculated for layers in series:
1/C = 1/C1 + 1/C2 + 1/C3
where Ci (i = 1, 2, or 3) is the vertical hydraulic conductance of each layer, i, of the unsaturated zone. For each layer, i, Ci is defined as:
Ci = ( Kvi A ) / bi
where Kvi is the vertical hydraulic conductivity, Kv, of layer i; A is a unit area normal to the vertical direction, and bi is the unsaturated thickness of layer i.
Unsaturated vertical hydraulic conductivity is a function of moisture content, porosity, and other textural aspects of the material (O'Hara, 1996). Saturated hydraulic conductivity is the upper bound of the possible range of values for unsaturated hydraulic conductivity (Freeze and Cherry, 1979). Saturated Kvi is used in this study as a conservative estimate of unsaturated Kvi for layer i. Because unsaturated hydraulic conductivity is difficult to estimate, this substitution is commonly made (O'Hara, 1996).
Depending on depth to water and the occurrence of a given layer at any location, the Blue Ridge and Piedmont Provinces can include layers of soil, saprolite, and(or) crystalline bedrock. The Coastal Plain Province can include soil layers and(or) sedimentary units.
SOILS:
Two soil data sets were used to create this data set-- county-level data and state-level data. County-level soil types were identified in the Soil Survey Geographic Database (SSURGO) of the Natural Resources Conservation Service (NRCS). The NRCS developed the SSURGO database at a scale of 1:24,000 primarily for use in farms and ranches, landowners and land users, townships, or natural-resource planning and management of counties. At the time of this report, county-level data were processed for 73 of the 100 counties in North Carolina:
ALAMANCE, ALEXANDER, ALLEGHANY, ASHE, BEAUFORT, BERTIE, BLADEN, BRUNSWICK, CABARRUS, CALDWELL, CAMDEN, CARTERET, CHOWAN, COLUMBUS, CRAVEN, CUMBERLAND, CURRITUCK, DARE, DAVIDSON, DAVIE, DUPLIN, DURHAM, EDGECOMBE, FORSYTH, FRANKLIN, GASTON, GATES, GRANVILLE, GREENE, GUILFORD, HALIFAX, HARNETT, HAYWOOD, HERTFORD, HOKE, HYDE, JACKSON, JOHNSTON, JONES, LENOIR, MACON, MARTIN, MCDOWELL, MECKLENBURG, MITCHELL, MOORE, NASH, NEW_HANOVER, NORTHAMPTON, ONSLOW, ORANGE, PAMLICO, PASQUOTANK, PENDER, PERQUIMANS, PERSON, PITT, POLK, RANDOLPH, RICHMOND, ROBESON, ROCKINGHAM, SAMPSON, SCOTLAND, STANLY, TYRRELL, UNION, WAKE, WASHINGTON, WAYNE, WILKES, WILSON and YANCEY.
Where county-level soil information was not available, the State Soil Geographic (STATSGO) database for North Carolina was used. STATSGO is a digital, general soil-association map developed by the NRCS. It consists of a broad inventory of soil and non-soil areas that occur in a repeatable pattern on the landscape and that can be cartographically shown at the scale mapped. The soil maps for STATSGO were compiled by generalizing more detailed soil surveymaps. Where more detailed soil survey maps were not available, data on geology, topography, vegetation, and climate were assembled together with Land Remote Sensing Satellite (LANDSAT) images. Soils of like areas were studied, and the probable classification and extent of the soils were determined. STATSGO was mapped at 1:250,000 scale and was designed primarily for regional, multicounty, river basin, State, and multistate resource planning, management, and monitoring.
The STATSGO and SSURGO soil layers were compiled into one layer with a cell size of 30-meters by 30-meters. The SSURGO data were superimposed on the STATSGO data so that the best available data were always used.
Information about soil permeability and thickness was obtained from the Map Unit Interpretations Record (MUIR) attribute database, which is linked to the SSURGO soil-unit delineation and the STATSGO mapping unit. The MUIR database contains information about soils and individual layers within soils.
ARC/INFO programs were written to process the MUIR data to extract thickness and permeability by layer for each soil unit. For SSURGO data layers, total thickness and harmonic mean permeability were calculated for each soil type. For STATSGO data, the weightedaverage by percent of each soil component was applied to each mapping unit for thickness and harmonic mean permeability. The body of the report defines the equations used to calculate the harmonic mean permeability values. Note that soil permeability as defined by NRCS is equivalent to soil hydraulic conductivity.
Depth-to-water estimates used in developing vertical series hydraulic conductance of the unsaturated zone are explained in Eimers and others (2001).
METHOD OF ESTIMATING CONDUCTANCE:
Vertical and horizontal hydraulic conductivity data were obtained from pollution-incident reports, non-discharge (spray irrigation) permitting reports for onsite wastewater disposal sites, and the ground-water and underground storage tank permitting reports of the North Carolina Department of Environment and Natural Resources (NCDENR), as well as from the U.S. Geological Survey (USGS), East Carolina University, and North Carolina State University.
Data were selected for inclusion only when documentation indicated that hydraulic conductivity measurements pertained to the unconfined aquifer and when a geographic location could be determined, typically from a map in a consultant's report.
At most sites, only horizontal hydraulic conductivity estimates, Kh, were available. For each site at which both Kh and Kv estimates were available, the ratio of Kh to Kv was calculated. The mean ratio of Kh to Kv was determined for all sites within a geologic unit. At sites where only Kh estimates were available, the mean ratio of Kh to Kv was used to derive an estimate of Kv.
In order to provide geographically distributed estimates, an attempt was made to acquire a minimum of five horizontal conductivity values for each of the 100 counties in North Carolina. However, data were limited for many counties. Photocopies of pertinent information, including a location map, were obtained for each site having hydraulic conductivity measurements for the unconfined aquifer. USGS data included hydraulic conductivity estimates obtained during investigations at Fort Bragg. Two East Carolina University theses contained vertical hydraulic conductivity data. Pertinent data and location maps were photocopied from these two theses. Comparisons of final estimates were made with data summaries in Amoozegar and others (1991), and Amoozegar, Hoover, and others (1993).
Techniques used to determine Kh included aquifer tests, slug tests, and grain-size analysis (Hazen, 1911). Techniques used to determine Kv included constant head permeability tests and extended aquifer tests (Moench, 1993; Neuman, 1997) for fully and partially penetrating wells, respectively). Few values were available for Kv.
Anisotropy of a medium is commonly expressed as the ratio of vertical to horizontal hydraulic conductivity and is associated with the shape and depositional pattern of the particles. A ratio of Kv to Kh was calculated for each of the sites for which a Kv value was reported. The mean Kv/Kh was calculated for each hydrogeologic unit, where mean (Kv/Kh) is 1/n times the sum of all n of these Kv/Kh.
The geometric mean of Kh, G(Kh,n), for a given site with n-estimated Kh values, was multiplied by the corresponding mean Kv/Kh value to compute an estimated Kv (Kv-est) for each site. The estimated vertical hydraulic conductivity, Kv-est, is mean (Kv/Kh) times G(Kh,n). The median Kv-est for each hydrogeologic unit was used for the subsequent analysis.
CONDUCTANCE OF SEDIMENTARY FORMATIONS (Kv_sed):
Vertical and horizontal hydraulic conductivity estimates were compiled from 662 wells at 256 sites, (fewer vertical hydraulic conductivity values were available). NCDENR offices in Fayetteville, Raleigh, Washington, and Wilmington were visited as part of this effort.
The seven hydrogeologic units used in this analysis correspond to those assigned to the mid-Atlantic Coastal Plain by Ator and others (2000). Unit designations primarily are based on physiography and average grain size of the surficial materials. Characteristics of the hydrogeologic units are presented in Ator and others (2000). The hydrogeologic unit for each site was determined by locating the site on digitized 7.5-minute USGS topographic maps and overlaying the site location on a digital coverage of the hydrogeologic units.
The number of Kv values per hydrogeologic unit ranged from seven for unit 1 to none for unit 5. Kv values predominantly were present in the reports submitted for high-volume non-discharge permits, which primarily involve spray-irrigation disposal of wastewater. Because sites selected for spray irrigation typically are those with high vertical permeability, this data set may overestimate the Kv of a given area (for example, low permeability sites, such as pocosins or other poorly drained areas, will not likely be candidate sites for spray irrigation facilities). Overestimation of Kv will result in a higher susceptibility rating for ground-water contamination.
Kv/Kh ratios generally were in agreement for a given hydrogeologic unit and ranged from 0.188 for hydrogeologic unit 1 to 0.004 for hydrogeologic unit 3.
The median Kv-est for each hydrogeologic unit was used for the subsequent analysis. Because no Kv data were available for the hydrogeologic unit referred to as unit 5 (middle Coastal Plain, deeply-dissected sands), the average Kv/Kh value for unit 4 (middle Coastal Plain, sands with overlying gravels) was used to estimate Kv. A summary of sedimentary unit hydraulic conductivity data by surficial hydrogeologic unit for the Coastal Plain Province is provided below:
Hydro- Number Number Number Mean Median Maximum Minimum geologic of of of Kv Kv/Kh Kv Kv Kv Unit Sites Wells values -------------------------------------------------- [feet/day] 1. 60 145 7 0.188 1.133 58.092 0.001 2. 68 205 3 0.010 0.015 1.571 <0.001 3. 8 11 2 0.004 0.004 0.084 <0.001 4. 64 170 2 0.073 0.078 12.351 0.001 5. 7 25 0 0.073* 0.036 0.816 0.020 6. 17 36 1 0.031 0.341 6.573 0.017 7. 30 70 2 0.015 0.051 1.284 0.003 where the hydrogeologic units are: 1. Coastal lowlands 2. Middle Coastal Plain, mixed sediments 3. Middle Coastal Plain, fine sediments 4. Middle Coastal Plain, sands with overlying gravels 5. Middle Coastal Plain, deeply dissected sands 6. Inner Coastal Plain 7. Alluvial and estuarine valleys * No Kv values available for hydrogeologic unit 5; used estimates for hydrogeologic unit 4.
CONDUCTANCE OF SAPROLITE AND CRYSTALLINE BEDROCK (Kv_sap):
Site visits were conducted at regional NCDENR offices located in Asheville, Mooresville, Winston-Salem, and Raleigh to obtain Kv and Kh records. Over 650 well records from 257 sites in the Blue Ridge and Piedmont Provinces were copied and the data were transferred to electronic files that contained the locations and Kv and Kh values.
The vertical hydraulic conductance values of the saprolite layer were estimated on the basis of simplified geologic units for the Piedmont and Blue Ridge Provinces. The four geologic units used in this analysis are simplified geologic units presented by Trapp and Horn (1997).
Very few actual Kv values were found, so Kv/Kh values were used to estimate Kv for four geologic units in the two provinces. The following is a summary of saprolite hydraulic conductivity data by surficial geologic unit for the Piedmont and Blue Ridge Provinces:
Geologic Number Number Number Mean Median Maximum Minimum Unit of of of Kv Kv/Kh Kv Kv Kv sites wells values -------------------------------------------------- [feet/day] 1. 15 37 1 0.307 0.072 0.072 0.072 2. 50 126 3 0.063 0.023 0.586 0.001 3. 59 160 5 0.008 0.006 0.241 <0.001 4. 133 332 7 0.148 0.099 4.853 <0.001 where the geologic units are: 1. Lower Mesozoic sedimentary and igneous rocks (Mzl) 2. Cambrian metavolcanic rocks and Paleozoic sedimentary and metasedimentary rocks (CPzm) 3. Silurian through Cambrian phyllite, quartzite, and mica schist (SC); Precambrian quartzite, mica schist, and gneiss (pCq); and Precambrian mica schist and gneiss (pCs) 4. Upper Paleozoic cataclastic rocks (Pzu); lower Paleozoic and Precambrian felsic gneiss (PzpCf); and lower Paleozoic andPrecambrian granite gneiss and granite (PzpCg)
One value for the vertical hydraulic conductance of the crystalline bedrock layer was estimated for all of the Piedmont and Blue Ridge Provinces.
At the regional NCDENR offices in Asheville, Mooresville, Winston-Salem, and Raleigh, 65 well records from 35 sites were identified as having estimates for crystalline bedrock hydraulic conductivity. It was assumed that Kh = Kv in the crystalline bedrock. The median hydraulic conductivity value of 0.271 feet/day was used everywhere in the Piedmont and Blue Ridge Provinces. Thus,
Kv bedrock = 0.271 feet/day Crystalline | Number Number Median Minimum Maximum bedrock | of of Kv Kv Kv | sites wells | ------------------------------------ | [feet/day] | | 35 65 0.271 <0.001 114.0
CLASSIFICATION OF VERTICAL SERIES HYDRAULIC CONDUCTANCE:
Vertical series hydraulic conductance categories were divided into the same classes used in a previous study (O'Hara, 1994) and assigned ratings from 1 to 10. Low ratings were assigned to the low conductance, and high ratings were assigned to the high conductance. Areas characterized by low vertical series hydraulic conductance contribute the least to the inherent vulnerability of ground-water supplies, and areas characterized by high vertical series hydraulic conductance contribute the most to the inherent vulnerability of ground-water supplies.
Vertical series hydraulic conductance categories and rating values for unsaturated zone rating [after O'Hara, 1996] Vertical series hydraulic Rating conductance categories (feet-squared per day) Less than or equal to 500 1 Greater than 500 to 2 less than or equal to 1,000 Greater than 1,000 to 3 less than or equal to 2,000 Greater than 2,000 to 4 less than or equal to 4,000 Greater than 4,000 to 5 less than or equal to 8,000 Greater than 8,000 to 6 less than or equal to 16,000 Greater than 16,000 to 7 less than or equal to 32,000 Greater than 32,000 to 8 less than or equal to 64,000 Greater than 64,000 to 9 less than or equal to 128,000 Greater than 128,000 10
ARC MACRO LANGUAGE (AML) PROGRAMS--
These AMLs are referred to in the following data processing steps:
calc_vcont_24k.aml
------------------
&do x &list orange jackson alamance
&echo &br
&work y:\county\%x%
&wat vcont_%x%.wat
&if [sho program] cn 'TAB' &then quit
&if [exists soils_24k.layeritems -info] &then &type [delete soils_24k.layeritems -info]
&if [quote [listitem soils_24k.layer -info -character]] nc 'MUSYM' &then
&do
tables
sel soils_24k.layer
redefine
9
musym,6,6,c
[unquote ' ']
q
&end
pullitems soils_24k.layer soils_24k.layeritems
musym
seqnum
layernum
layerid
laydepl
laydeph
perml
permh
end
&if [sho program] nc 'TAB' &then tables
additem soils_24k.layeritems thk,4,4,b
additem soils_24k.layeritems permm,4,8,f,2
additem soils_24k.layeritems vcont,4,8,f,2
additem soils_24k.layeritems inv_vcont,4,8,f,2
sel soils_24k.layeritems
calc thk = laydeph - laydepl
res perml le 0 and permh le 0
calc permm = 0
asel
res perml le 0 and permh gt 0
calc permm = 10 ** ( ( ( ln .00001 / ln 10 ) + ( ln permh / ln 10 ) ) / 2 )
asel
res perml gt 0 and permh le 0
calc permm = 10 ** ( ( ( ln perml / ln 10 ) + ( ln .00001 / ln 10 ) ) / 2 )
asel
res perml gt 0 and permh gt 0
calc permm = 10 ** ( ( ( ln perml / ln 10 ) + ( ln permh / ln 10 ) ) / 2 )
asel
res thk le 0
calc vcont = 0
nsel
calc vcont = permm / thk
ase
res vcont gt 0
calc inv_vcont = 1 / vcont
&wat &off
&end
q
&work d:\swap\soils
calc_hmp_24k.aml
----------------
&do x &list orange jackson alamance
&echo &br
&work y:\county\%x%
&wat calc_hmp_%x%.wat
&if [quote [listitem soils_24k.freq -info -red ]] nc 'MUSYM' &Then
&do
tables
sel soils_24k.freq
redefine
9
musym
6,6,c
[unquote ' ' ]
q
&end
&do x &list [unquote [sho cursors ]]
cursor %x% remove
&end
&if [exists soils_24k.hydgrp -info] &then &type [delete soils_24k.hydgrp -info]
pullitems soils_24k.comp soils_24k.hydgrp
musym
seqnum
compname
comppct
slopel
slopeh
hydric
hydgrp
end
&if [quote [listitem soils_24k.freq -info ]] nc 'HMP' &Then ~
additem soils_24k.freq soils_24k.freq hmp 4 8 f 4
/* calc the hmp value from up to 5 layers for each sequence of soils within a mapunit...
&if [sho program] nc 'PLOT' &Then ap
/* the soils_24k.freq file has the unique map unit ids...
cursor mu_cur declare soils_24k.freq info rw
cursor mu_cur open
&do &while %:mu_cur.aml$next%
&s thismu = %:mu_cur.musym%
/* the layeritems file has the information for each layer within each sequence...
asel soils_24k.layeritems info
res soils_24k.layeritems info musym = [quote %thismu%]
&s numlayers = [extract 1 [sho select soils_24k.layeritems info ]]
cursor vcont_cur declare soils_24k.layeritems info rw
cursor vcont_cur open
&s lay 0
&do &while %:vcont_cur.aml$next%
&s lay = 1 + %lay%
&s vcont%lay% = %:vcont_cur.vcont%
&s thk%lay% = %:vcont_cur.thk%
&s invcont%lay% = %:vcont_cur.inv_vcont%
cursor vcont_cur next
&end
cursor vcont_cur remove
&s sumvcont = 0
&s sumthk = 0
&s suminvcont = 0
&do x := 1 &to %numlayers%
&s sumvcont = %sumvcont% + [value vcont%x%]
&s sumthk = %sumthk% + [value thk%x%]
&s suminvcont = %suminvcont% + [value invcont%x%]
&end
&if %sumvcont% le 0 &then &s :mu_cur.hmp = 0
&else &s :mu_cur.hmp = %sumthk% / %suminvcont%
cursor mu_cur next
&end
cursor mu_cur remove
q
&end /* end the county loop
&work d:\swap\soils
&echo &off
&ret
addtables.aml
-------------
&do x &list granville hyde
&work y:\county\%x%
&if [quote [listitem soils_24k.pat -info -red ]] nc 'MUSYM' &Then
&do
&describe soils_24k
&s prec = %dsc$precision%
tables
sel soils_24k.pat
&if %prec% = 'SINGLE' &then
&do
redefine
17
musym
6,6,c
[unquote ' ' ]
&end
&else
&do
redefine
25
musym
6,6,c
[unquote ' ' ]
&end
q
&end
&do x &list HYDRIC HMP SLOPEL SLOPEH HYDGRP SEQNUM COMPNAME COMPPCT MINOR1
&if [quote [listitem soils_24k.pat -info ]] CN [QUOTE %X%] &Then ~
dropitem soils_24k.pat soils_24k.pat %X%
&END
joinitem soils_24k.pat soils_24k.freq soils_24k.pat dsl-name dsl-name
joinitem soils_24k.pat soils_24k.hydgrp soils_24k.pat musym dsl-name
&end
&ret
addthick_24.aml
---------------
&do x &list granville hyde
&work y:\county\%x%
&if [exists soils_24k.thk -info] &then &type [delete soils_24k.thk -info]
frequency soils_24k.layeritems soils_24k.thk
musym
end
thk
vcont
inv_vcont
end
&do x &list THK VCONT INV_VCONT
&if [quote [listitem soils_24k.pat -info ]] CN [QUOTE %X%] &Then ~
dropitem soils_24k.pat soils_24k.pat %X%
&END
joinitem soils_24k.pat soils_24k.thk soils_24k.pat musym hmp
&end
merge_soils.aml
---------------
&if [sho program] nc 'GRID' &then grid
/*setwindow d:\swap\proc_sw\huc14grd d:\swap\proc_sw\huc14grd
/*temp = polygrid(soils_250k,thk_awt, #, #, 60)
/* convert inches to feet
/*thk_250k = temp / 12
/*kill temp
/*temp = polygrid(soils_250k,hmp_awt, #, #, 60)
/* convert inches/hour to feet/day
/*hmp_250k = temp * 2
/*kill temp
&do x &list granville hyde
setwindow y:\county\%x%\soils_24k d:\swap\proc_sw\huc14grd
temp = polygrid (y:\county\%x%\soils_24k,thk,#,#,60)
/* convert inches to feet
temp2 = temp / 12
&if [exists y:\county\%x%\%x%thk -grid ] &then kill y:\county\%x%\%x%thk
copy temp2 y:\county\%x%\%x%thk
kill (! temp temp2 !)
/* temp = polygrid (y:\county\%x%\soils_24k,hmp,#,#,60)
/* convert inches/hour to feet/day
/* temp2 = temp * 2
/* &if [exists y:\county\%x%\%x%hmp -grid ] &then kill y:\county\%x%\%x%hmp
/* copy temp2 y:\county\%x%\%x%hmp
/* kill (! temp temp2 !)
&end
setwindow d:\swap\proc_sw\huc14grd d:\swap\proc_sw\huc14grd
/*soils_thk = merge (y:\county\beaufort\beaufortthk, y:\county\cabarrus\cabarrusthk, y:\county\currituck\currituckthk, y:\county\stanly\stanlythk, thk_250k)
/*soils_hmp = merge (y:\county\beaufort\beauforthmp, y:\county\cabarrus\cabarrushmp, y:\county\currituck\currituckhmp, y:\county\stanly\stanlyhmp, hmp_250k)
&if [exists soils_thk -grid] &then kill soils_thk
soils_thk = merge(y:\county\orange\orangethk, ~
y:\county\nash\nashthk, ~
y:\county\halifax\halifaxthk, ~
y:\county\edgecombe\edgecombethk, ~
y:\county\brunswick\brunswickthk, ~
y:\county\hyde\hydethk, ~
y:\county\guilford\guilfordthk, ~
y:\county\granville\granvillethk, ~
y:\county\durham\durhamthk, ~
y:\county\jackson\jacksonthk, ~
y:\county\alamance\alamancethk, ~
y:\county\beaufort\beaufortthk, y:\county\cabarrus\cabarrusthk, y:\county\currituck\currituckthk, y:\county\stanly\stanlythk, ~
thk_250k)
&ret
&if [exists soils_hmp -grid] &then kill soils_hmp
soils_hmp = merge(y:\county\orange\orangehmp, ~
y:\county\nash\nashhmp, ~
y:\county\halifax\halifaxhmp, ~
y:\county\edgecombe\edgecombehmp, ~
y:\county\brunswick\brunswickhmp, ~
y:\county\hyde\hydehmp, ~
y:\county\guilford\guilfordhmp, ~
y:\county\granville\granvillehmp, ~
y:\county\durham\durhamhmp, ~
y:\county\jackson\jacksonhmp, ~
y:\county\alamance\alamancehmp, ~
y:\county\beaufort\beauforthmp, y:\county\cabarrus\cabarrushmp, y:\county\currituck\currituckhmp, y:\county\stanly\stanlyhmp, ~
hmp_250k)
calc_conductivity.aml
---------------------
/* calc_conductivity.aml
/* this aml calculates the final vertical hydraulic conductance grid for the State
/* seterzio@usgs.gov
/*
/* earlier versions of this aml are in y:\soils
/**************************************************
/* This area defines the location and manipulation
/* necessary for each grid used within the calculations
/**************************************************
/* area in square feet
&s area = ( 30 * 30 * 10.763910 )
/* depth to water - getting rid of the -99 for water
&s dtw = ( float( con (h:\depth_to_water\state\dtw_state > -99, h:\depth_to_water\state\dtw_state)) / 100)
/* soil thickness based on SSURGO and STATSGO soil attributes
&s soilthk = ( float ( y:\soils\thk_ftx100 ) / 100 )
/* hmp value of soils based on SSURGO and STATSGO soil attributes
&s hmp = ( float( y:\soils\hmp_ftdayx10k) / 10000 )
/* Kv in coastal plain of sedimentary layer
&s kv_cpl = ( h:\bedrock\kv_cpl )
/* bedinsoil is the depth to bedrock of areas where bedrock is shallower than
/* soil thickness (just in the hard bedrock) and shallower than depth to water
/* Areas outside hard bedrock are coded -1
&s bedinsoil = ( float (h:\bedrock\bed_lt_soil) / 100)
/* dtbed is the depth to bedrock values just within the hard bedrock -
/* all other values are coded 99999
&s dtbed = ( float ( h:\bedrock\hardbed_dep ) / 100 )
/* kv in saprolite layer
&s kvsap = ( h:\bedrock\kv_sap2)
/* kv estimate in bedrock
&s kvbed = 0.271
setcell 30
/*************************
/* COASTAL PLAIN
/*************************
setwindow h:\depth_to_water\coastal_plain\cpl_grd y:\state\ncgrd
setmask h:\depth_to_water\coastal_plain\cpl_grd
&do x &list cond_cpl l_hmp_cpl l_kv_cpl
&if [exists %x% -grid] &then kill %x%
&end
/* for soil layer... for l (thickness of layer)
/* if depth to water lt soil thickness use the dtw thickness, else use
/* the soil thickness
l_hmp_cpl = con( %dtw% le %soilthk% , %dtw% / %hmp% , %soilthk% / %hmp% )
/* for sap layer... for l (thickness of layer)
/* if depth to water lt soilthickness => 0, else use dtw - soil thick
l_kv_cpl = con( %dtw% le %soilthk%, 0, ( ( %dtw% - %soilthk% ) / %kv_cpl% ) )
/* final conductance for coastal plain...
cond_cpl = con( isnull(%area% / ( l_hmp_cpl + l_kv_cpl ) ), 0, %area% / ( l_hmp_cpl + l_kv_cpl ) )
/*************************
/* Piedmont and Blue Ridge
/*************************
setwindow h:\bedrock\kv_sap2 y:\state\ncgrd
setmask h:\bedrock\kv_sap2
&do x &list cond_2 l_hmp l_kvsap l_kvbed
&if [exists %x% -grid] &then kill %x%
&end
/* soil layer...for l (thickness of layer)
/* check for bedrock thickness lt soil thickness, and depth to water lt
/* soil thickness
l_hmp = con( %bedinsoil% ge 0, %bedinsoil% / %hmp%, %dtw% le %soilthk%, %dtw% / %hmp%, %soilthk% / %hmp% )
/* saprolite layer...for l (thickness of layer)
/* check for bedrock thickness lt soil thickness, and depth to water lt soil
/* thickness => 0, if bedrock < dtw then use ( depth to bedrock - soil thick)
/* as thickness of sap, else use ( depth to water - soil thick) as
/* sap thickness.
l_kvsap = con(%bedinsoil% ge 0, 0, ~
%dtw% le %soilthk%, 0, ~
%dtbed% lt %dtw% , ( %dtbed% - %soilthk% ) / %kvsap%, ~
( %dtw% - %soilthk% ) / %kvsap% )
/* bedrock layer....for l (thickness of layer)
/* check for dtw lt dtbedrock, bedinsoil lt 0, => 0, else use dtw - depth to bed
l_kvbed = con ( %dtw% lt %dtbed% , 0, %bedinsoil% lt 0, 0, ( %dtw% - %dtbed% ) / %kvbed% )
/* final conductance for pied and blue ridge
cond_2 = con( isnull(%area% / ( l_hmp + l_kvsap + l_kvbed ) ), 0, %area% / ( l_hmp + l_kvsap + l_kvbed ) )
shadeset rainbow
gridsh cond_2 # linear
describe cond_2
setwindow y:\state\ncgrd h:\bedrock\kv_sap2
cond_nc = merge(cond_cpl, cond_2)
&ret
/* notes...
for conductivity apply the formula:
for coastal plain:
Area in ft2 / ( (thickness_of_soils / hmp ) + ( (depth_to_water - Thickness_soils ) / kv ) )
when depth to water is le thickness of soil, use the thickness above water table ( dtw )
when depth to water is le thickness of soil, kv = 0
when depth to water is gt thickness of soil, use depth to water below soils ( dtw - thick)
for Piedmont and Blue Ridge:
also need saprolite and
using bedrock where it is "hard" from STATSGO (hardbed250k == 1)
Area in ft2 / ( (thickness_of_soils / hmp ) + ( thickness_sap / kvsap) + ( thickness_bed / kvbed ) )
SELECTED REFERENCES:
Amoozegar, A., Hoover, M. T., Kleiss, H. J., Guertal, W. R., and Surbrugg, J. E., 1993, Evaluation of saprolite for on-site wastewater disposal: Water Resources Research Institute Report No. 279, 185 p.
Amoozegar, A., Schoeneberger, P. J., and Vepraskas, M. J., 1991, Characterization of soils and saprolites from the Piedmont region for waste disposal purposes: Water Resources Research Institute Report No. 255, 124 p.
Ator, S.W., Denver, J.M., and Hancock, T.C., 2000, Relating shallow Ground-water quality to surficial hydrogeology in the mid-Atlantic coastal plain in National Water Quality Monitoring Conference, Monitoring for the Millennium, April 25-27, 2000, Austin Texas, p.409-423.
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.
Hazen, Allen, 1911, Discussion: Dams on sand foundations. Transactions, American Society of Civil Engineers, vol. 73, p.199.
Moench, A.F. 1993, Computation of type curves for flow to partially penetrating wells in water-table aquifers. Ground Water, 34(4), p. 593-96.
Neuman, S.P., 1997, Flow to a well of finite diameter in a homogeneous, anisotropic water table aquifer. Water Resources Research, 33(6), p. 1397-1407.
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].
O'Hara, C. G., 1994, Permeability of soils in Mississippi: U.S. Geological Survey Water-Resources Investigations Report 94-4088, 1 sheet.
O'Hara, C.G., 1996, Susceptibility of ground water to surface and shallow sources of contamination in Mississippi: U.S. Geological Survey Hydrologic Investigations Atlas HA-739, 4 sheets.
Trapp, H., Jr., and Horn, M. A., 1997, Ground water atlas of the United States, Segment 11, Delaware, Maryland, New Jersey, North Carolina, Pennsylvania, Virginia, West Virginia: Hydrologic Investigations Atlas 730-L, 24 p.
More information on STATSGO, SSURGO, and the MUIR database can be found at the USDA-NRCS, National Soils Survey Center, National Soil Data Access Facility website, http://www.statlab.iastate.edu/soils/nsdaf/
URL updated October 5 2005:
http://soils.usda.gov/survey/
STATSGO data can be accessed from: http://www.ftw.nrcs.usda.gov/stat_data.html
URL updated June 23 2005:
http://www.ncgc.nrcs.usda.gov/
products/datasets/statsgo/
link
Information on the SSURGO data available through NC Center for Geographic Information and Analysis can be viewed at:
http://cgia.cgia.state.nc.us/
corpmeta.dir/corplayer.html
URL updated October 5 2005:
http://www.cgia.state.nc.us/cgdb/datalist.html
NRCS has some SSURGO data online at: http://www.ftw.nrcs.usda.gov/ssur_data.html
URL updated June 23 2005:
http://www.ncgc.nrcs.usda.gov/
products/datasets/ssurgo/index.html
link
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.
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; Elizabeth Morey, Hydrogeologist; Gale Johnson, Hydrogeologist; and Rajpreet Butalia, Geographic Information Systems Coordinator.
The authors also thank the following scientists and engineers who provided additional technical review of this work:
Richard Burns, Watershed and Forest Hydrologist, U.S. Forest Service, U.S. Department of Agriculture Ron Coble, Professional Geologist [Retired USGS] Ed Holland, Orange County Water and Sewer Authority Beth McGee, Clean Water Management Trust Fund Ted Mew, Groundwater Section, Division of Water Quality, North Carolina DENR Joe Rudek, Environmental Defense Fund Henry Wade, Pesticides Section, North Carolina Department of Agriculture Steve Zoufaly, Division of Water Quality, North Carolina DENR
The authors also thank the USGS report review team for their review of the metadata products: Stephen J. Char, Jason M. Fine, Michael L. Strobel, Douglas A. Harned and Rebecca J. Deckard.
Value Attribute Table, SOILSGW.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 2VALUE is the rating: valid values are integers 1 to 10, inclusive
list condgw.vat Record VALUE COUNT PCT_TOT SQMI 1 1 109019609 70.40 37883.25 2 2 8761097 5.66 3044.40 3 3 4050426 2.62 1407.48 4 4 4513368 2.91 1568.35 5 5 7551318 4.88 2624.01 6 6 3133012 2.02 1088.69 7 7 1995046 1.29 693.26 8 8 823995 0.53 286.33 9 9 204940 0.13 71.21 10 10 14803470 9.56 5144.06MIN is the minimum value (1 at the least)
Statistics Summary Table, SOILSGW.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 list condgw.sta Record MIN MAX MEAN STDV 1 1.000 10.000 2.478 2.842
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.
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://pubsdata.usgs.gov/pubs/of/2001/0486/index.html
Page Contact Information: GS Pubs Web Contact
Page Last Modified: Friday, 04-Nov-2022 15:04:43 EDT
