Tools for evaluating aquatic resource condition

Wetland Prioritization Study Main Page

 

Single-objective tools

 

Multi-objective tools

 

CNHP Landscape Integrity Model:1 The Colorado Nautral Heritage Program's LIM ranks wetlands in terms of their "overall landscape integrity," an indicator of the overall stress on each wetland derived by combining four stressor categories comprising 13 total stressors. Each stressor was modeled based on a single landscape feature that served as an indicator of stress on surrounding wetlands and was derived from readily-available GIS data. CNHP assigned a weight to each stressor based on the best professaionl judgment of the LIM team and modeled the decline in the effect of each stressor, or lack thereof, across space using the distance-decay function described by the equation below.

 

 

Using the distance-decay curve, the team had the ability to describe the effect of stressors in a variety of ways, ranging from having a high impact (i.e., high weight) but declining rapidly with distance to having a low impact (i.e., low weight) but decaying gradually. Within buffer regions surrounding each wetland, CNHP used these stressor maps to calculate landscape integrity scores.

A distance-decay function was not used, however, to describe the effects of Tamarisk populations and hydrologic modification. Tamarisk effects were described simply in terms of the footprint of Tamarisk distributions. Effects of hydrologic modifications, which accumulate with the water flow downstream rather than propagating equally in all directions, were described using TNC's method for calculating hydrologic disturbance downstream.

CNHP and partners will use the final output map resulting from this process to prioritize wetland protection, restoration, and enhancement efforts. For example, a wetland may be determined to be a good candidate for protection if it is determined to have high landscape integrity (low stress). On the other hand, if a wetland has low landscape integrity (high stress), but is restorable within its natural range of variation, it may represent a good candidate for restoration. A wetland may be a good candidate for enhancement if it has low landscape integrity (high stress) and cannot be restored to within its natural range of variation, but can be enhanced for specific ecological functions.

 

Factor used in analysis

Data source

Land use and development

Industrial/urban development

LandFire current vegetation: high and medium intensity development

Suburban/rural development

LandFire current vegetation: low intensity develoment

Highly modified open space

LandFire current vegetation: developed open space

Primary roads (interstate highways)

US Census TIGER/Line: primary roads

Secondary roads (state highways)

US Census TIGER/Line: secondary roads

Local and primitive roads

US Census TIGER/Line: local/primitive roads

Agriculture

LandFire current vegetation: pasture/hay and cultivated/irrigated

Energy development and resource extraction

Active oil and gas wells

Colorado Oil and Gas Conservation Commission: active wells

Inactive oil and gas wells

Colorado Oil and Gas Conservation Commission: plugged/abandoned wells

Wind turbines

CNHP

Active sand and gravel mines

Colorado Division of Mine Safety: active sand and gravel mines

Other active and abandoned mines

Colorado Division of Mine Safety: all other active mines

Hydrologic modification

Reservoir storage as proportion of mean annual flow

TNC Freshwater Measures Database

Water use as a proportion of mean annual flow

TNC Freshwater Measures Database

Dams and diversions by stream length

TNC Freshwater Measures Database

Groundwater wells

Colorado Division of Water Resources: active groundwater wells

Weed infestations

Tamarisk populations

The Tamarisk Coalition and TNC

 Acronym definitions

 

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CNHP Wetland Profile:1 CNHP has completed wetland profiles for each of Colorado's ten major river basins by summarizing information about the extent and distribution of wetlands within each. Using various classification systems to group wetland types into "bundles" of wetlands sharing similar ecological functions, CNHP is able to obtain information about the abundance and location of wetland functions throughout river basins. For example, profiles obtained for depressional wetlands enable CNHP to make inferences about the status and trends of wetland-dependent wildlife species, such as waterbirds and amphibians, which often depend on habitat provided by depressional wetlands.

 

Factor used in analysis

Data source

Existing wetlands

NWI

Wetland condition

Landscape integrity model outputs

 Acronym definitions

 

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EPA RPS Stressor Exposure Tool:2This tool evaluates ecological condition in terms of stressors and their sources for a set of hydrologic units based on a variety of indicators. The results are comparative within the population of units being assessed. By assessing subwatershed units within HUC-8s, for example, the tool identifies areas that might be targeted for restoration either based on their own restorability alone, or to achieve the largest improvement in condition for the HUC-8 as a whole.

Whereas the simplest form of screening often provides useful insights about general differences in restorability, further analysis of results is possible by evaluating more homogeneous subsets of the full population of waters or watersheds being compared. For example, users of the EPA RPS Stressor Exposure Tool may target pathogen-impaired watersheds, identified as those watersheds for which ecological, stressor, and social indicators that best address pathogen impairment and recovery factors are present. As another example, users of the EPA RPS might target urban watersheds separately from agricultural watersheds. In selecting indicators, EPA RPS eliminates those that are redundant or highly correlated by using statistical analysis to evaluate the similarity between indicator datasets.

 

Factor used in analysis

Data source(s)

Watershed-level disturbance

Watershed percent agriculture

NLCD 1992(4); NLCD 2001(5); NLCD 2006(6); various state sources for land cover data; USGS cropland data by county(7); NHDplus catchments(4); USDA national GIS crop dataset(8); BLM dataset on range allotments and pastures(9)

Watershed percent steep slope agriculture

NLCD 1992(3); NLCD 2001(4); NLCD 2006(5); various state source for land cover data; USGS cropland data(7); USGS NED(6); USGS EDNA(7); NHDplus flowline elevation data(4)

Watershed number of CAFOs

State records mapping CAFO locations and livestock species and numbers

Watershed number of septic systems (zones of potential septic usage and assumed partial failure rates)

Non-sewered area maps; municipality-level individual septic records; septic failure rate coefficient from watershed studies and TMDLs

Watershed percent impervious cover

NLCD 2001(4); NLCD 2006(5); NHDplus catchments(4)

Watershed percent tile-drained cropland

State-level digital soil survey data; NRCS Soil Data Mart(8); NLCD 1992(3); NLCD 2001(4); NLCD 2006(5); various state sources of land cover data; USGS cropland by county(6); USDA national GIS crop dataset(7)

Watershed percent U index (percent anthropogenic cover types)

NLCD(2); statewide land cover data from state-specific sources

Watershed percent urban

NLCD(2); statewide land cover data from state-specific sources

Watershed road density (mean road length per watershed square mile)

Transportation GIS datasets; national road and stream data from the National Atlas(10); ESRI roads dataset(11)

Other percent watershed stressor (e.g., surface mining for some watersheds)

Dependent upon additional stressors identified

Corridor and shoreland disturbance

Corridor percent impervious cover

NLCD 2001(4) and 2006(5) data for impervious and urban land cover; NHDplus catchments(4)

Corridor percent tile-drained cropland

State-level digital soil survey data; NRCS Soil Data Mart(8); NLCD 1992(3); NLCD 2001(4); NLCD 2006(5); various state sources of land cover data; USGS cropland by county(6); USDA national GIS crop dataset(7)

Corridor percent U-index (percent anthropogenic land cover types)

NLCD(2); statewide land cover data from state-specific sources

Corridor percent urban

NLCD(2); statewide land cover data from state-specific sources

Corridor percent agriculture

NLCD 1992, NLCD 2001; NLCD 2006; various state sources for land cover data; USGS cropland by county(6); USDA national GIS crop dataset7; BLM data on range allotments and pastures(8)

Linear percent of channel through agriculture (percent total stream length through agricultural land use or percent agricultural area adjacent to stream)

Stream hydrography data; land cover data

Corridor road crossings

National road and stream data from the National Atlas(9); Landsat data for roads and stream from USGS Earth Explorer(12); ESRI roads dataset(10); data for unimproved road crossings in remote parts of federal lands from land management agency

Corridor road density

National road and stream data from the National Atlas(9); ESRI roads dataset(10)

Hydrologic alteration

Aquatic barriers (count per watershed or relative isolation of specific stream segment of similar Strahler order)

Aquatic barriers to fish passage from the USFWS Decision Support System(13); major dams mapping by the USACE National Inventory of Dams(14); NHD data on dams and divergence structures(6)

Channelization (percent of total impaired stream length artificially straightened)

USGS NHD(6); local resources; channelization attribute data for 303(d) listed streams included in EPA ATTAINS data system(20)

Hydrologic alteration (scores waterbody segments downstream of dams or withdrawals based on dam size, active status, role on flow alteration and feasibility of flow management)

Aquatic barriers to fish passage from the USFWS FPDSS(12); major dams mapping by the USACE National Inventory of Dams(13); NHD data on dams and divergence structures(6); State data on water withdrawal locations (e.g. Michigan15)

Relative net water demand

Gauging station records, which may be used to develop natural flow estimators and calculate water demand relative to natural flow

Water use intensity

Gauging station records, which may be used to develop natural flow estimators and calculate water demand relative to natural flow

Biotic or climatic risks

Elevation (mean elevation of the watershed or specific stream segment)

USGS NED(6); USGS EDNA(7); NHDplus flowline elevation data(4)

Invasive species risk

USGS Non-Indigenous Aquatic Species Information Resource(16); Non-Indigenous Species Database Network range maps(17); USDA National Invasive Species Information Center(18)

Severity of pollutant loading

Number of 303(d) listed causes

ATTAINS(20)

Number of permits

EPA's national geospatial dataset on permits

CSO or MS4 areas

Spatial data available at state and municipal level

Age of sewer infrastructure

Spatial data available at municipal level

Severity of loading (compares current loading with TMDL target loading calculation for percent reduction needed)

ATTAINS data on 303(d)-listed waters(20); loading estimates from TMDLs or watershed models (e.g., from EPA's website)(19)

Stressor persistence

Project specific

SPARROW nitrogen loading estimate

Water quality data from EPA's NPDAT website(20); regional modeling data from the USGS decision support system(21)

SPARROW phosphorus loading estimate

Water quality data from EPA's NPDAT website(19); regional modeling data from the USGS decision support system(20)

Watershed stream miles impaired

EPA ATTAINS data on 303(d)-listed waters(20)

Watershed water body acres impaired

EPA ATTAINS data on 303(d)-listed waters(20)

Modeled watershed aerial N deposition

N/A

Modeled watershed aerial Hg deposition

REMSAD; CMAQ; range of likely impacts from foreign sources(22)

Other stressor-specific severity factors

Project-specific stressor data

Legacy of past, trajectory of future use

Land use change trajectory

NLCD 1992(3); NLCD 2001(4); NLCD 2006(5); USGS Land Cover Trends Project(23); USGS Temporal Urban Mapping project(24); USGS Historical Topographic Map Collection(25)

Legacy land uses

USGS Land Cover Institute(26); NLCD 1992(27); NLCD land use change between 2001 and 2006(3); Historical Topographic Map Collection(24_

Watershed percent legacy agriculture

USGS Land Cover Institute(25); NLCD 1992(26); NLCD land use change between 2001 and 2006(3)

Watershed percent legacy urban

USGS Land Cover Institute(26); NLCD 1992(27); NLCD land use change between 2001 and 2006(3); Historical Topographic Map Collection(24)

Corridor percent legacy agriculture

USGS Land Cover Institute(25); NLCD 1992(26); NLCD land use change between 2001 and 2006(3)

Corridor percent legacy urban

USGS Land Cover Institute(26); NLCD 1992(27); NLCD land use change between 2001 and 2006(3); Historical Topographic Map Collection(24)

 Acronym definitions

 

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IDFG Watershed Condition Tool:28 IDFG ranked individual HUC-12 watersheds using an analysis for which metrics were selected based on the literature review and professional judgment alone. Because watershed reference data were unavailable, no field-based calibration of metrics was completed, as was done for IDFG's wetland condition tool. IDFG summed all metrics and ranked each HUC-12 in terms of six condition classes ranging from "minimally disturbed" (rank = 1) to "completely disturbed" (rank = 6).

 

Factor used in analysis

Data source(s)

ATtILA Landscape metrics

Total terrestrial area

NLCD(29)

Percent cropland

Percent pasture

Percent all agricultural land use

Percent forest

Percent man-made barren

Percent natural barren

Percent natural grassland

Percent shrubland

Percent urban

Percent user-defined class

Percent wetland

Percent all natural land use

Percent all human land use

Percent agricultural cropland on slopes › 10%

NLCD(27); NED

Percent agricultural pasture on slopes › 10%

Percent any agricultural on slopes › 10%

ATtILA Riparian metrics

Percent stream length adjacent to agricultural land use

NLCD(27); NED

Percent stream length within 30m of agricultural land use

Percent stream length wthin 120m of agricultural land use

Percent stream length adjacent to cropland

Percent stream length within 30m of cropland

Percent stream length within 120m of cropland

Percent stream length adjacent to pasture

Percent stream length within 30m of pasture

Percent stream length within 120m of pasture

Percent stream length adjacent to urban land use

Percent stream length within 30m of urban land use

Percent stream length within 120m of urban land use

Percent stream length adjacent to human land use

Percent stream length within 30m of human land use

Percent stream length within 120m of human land use

Percent stream length adjacent to natural grassland

Percent stream length within 30m of natural grassland

Percent stream length within 120m of natural grassland

ATtILA Human stressor metrics

Density of 4-lane highways

TIGER 2000 (1:100,000)(28)

Density of 2-lane highways

Density of interstate freeways

Length of roads within 30m of streams

TIGER 2000 (1:100,000)(30); NHD

Length of 4-lane highways within 30m of streams

Length of 2-lane highways within 30m of streams

Length of county, city roads within 30m of streams

Number of road/stream crossings

Number of 4-lane highway/stream crossings

Number of 2-lane highway/stream crossings

Number of county, city road/stream crossings

Nutrient loading

N/A

Phosphorus loading

N/A

Population density (population count/km 2)

N/A

Percent change in total population

N/A

Percent impervious cover

NLCD(27)

ATtILA physical characteristic metrics

Area of wetland

NWI

Stream density

NHD

Topographic position of wetland

NED

Desktop GIS-derived metrics

Density of canals, ditches (km/km 2)

NHD

Density of wells (#/km 2)

N/A

Percent of land likely grazed by livestock

NLCD(27); BLM; ICBEMP

Pollutant discharge

EPA; ICBEMP

Railroads

TIGER 2000 (1:100,000)(28)

Recreation access and navigation improvements

BLM; IDPR

Recent timber harvest

USGS; Northwest ReGAP project; NatureServe

Toxic element concentration

EPA; ICBEMP

Utility corridors

ICBEMP

Dairies

IDWR

Dams and reservoirs

IDWR; NHD

Dredge spoils or other solid waste disposal

EPA

Effluent discharge (from industrial or energy facility that alters thermal regime)

EPA

Groundwater pumping: ex-urban development

IDWR

Mining

IDL; USGS; IDEQ

 

Acronym definitions

 

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IDFG Wetland Condition Tool:28 For each wetland polygon in its north and south study sites, IDFG combined metrics found to be most predictive of wetland condition with an "index of environmental vulnerability" to assign each wetland one of four condition classes ranging from minimally disturbed (rank = 1) to completely disturbed (rank = 4).

 

Factor used in analysis

Data source(s)

North region

Percent agricultural land use

NLCD(27)

Percent natural grassland

Percent cropland

Percent pasture

Percent urban

Percent stream length within 30m of urban land use

NHD; NLCD(27)

Percent stream length within 30m of urban land use

Percent agricultural land use on slopes › 9%

NLCD(27); NED

Density of 4-lane highways

TIGER 2000 (1:100,000)(28)

Density of 2-lane highways

Length of 4-lane highways within 30m of streams

TIGER 2000 (1:100,000)(28); NHD

Length of 2-lane highways within 30m of streams

Number of 4-lane highway/stream crossings

Number of 2-lane highway/stream crossings

Nitrogen loading

N/A

Phosphorus loading

N/A

Population density

N/A

Density of wells (#/km 2)

N/A

Percent likely grazed by livestock

NLCD; BLM; ICBEMP

Index of environmental vulnerability

Mean elevation

NED (30m)

Mean precipitation

UM NTSG total precipitation data (1980-1997, 18-year mean, 1 km resolution)(31)

Mean slope

NED (30m)

Percent forest

2001 NLCD

Percent stream length adjacent to natural land

Streamnet (IDFG 2008, 1:100,000)

Percent stream length within 30m of natural land

Streamnet (IDFG 2008, 1:100,000)

South region

Percent agricultural land use

NLCD(27)

Percent cropland

Percent pasture

Percent urban

Percent human land use

Percent stream length adjacent to agricultural land use

NLCD(27); NHD

Percent stream length within 30m of agricultural land use

Percent stream length within 120m of agricultural land use

Percent stream length adjacent to cropland

Percent stream length within 30m of cropland

Percent stream length within 120m of cropland

Percent stream length adjacent to pasture

Percent stream length within 30m of pasture

Percent stream length within 120m of pasture

Percent stream length adjacent to pasture

Percent stream length adjacent to urban land use

Percent stream length within 30m of urban land use

Percent stream length within 120m of urban land use

Percent stream length adjacent to human land use

Percent stream length within 30m of human land use

Percent stream length within 120m of human land use

Percent stream length adjacent to natural grassland

Percent stream length within 30m of natural grassland

Percent stream length within 120m of natural grassland

Density of interstate freeways

TIGER 2000 (1:100,000)(28)

Length of roads within 30m streams

TIGER 2000 (1:100,000)(28); NHD

Length of county, city roads within 30m of streams

Number of road/stream crossings

Number of county, city road/stream crossings

Nitrogen loading

N/A

Phosphorus loading

N/A

Area of wetland

NWI

Stream density

NHD

Density of canals, ditches (km/km 2)

NHD

Density of wells (#/km 2)

N/A

Percent likely grazed by livestock

BLM; ICBEMP; NLCD(27)

Index of environmental vulnerability

Mean elevation

NED (30m)

Mean precipitation

UM NTSG total precipitation data (1980-1997, 18-year mean, 1 km resolution)

Mean slope

NED (30m)

Area of wetland

NWI

Stream density

Streamnet (IDFG 2008, 1:100,000)

 Acronym definitions

 

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MTNHP Landscape Integrity Model:32 MTNHP built the LIM using input factors derived from an analysis that determined landscape predictors of wetland condition in addition to metrics for landscape-level stressors shown by the scientific literature to have important impacts on wetland condition. Final metrics comprised four categories - roads, land cover, hydrology, and resource extraction, each of which was made up of individual component layers representing human change to the landscape (e.g., "highways" in the "roads" category). To each component layer, the MTNHP researchers applied an inverse-weighted distance function that assigned a score to each 30m 2 pixel surrounding the wetland that reflected the decrease in magnitude of each impact with distance across the landscape. These individual component layers, scored for impacts, were weighted and summed into overall category rasters, which were in turn weighted and summed to obtain final MTLIM scores.

 

Factor used in analysis

Data source(s)

Roads

4-wheel drive

2001 TIGER/US Census Bureau

Local roads, city streets

Highways

Land cover

Urban

2001 NLCD

Crop agriculture

Timber harvest

Hydrology

Artificial flow

2007 NHD

Water rights point-of-use

MTDNRC

Section 404 permits

MTNRIS

Resource extraction

Abandoned mines

MTDEQ

Oil or gas extraction

MTNRIS

 Acronym definitions

 

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TNC Aquatic Ecoregional Assessment Aquatic System Integrity GIS model: To develop its portfolio of priority sites, TNC first applied a GIS screening analysis to rank river systems based on landscape variables known to correlate with the biological integrity of aquatic communities. These variables were grouped into three categories: land cover and road impacts (impacts due to roads, urbanization, and agriculture), dam and drinking water supply impacts (impacts caused by altered hydrologic regimes and creation of migration barriers), and point source impacts (potential chemical or nutrient threats due to point sources). By ranking each target river system for each category, TNC was able to identify those river systems that were most intact within each ecological draining unit (EDU).

 

Factor in the analysis

Data source(s)

Land cover and road impacts

Percent developed land

National Land Cover Dataset

Road density

StreetMap USA (Esri & Tele Atlas)

Density of road/stream crossings

StreetMap USA and National Hydrography Dataset

Dam and drinking water supply impacts

Dam density

EPA

Dam storage capacity

EPA

Drinking water supply density

EPA

Point source impacts

Point source density

EPA

 Acronym definitions

 

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TNC Aquatic Ecoregional Assessment Landscape context GIS model:34 TNC obtained "landscape context" rankings for each watershed by calculating the percent coverage of each watershed by three spatial variables: percent developed land, percent agricultural land, and total road density per watershed area. TNC applied the criteria listed in the table below to each of these three percentages, using the highest rank obtained among them to represent each watershed's ranking for overall landscape context.

 

 

Factor in the analysis

Data source

Percent developed land

NLCD

Percent agricultural land

NLCD

Total road density per watershed area

StreetMap USA

 Acronym definitions

 

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VIMS Wetland Condition Assessment Tool:34 This tool scored palustrine emergent, scrub/shrub, and forested wetlands within buffer regions surrounding each wetland based on the habitat and water quality stressors associated with surrounding land use types.

 

Factor used in analysis

Data source

Watersheds around each wetland

USGS National Elevation Dataset

Wetlands

NWI

Density of roads within 200m of each wetland

US Census TIGER/Line roads (2000)

Land cover data

NLCD

 Acronym definitions

 

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Weller et al. (2007) Landscape (Riverine Wetlands) Tool:35 This landscape assessment predicted the habitat condition Functional Capacity Index (FCI) score for riverine wetlands, which was calculated based on field data for condition of buffers 0-20m from wetland, condition of buffers 20-100m from wetland, and stream condition outside assessment area. This tool predicted FCI scores by inputting 30m resolution spatial metrics for stream proximity, road proximity, nearest stream condition, and surrounding land cover composition into a GIS-based model.

 

Factor used in analysis

Data source(s)

Condition of nearest stream (0 = excavated, 1 = natural)

NWI stream and ditch map

Percent cropland and grassland within 100m

2001 NWI

Percent developed land within 1000m

2001 NWI

Percent mixed forest within 1000m

2001 NWI

Distance to nearest stream (m)

1:24,000 NHD

Percent pixels with zero impervious cover within 100m

2001 NLCD

Distance to nearest road (m)

Census TIGER data(36)

Percent wetland within 100m

Wetlands from NWI and states of MD and DE

Percent forest within 100m

2001 NLCD

Percent wooded wetland within 1000m

2001 NLCD

 Acronym definitions

 

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Wetland Prioritization Study Main Page

 


1Colorado Natural Heritage Program. 2011. Statewide Strategies to Improve Effectiveness in Protecting and Restoring Colorado's Wetland Resource.
2 Webinar: "Recovery Potential Screening: A tool for comparing impaired waters restorability" by Doug Norton and Tatyana DiMascio. Accessed from: http://water.epa.gov/learn/training/wacademy/upload/2012_02_22_slides.pdf.
3US Environmental Protection Agency. Office of Water. Recovery Potential Stressor Indicators. Accessible from: http://owpubauthor.epa.gov/lawsregs/lawsguidance/cwa/tmdl/recovery/indicatorsstressor.cfm.
4
US Environmental Protection Agency. 1992 National Land Cover Data. Accessible from: http://www.epa.gov/mrlc/nlcd.html.
5
US Environmental Protection Agency. 2001 National Land Cover Data. Accessible from: http://www.epa.gov/mrlc/nlcd-2001.html.
6
Multi-resolution Land Characteristics Consortium. National Land Cover Database 2006. Accessible from: http://www.mrlc.gov/nlcd06_data.php.
7
The USGS Land Cover Institute. Cropland by County Since 1850 and Population Since 1790. Accessible from: http://landcover.usgs.gov/cropland/index.php.
8
US Department of Agriculture Natural Resources Conservation Service. Geospatial Data Gateway. http://datagateway.nrcs.usda.gov/GDGHome.aspx.
9
Department of the Interior Bureau of Land Management. GeoCommunicator. Accessible from: http://www.geocommunicator.gov/GeoComm/.
10
US Department of the Interior. National Atlas. Accessible from: http://nationalatlas.gov/.
11
ArcGIS. Updated May 2013. World Street Map. Accessible from: http://www.arcgis.com/home/item.html?id=3b93337983e9436f8db950e38a8629af.
12
US Geological Survey. Earth Explorer. Accessible from: http://earthexplorer.usgs.gov/ .
13
US Fish and Wildlife Service. GeoFin Geospatial Fisheries Information Network. Accessible from: http://edcsns17.cr.usgs.gov .
14
US Army Corps of Engineers. National Inventory of Dams. Accessible from: http://geo.usace.army.mil/pgis/f?p=397:12
15
State of Michigan Department of Environmental Quality. Water Withdrawal Reports, Data and Graphics. Accessible from: http://michigan.gov/deq/0,1607,7-135-3313_3677_3704-72931--,00.html .
16
US Geological Survey. Nonindigenous Aquatic Species. Accessible from http://nas.er.usgs.gov/default.aspx .
17
Steves, B. P. 2003. An International Nonindigenous Species Database Network. Smithsonian Environmental Research Center. Accessible from: http://www.nisbase.org/nisbase/index.jsp .
18
US Department of Agriculture National Agricultural Library. Resource Library Databases. Accessible from: http://www.invasivespeciesinfo.gov/resources/databases.shtml .
19
US Environmental Protection Agency. AskWaters. Accessible from: http://iaspub.epa.gov/pls/waters/f?p=ASKWATERS:EXPERT:0
20
US Environmental Protection Agency. Nitrogen and Phosphorus Pollution Data Access Tool . Accessible from: http://www2.epa.gov/nutrient-policy-data/nitrogen-and-phosphorus-pollution-data-access-tool .
21
US Geological Survey. SPARROW Decision Support System. Accessible from: http://cida.usgs.gov/sparrow/ .
22
US Environmental Protection Agency. Total Maximum Daily Loads Technical Support Documents. Accessible from: http://water.epa.gov/lawsregs/lawsguidance/cwa/tmdl/techsupp.cfm .
23
US Geological Survey. Land Cover Trends Project Download Overview. Accessible from: http://landcovertrends.usgs.gov/download/overview.html.
24
US Geological Survey Land Cover Institute. Urban Dynamics: Temporal Urban Mapping. Accessible from: http://landcover.usgs.gov/urban/umap/.
25
US Geological Survey. The National Map: Historical Topographic Map Collection. http://nationalmap.gov/historical/.
26
The USGS Land Cover Institute. Cropland by County Since 1850 and Population Since 1790. Accessible from: http://landcover.usgs.gov/cropland/index.php.
27
US Geological Survey Land Cover Institute. National Land Cover Dataset 1992. Accessible from: http://landcover.usgs.gov/natllandcover.php.
28
Idaho Department of Fish and Game. 2010. Development of a landscape-scale wetland condition assessment tool for Idaho.
29 NLCD data are available from: http://www.mrlc.gov/nlcd2001.php
30
TIGER roads/railroads data available from: http://www.census.gov/geo/maps-data/data/tiger.html
31
UM NTSG precipitation data available from: http://www.ntsg.umt.edu/project/daymet
32
Vance LK. 2009. Assessing Wetland Condition with GIS: A Landscape Integrity Model for Montana. A Report to The Montana Department of Environmental Quality and The Environmental Protection Agency. Montana Natural Heritage Program, Helena, MT. 23 pp. plus appendices.
33 The Nature Conservancy. 2009. The Nature Conservancy's watershed approach to compensation planning for the Virginia Aquatic Resource Trust Fund.
34 Center for Coastal Resources Management, Virginia Institute of Marine Science, College of William and Mary. 2007. Development of a nontidal inventory and monitoring strategy for Virginia - completion of phase II (coastal plain and piedmont physiographic provinces): Final report to the Environmental Protection Agency Region III.
35 Center for Coastal Resources Management, Virginia Institute of Marine Science, College of William and Mary. 2007. Development of a nontidal inventory and monitoring strategy for Virginia - completion of phase II (coastal plain and piedmont physiographic provinces): Final report to the Environmental Protection Agency Region III.
36 US Department of Commerce US Census Bureau. Maps and Data TIGER Products. Accessible from: http://www.census.gov/geo/maps-data/data/tiger.html.