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Water: Recovery Potential

Stressor Indicators

Stressor Indicators

This web page contains stressor indicators for recovery potential, their relevance to recovery, and basic information about data sources and measurement. Click on each indicator name for indicator-specific fact sheets with more information, including literature excerpts.

Watershed-level disturbance

watershed % agriculture (PDF) (9 pp, 90.3K, About PDF)

Why relevant to recovery: Croplands and pastures have been linked to a wide variety of water quality and biotic impacts on waters. Common effects seen at moderate to high agricultural proportions of total watershed land cover include less diverse and more intolerant macrobenthic communities, increased nutrient loading resulting in turbid water, overall homogenization of the fish fauna, accelerated erosion and bank destabilization, suspended sediment particles carrying pesticides, pathogens, and heavy metals, habitat degradation and reduced biodiversity, and increases in specific conductivity, DIN, DRP, and TP concentrations. See other highlights in literature excerpts, below. Although watershed agriculture is commonly linked to degraded aquatic conditions that may be difficult to reverse and quite persistent over time, it is important to note that some degree of recovery is rarely considered impossible.

Data sources and measurement: Calculated as % by area within watershed; often cropland and pasture are compiled as separate metrics. Land cover sources include the National Land Cover Data from 1992 (See: http://www.epa.gov/mrlc/nlcd.html Exit EPA Disclaimer), 2001 (See: http://www.epa.gov/mrlc/nlcd-2001.html Exit EPA Disclaimer), and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer) as well as various state sources. The USGS lists cropland by county since 1850 (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). Approximate watershed boundaries can be constructed by aggregating small-scale catchments from the NHDplus datasets (See:  Exit EPA Disclaimer). If the user chooses to use this indicator for a specific crop relevant to the study area, USDA has developed a national GIS crop dataset that can be downloaded from Geospatial Data Gateway (See: http://datagateway.nrcs.usda.gov/GDGHome.aspx Exit EPA Disclaimer). In addition, where applicable, BLM data set on range allotments and pastures can be used (See: http://www.geocommunicator.gov/GeoComm/ Exit EPA Disclaimer).

 

watershed % steep slope agriculture

Why relevant to recovery: See watershed % agriculture for rationale.  Specifically on steep slopes, cropland is associated with higher erosion and overland transport of nutrients and other pollutants.  Abundant steep-slope agriculture in a watershed may represent a significant difficulty to overcome in restoration efforts.

Data sources and measurement: Calculated as % by area within watershed; land cover data and elevation data (preferably converted to slope map categories) are necessary to target the steep slope agriculture. Land cover sources include the National Land Cover Data from 1992 (See: http://www.epa.gov/mrlc/nlcd.html), 2001 (See: http://www.epa.gov/mrlc/nlcd-2001.html), and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer) as well as various state sources. If the user chooses to use this indicator for a specific crop relevant to the study area, USDA has developed a national GIS crop dataset that can be downloaded from Geospatial Data Gateway (See: http://datagateway.nrcs.usda.gov/GDGHome.aspx Exit EPA Disclaimer). The National Elevation Dataset (NED) (See: http://nhd.usgs.gov/index.html Exit EPA Disclaimer) is adequate for generalized differences in elevation. High resolution elevation data should be used for any assessment units at HUC12 level of smaller.  The Elevation Derivatives for National Applications (EDNA) has been derived from the NED and is hydrologically conditioned to improve hydrologic flow representation (see: http://edna.usgs.gov/ Exit EPA Disclaimer).  NHD plus contains information on maximum and minimum elevation for each flowline (http://www.horizon-systems.com/nhdplus/ Exit EPA Disclaimer).

 

watershed number of CAFOs

Why relevant to recovery: Confined animal feeding operations (CAFOs) are a spatially concentrated source of nutrients and pathogens that, although frequently managed or regulated, can episodically release pollutants that set back impaired waters recovery. Due to the high magnitude of pollutant loads associated with CAFOs, they can be considered a potential stressor that may reduce recovery potential in some areas.

Data sources and measurement: State records may identify or map CAFO locations and likely also the livestock species and numbers.

 

watershed number of septic systems

Why relevant to recovery: Although subject to regulations, private septic systems are in failure frequently enough that many watershed models routinely assume a "% septic failure" factor of 30%.  or more. Failed septics that reach waterways can increase nutrient and pathogen loadings, as well as deliver household toxins such as chlorine. Because of difficulty of detection, failed septic systems are also an obstacle to effective recovery and restoration targeting.

Data sources and measurement: Land cover maps overlaid with non-sewered area maps can help identify zones of potential septic usage and assumed partial failure rates. Some municipalities have individual septic records that can be summed by township or watershed. Local watershed studies and TMDLs may provide a source for septic failure coefficient assumed in the area.

 

watershed % impervious cover (PDF) (8 pp, 103K, About PDF)

Why relevant to recovery: Impervious cover is an indicator of the impacts of urbanization and development on water resources. Impervious cover results in multiple stressors to a watershed, such as increased pollutant loads from stormwater runoff, altered stream flow, decreased bank stability, and increased water temperatures. The significance of this metric in reducing recovery potential is based on the multiple impacts to the watershed as well as the nearly irreversible nature of imperviousness at high levels.

Data sources and measurement: Multiply the watershed area classified as "urban" (i.e. low, medium, and high density residential; commercial; industrial; etc) by the appropriate impervious cover coefficient for each land use type. The percent impervious cover indicator is calculated by averaging the impervious cover areas across the total land area of the watershed. If possible, differentiating between impervious cover contiguous with or isolated from drainage should be done to estimate 'effective' impervious cover.  The 2001 and 2006 National Land Cover Data contains information on impervious covers as well as urban land cover (See: http://www.epa.gov/mrlc/nlcd-2001.html and http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer). Approximate watershed boundaries can be constructed by aggregating small-scale catchments from the NHDplus datasets (See: http://www.horizon-systems.com/nhdplus/ Exit EPA Disclaimer).

 

watershed % tile-drained cropland (PDF) (3 pp, 51.9K, About PDF)

Why relevant to recovery: Tiles efficiently drain water from the soil saturated zones to streams, thereby reducing residence time in areas conducive to denitrification and increasing nitrogen export. Tile draining also has created concern for the delivery of sediment, sources of bacteria, contaminants, and suspended solids. Tile drains can selectively transport fine-grained sediment from soils to receiving freshwater, increase the size of the contributing area by hydraulically connecting remote areas of the catchment to the stream system, and circumvent management strategies such as buffer strips. Subsurface drain tiling that accompanies wetland drainage can lead to flashy hydrology that can decimate the stream biota. Most of the above effects are exacerbated by the way tiles extend the total area producing these negative impacts farther out into the watershed.

Data sources and measurement: Based on verifying the association of tile drain usage with specific hydric soil types that are being cropped. Basic information needs include three elements: locally gathered monitoring data on agricultural practices associated with specific hydric soil types and agricultural uses (e.g., NASS, NRI surveys by USDA), soil type mapping, and agricultural land cover mapping). Digital soil survey data varies from State to State in availability. States with fully digitized county soil survey-level information can use this metric most effectively. Physical and chemical properties of soils are available for most areas as part of the US General Soils Map through the NRCS Soil Data Mart (See: http://soildatamart.nrcs.usda.gov/ Exit EPA Disclaimer). Land cover sources include the National Land Cover Data from 1992 (See: http://www.epa.gov/mrlc/nlcd.html), 2001 (See: http://www.epa.gov/mrlc/nlcd-2001.html), and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer), as well as various state sources. The USGS lists cropland by county since 1850 (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). If the user chooses to use this indicator for a specific crop relevant to the study area, USDA has developed a national GIS crop dataset that can be downloaded from Geospatial Data Gateway (See: http://datagateway.nrcs.usda.gov/GDGHome.aspx Exit EPA Disclaimer).

 

watershed % U index (PDF) (2 pp, 33.4K, About PDF)

Why relevant to recovery: Watershed-wide U-index (anthropogenic) land cover patterns are associated with benthic macroinvertebrate communities that are tolerant of stream degradation, indicating a lower level of aquatic ecological integrity and water quality. As the intensity of human activities increase there is a tendency that the biological integrity of the rivers decreases. Increasing substrate embeddedness and bank erosion have also been observed to increase in streams in developing areas. High U-index may indicate that, as widespread anthropogenic cover is unlikely to be reduced and is complex to remediate, U-index may be a strong determinant of poor recovery prospects.

Data sources and measurement: Extracted from land cover mapping within the watershed, and summarized as % anthropogenic cover types (e.g. developed, agricultural) by area. For land cover data, the National Land Cover Database (NLCD) for 2006, 2001 and 1992 is accessible at http://www.mrlc.gov/finddata.php Exit EPA Disclaimer; numerous statewide land cover mapping datasets are also available from state-specific sources.

 

watershed % urban (PDF) (30 pp, 311K, About PDF)

Why relevant to recovery: Urbanization of a watershed results in multiple stressors to a watershed, such as increased pollutant loads from stormwater runoff, altered stream flow, decreased bank stability, and increased water temperatures. The significance of this metric in reducing recovery potential is based on the multiple impacts to the watershed as well as the nearly irreversible nature of imperviousness. (See also Watershed Impervious Cover under Stressor Exposure indicators.)

Data sources and measurement: Measured as a percent of the area of a watershed with a land use classification of "urban" (i.e. low, medium, and high density residential; commercial; industrial; etc). For land cover data, the National Land Cover Database (NLCD) for 2006, 2001 and 1992 is accessible at http://www.mrlc.gov/finddata.php Exit EPA Disclaimer; numerous statewide land cover mapping datasets are also available from state-specific sources.

 

watershed road density (PDF) (3 pp, 57.6K, About PDF)

Why relevant to recovery: Storm drains and roads appeared to be important elements influencing the degradation of water quality with respect to the biota. Fish density, number of intolerant fish species, and invertebrate density are seen to change in association with more roads in watersheds. Studies of Middle Atlantic streams have linked greater road densities to increased conductivity and subsequent impacts on aquatic life. Roads also add to impervious cover and thereby contribute to many secondary effects on flashy flows and related destabilized channels, increased urban pollutant transport, and other effects.

Data sources and measurement: Mean road length per watershed square mile. Transportation GIS datasets are widely available and can be used in overlay with an impaired waters dataset where watershed boundaries have been delineated. National road and stream data is obtainable through the National Atlas (See: http://nationalatlas.gov/ Exit EPA Disclaimer). Transportation GIS datasets are widely available and can be used in overlay with an impaired waters dataset where watershed boundaries have been delineated. ESRI offers a free roads dataset that can be opened in ArcMap (http://www.arcgis.com/home/item.html?id=3b93337983e9436f8db950e38a8629af Exit EPA Disclaimer).

 

other % watershed stressor

Why relevant to recovery: The indicators described in this table are not an exhaustive list of all the stressors that might play a highly significant role in the restorability of some watersheds. Surface mining, for example, is not among the indicators summarized but can play a major role in comparison of recovery potential of some watersheds. This metric is a simple placeholder for regionally-significant stressors in watersheds that are not captured in other indicators.

Data sources and measurement: As appropriate, depending upon data source.

 

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Corridor and shorelands disturbance

corridor % impervious cover (PDF) (3 pp, 50.9K, About PDF)

Why relevant to recovery: Impervious cover is an indicator of the impacts of urbanization and development on water resources. Some literature reveals greater impacts of corridor urbanization and imperviousness than the same activities across the watershed. Impervious cover results in multiple stressors to a watershed, such as increased pollutant loads from stormwater runoff, altered stream flow, decreased bank stability, and increased water temperatures. The significance of this metric in reducing recovery potential is based on the multiple secondary impacts to the corridor and water body as well as the nearly irreversible nature of imperviousness. (See also Watershed Percent Impervious.)

Data sources and measurement: Multiply the area classified as "urban" (i.e. low, medium, and high density residential; commercial; industrial; etc) within a defined corridor width (e.g. 90 meters per side) by the appropriate impervious cover coefficient for each land use type. The percent impervious cover indicator is calculated by averaging the impervious cover areas across the total land area of the corridor. If possible, differentiating between impervious cover contiguous with or isolated from drainage should be done to estimate 'effective' impervious cover. The 2001 and 2006 National Land Cover Data contains information on impervious covers as well as urban land cover (See: http://www.epa.gov/mrlc/nlcd-2001.html Exit EPA Disclaimer and http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer). Approximate watershed boundaries can be constructed by aggregating small-scale catchments from the NHDplus datasets (See: http://www.horizon-systems.com/nhdplus/ Exit EPA Disclaimer).

 

corridor % tile-drained cropland

Why relevant to recovery: Tiles efficiently drain water from the soil saturated zones to streams, thereby reducing residence time in areas conducive to denitrification and increasing nitrogen export. Tile draining also has created concern for the delivery of sediment, sources of bacteria, contaminants, and suspended solids. Tile drains can selectively transport fine-grained sediment from soils to receiving freshwater, and increase the size of the contributing area, by hydraulically connecting remote areas of the catchment to the stream system, and (ii) circumvent management strategies such as buffer strips. Subsurface drain tiling that accompanied wetland drainage can lead to flashy hydrology that can decimate the stream biota.

Data sources and measurement: Based on verifying the association of tile drain usage with specific hydric soil types that are being cropped. Basic information needs include three elements: locally gathered monitoring data on agricultural practices associated with specific hydric soil types and agricultural uses (e.g., NASS, NRI surveys by USDA), soil type mapping, and agricultural land cover mapping). Digital soil survey data varies from State to State in availability. States with fully digitized county soil survey-level information can use this metric most effectively. Physical and chemical properties of soils are available for most areas as part of the US General Soils Map through the NRCS Soil Data Mart (See: http://soildatamart.nrcs.usda.gov/ Exit EPA Disclaimer). Land cover sources include the National Land Cover Data from 1992 (See: http://www.epa.gov/mrlc/nlcd.html), 2001 (See: http://www.epa.gov/mrlc/nlcd-2001.html), and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer), as well as various state sources. The USGS lists cropland by county since 1850 (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). If the user chooses to use this indicator for a specific crop relevant to the study area, USDA has developed a national GIS crop dataset that can be downloaded from Geospatial Data Gateway (See: http://datagateway.nrcs.usda.gov/GDGHome.aspx Exit EPA Disclaimer).

 

corridor % U-index  (PDF) (2 pp, 42.2K, About PDF)

Why relevant to recovery: Both riparian and watershed-wide U-index (anthropogenic) land cover patterns are associated with benthic macroinvertebrate communities that are tolerant of stream degradation, indicating a lower level of aquatic ecological integrity and water quality. As the intensity of human activities increase there is a tendency that the biological integrity of the rivers decreases. Increasing substrate embeddedness and bank erosion have also been observed to increase in streams in developing areas. High riparian U-index may indicate that, as widespread anthropogenic cover is unlikely to be reduced and is complex to remediate, U-index may be a strong determinant of poor recovery prospects.

Data sources and measurement: Extracted from land cover mapping within a set corridor width, and summarized as % anthropogenic cover types (e.g. developed, agricultural) by area within the corridor. For land cover data, the National Land Cover Database (NLCD) for 2006, 2001 and 1992 is accessible at http://www.mrlc.gov/finddata.php Exit EPA Disclaimer; numerous statewide land cover mapping datasets are also available from state-specific sources. This metric can also be measured with a narrow corridor width or as a linear feature to identify specifically the land-water interface proportions that are in human-altered cover types.

 

corridor % urban (PDF) (6 pp, 63.7K, About PDF)

Why relevant to recovery: As the intensity of urbanization increases, biotic integrity tends to decrease. Developed land cover in riparian zones is associated with aquatic biota more tolerant of pollutants. Increasing substrate embeddedness and bank erosion have also been observed to increase in streams in developing areas. Significantly lower water quality is often found downstream of highly developed corridors where not attributable to treatment plant discharges. Human shoreline development may lead to loss of littoral habitats. Threshold responses to percentages of development found in corridors were not borne out also at the watershed scale, indicating potentially greater significance of corridor vs watershed effects from urbanization.

Data sources and measurement: Extracted from land cover mapping within a set corridor width, and summarized as % developed (e.g., residential, commercial, industrial, urban center, etc) by area within the corridor. For land cover data, the National Land Cover Database (NLCD) for 2006, 2001 and 1992 is accessible at http://www.mrlc.gov/finddata.php Exit EPA Disclaimer; numerous statewide land cover mapping datasets are also available from state-specific sources.

 

corridor % agriculture (PDF) (5 pp, 51.9K, About PDF)

Why relevant to recovery: Croplands and pastures have been linked to a wide variety of water quality and biotic impacts on waters. Agriculture within stream corridors is sometimes more highly linked with several impairment types than agriculture generally distributed in the watershed, but often watershed percentage also appears to be a strong influence. Common effects seen at moderate to high agricultural proportions of land cover include less diverse and more intolerant macrobenthic communities, increased nutrient loading resulting in turbid water, overall homogenization of the fish fauna, accelerated erosion and bank destabilization, suspended sediment particles carrying pesticides, pathogens, and heavy metals, habitat degradation and reduced biodiversity, and increases in specific conductivity, DIN, DRP, and TP concentrations. Although agriculture is commonly linked to degraded aquatic conditions that may be difficult to reverse and quite persistent over time, it is important to note that some degree of recovery is rarely considered impossible; for example, livestock access to channels may be more influential than corridor agricultural use and is commonly feasible to reduce. However, some studies claim that agriculture on floodplains can constrain the benefits of restoring natural hydrologic processes.

Data sources and measurement: Calculated as % by area within a set corridor width (e.g., 30 M or 90 M on each side); often cropland and pasture are compiled as separate metrics. Land cover sources include the National Land Cover Data from 1992 (See: http://www.epa.gov/mrlc/nlcd.html), 2001 (See: http://www.epa.gov/mrlc/nlcd-2001.html), and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer) as well as various state sources. The USGS lists cropland by county since 1850 (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). If the user chooses to use this indicator for a specific crop relevant to the study area, USDA has developed a national GIS crop dataset that can be downloaded from Geospatial Data Gateway (See: http://datagateway.nrcs.usda.gov/GDGHome.aspx Exit EPA Disclaimer). In addition, where applicable, BLM data set on range allotments and pastures can be used (See: http://www.geocommunicator.gov/GeoComm/ Exit EPA Disclaimer).

 

linear % of channel through agriculture

Why relevant to recovery: Croplands and pastures have been linked to a wide variety of water quality and biotic impacts on waters (see watershed % agriculture, corridor % agriculture). The actual land/water interface along streams that pass through agricultural areas can vary substantially in its relevance to agriculture-related impairment; corridors or watersheds with high proportions of agriculture may still have well-vegetated buffers, or may be farmed or grazed all the way to the channel. Unbuffered shorelines are more erosion-prone, deliver more sediment and pollutants such as pesticides and fertilizers in runoff, can elevate water temperatures, and other impacts that hinder and complicate recovery.

Data sources and measurement: Overlaid stream hydrography and land cover enables quantifying this metric on a segment or watershed basis. Calculation can be performed as a linear measurement if the watershed contains only linear streams, but can also be approximated by calculating % area within a very narrow (e.g., 1 meter) buffer. An equivalent approach allows for lake shores to be characterized. Resolution of the land cover source should be considered, as thin buffers may not be detected or mapped. A slightly different way to quantify the agriculture/flowing water interface involves looking also at flow accumulation paths generated from digital elevation data. These 'low spots' may not have channels but where coinciding with agricultural lands they have some likelihood of transporting agricultural runoff to surface waters nearby.

 

corridor road crossings (PDF) (2 pp, 43.3K, About PDF)

Why relevant to recovery: Road crossings are linked with degraded condition for several reasons, but because most crossings are likely permanent, their relevance to recovery potential is also linked to whether the degraded conditions can be managed or mitigated for. Road crossings are linked with channel destabilization, tree collapse, hanging tributary junctions as a result of variable incision rates, and erosion around artificial structures including bridges. Local scouring alters sedimentation and deposition processes, and more sediment and chemicals enter streams where a road crosses. Wetland road crossings often block drainage passages and groundwater flows, effectively raising the upslope water table and killing vegetation by root inundation, while lowering the downslope water table. Small road crossings for which the culverts do not allow upstream fish passage and constrict the available useful habitat for salmonids already vulnerable to other impacts.

Data sources and measurement: Measured as number of crossings per stream mile. Land cover or transportation GIS data are widely available. National road and stream data is obtainable through the National Atlas (See: http://nationalatlas.gov/ Exit EPA Disclaimer). Landsat data is also often used for road and stream data and can be accessed through the USGS Earth Explorer (See: http://edcsns17.cr.usgs.gov/EarthExplorer/ Exit EPA Disclaimer). ESRI offers a free roads dataset (http://www.arcgis.com/home/item.html?id=3b93337983e9436f8db950e38a8629af Exit EPA Disclaimer). Data on unimproved road crossings in remote parts of federal lands may need to be obtained through the land management agency.

 

corridor road density (PDF) (3 pp, 48.5K, About PDF)

Why relevant to recovery: Riparian corridor roads can affect sedimentation and deposition processes, increase siltation to the detriment of aquatic biota, compact floodplain substrates and reduce recharge that would help maintain base flow, and increase pollutants such as road salts that raise conductivity and harm stream invertebrates and fish. Because most stream corridor roads are likely permanent, their relevance to recovery potential is also linked to whether the degraded conditions can be managed or mitigated for.

Data sources and measurement: Measured as mean road length per stream corridor area. Transportation GIS datasets are widely available and can be used in overlay with an impaired waters dataset with a corridor of set width (e.g., 30M, 90M per side) delineated. National road and stream data is obtainable through the National Atlas (See: http://nationalatlas.gov/ Exit EPA Disclaimer). Transportation GIS datasets (e.g., ESRI transportation http://www.arcgis.com/home/item.html?id=3b93337983e9436f8db950e38a8629af Exit EPA Disclaimer) are widely available and can be used in overlay with an impaired waters dataset with a corridor of set width (e.g., 30M, 90M per side) delineated. 90M is preferable for this metric in order to ensure that roads that generally parallel the channel are detected and counted.

 

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Hydrologic alteration

aquatic barriers (PDF) (14 pp, 215K, About PDF)

Why relevant to recovery: This metric is often relevant to evaluating restoration prospects for bio-impairments. Barriers that fragment aquatic populations of marginal size may reduce the viability of each fragment. Barriers often also can prevent or delay recolonization of areas with diminished or absent populations. Barriers may be natural (waterfalls, major habitat changes) as well as artificial (perched culverts, buried streams, dams), and may be physico-chemical (temperature, toxicity) as well as structural. Unless species reintroduction is feasible to circumvent a problem that cannot be removed or modified, barriers are sometimes insurmountable obstacles to aquatic community recovery.

Data sources and measurement: Barrier influence is most easily measured as a count per watershed, but more meaningfully scored on the basis of relative isolation of specific segments from waters of similar (+ or - 1 Strahler order) size. Depending on motility of the species of interest, the height considered impassable and the barrier's upstream or downstream location may be considered. Where information on the dam types is limited, the metric can be measured in terms of barriers presence/absence. Aquatic barriers for fish passage are documented through the US Fish and Wildlife Fish Passage Decision Support System (See: http://fpdss.fws.gov/home Exit EPA Disclaimer). Major dams have been mapped through the US Army Corps of Engineers' National Inventory of Dams (See: http://www.usace.army.mil/Library/Maps/Pages/NationalInventoryofDams.aspx Exit EPA Disclaimer) but the large numbers of smaller dams on small to medium-scale streams and rivers are not uniformly documented. In addition, National Hydrography Dataset (NHD) contains data on dams and divergence structures (http://nhd.usgs.gov/ Exit EPA Disclaimer). Some types of barrier information may be available from monitoring.

 

channelization (PDF) (4 pp, 126K, About PDF)

Why relevant to recovery: Channelization is a major modification of natural form that results in habitat simplification and reduction in frequency of specific, life-supporting habitat types (e.g. pools, spawning gravels). The process also destabilizes erosion/deposition dynamics, shortens residence time during which excess nutrients may be processed, and increases risks of downstream erosion and channel destabilization with accompanying loss of use or property. Negative impacts on biological communities are well documented not only within channelized reaches but at substantial distances downstream. The significance of this metric in reducing recovery potential is based on multiple effects: degraded habitat, altered primary physical processes, destabilized instream conditions, persistence of negative effects for decades, and high expense of reengineering channel sinuosity.

Data sources and measurement: The simplest manner of measuring channelization is as the percent of total impaired segment length that is artificially straightened, as observable on imagery or mapped media. Straight channels are easily detected, but highly reduced sinuosity (which often has similar effects) is less easily identified unless factors such as valley slope and expected vs observed sinuosity are measured. Additional measurements may choose to consider the channelized length per watershed area, whether lined or armored banks or bed are present, and percent of channelized length weighted by Strahler stream order. A visual inspection of these data is the best way to identify presence/absence of channelization, after which measurement of length channelized and impaired 303(d) reach length can be carried out via GIS to obtain the % channelized and total channelized length. Except on very short reaches or the smallest channel orders, much channelization is visible on high resolution surface hydrography data such as data available through the National Hydrography Dataset (See: http://nhd.usgs.gov/ Exit EPA Disclaimerdata.html) or local resources. Manual visual interpretation from GIS hydrographic data, although somewhat laborious, is effective for identifying and measuring the length/percent of channelized reaches in each impaired waterbody segment. Channelization presence/absence is sometimes reported as a cause for 303(d) listing and available as attribute data from EPA's ATTAINS data system (See: http://www.epa.gov/waters/ir/).

 

hydrologic alteration (PDF) (26 pp, 304K, About PDF)

Why relevant to recovery: Several different forms of hydrologic alteration (i.e., mainly timing, magnitude and influences of flow on other natural processes) have resulted in dramatic shifts in river flow regimes, sediment transport and deposition patterns, temperature, nutrients, fish assemblages, floodplain isolation, altered high and low flow, and floodplain land use. Numerous additional effects are noted in the literature excerpts below. Most U.S. river systems are hydrologically altered by dams, but water diversions or withdrawals, channelization and human-made disruptions of overland flow also produce hydrologic alteration. Significant departure of an impaired waterbody from its range of natural flow variability is the most common mechanism among these that negatively influences recovery potential. However, dam removal, adjusting flow regulation at dams or the changing the seasonality or timing of withdrawals is often possible and can bring about recovery in many flow-altered waters.

Data sources and measurement: A scoring process of waterbody segments downstream of dams or withdrawals can consider dam sizes, active status, role on flow alteration, and feasibility of flow management. Where information on the dam types is not available, the metric can be measured in terms of dam presence/absence. Aquatic barriers for fish passage (including culverts) are documented through the US Fish and Wildlife Fish Passage Decision Support System (See: http://fpdss.fws.gov/home Exit EPA Disclaimer). Major dams have been mapped through the US Army Corps of Engineers' National Inventory of Dams (See: http://www.usace.army.mil/Library/Maps/Pages/NationalInventoryofDams.aspx Exit EPA Disclaimer) but the large numbers of smaller dams on small to medium-scale streams and rivers are not uniformly documented. National Hydrography Dataset (NHD) contains data on dams and divergence structures (http://nhd.usgs.gov/ Exit EPA Disclaimer). Data on water withdrawal locations may vary highly among states. An example of state withdrawal information can be found through the Michigan Department of Natural Resources and Environment (See: http://michigan.gov/deq/0,1607,7-135-3313_3677_3704-72931--,00.html).

 

relative net water demand

Why relevant to recovery: Stressors affecting the natural flow regime can have numerous secondary impacts. Ecological responses to flow alterations include loss of sensitive species, reduced diversity, altered assemblages and dominant taxa, reduced abundance, and increases in non-native species. Human water use can affect the magnitude, frequency, and duration of streamflows. For this metric, ratios of impacted streamflow to natural streamflow are used as indices to describe the magnitude of hydrologic alteration. Specifically, in this USGS-developed metric annual withdrawal and discharge are averaged and disaggregated to a one-year time series of daily flow. Net daily water use is subtracted from natural streamflow to get impacted streamflow for the period of record.

Data sources and measurement: Flow information is usually limited, but gaging station records can sometimes be used to develop natural flow estimators and calculate this metric relative to natural flow.

 

water use intensity

Why relevant to recovery: Stressors affecting the natural flow regime can have numerous secondary impacts. Ecological responses to flow alterations include loss of sensitive species, reduced diversity, altered assemblages and dominant taxa, reduced abundance, and increases in non-native species. Human water use can affect the magnitude, frequency, and duration of streamflows. For this metric, ratios of impacted streamflow to natural streamflow are used as indices to describe the magnitude of hydrologic alteration. Specifically, this USGS-developed metric is a ratio defined as the sum of the absolute value of withdrawals and return flows relative to the long-term average unaltered streamflow from a watershed. The WUI indicator is used to identify "churned" basins, where human flows (withdrawals and return flows) are similar to each other but each individually is a large proportion of natural streamflow.

Data sources and measurement: Flow information is usually limited, but gaging station records can sometimes be used to develop natural flow estimators and calculate this metric relative to natural flow.

 

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Biotic or climatic risks

elevation (PDF) (3 pp, 54.6K, About PDF)

Why relevant to recovery: Specific to waters with bio-impairments involving coldwater fish populations. For a given state or sub-state region, the range of elevations among different bio-impaired waters may provide part of the basis for comparing the likelihood of reestablishing coldwater temperature regimes, all other factors aside. Lower elevations correlate with greater vulnerability of coldwater aquatic communities and difficulty in their restoration, especially in consideration of expected climate change. Secondarily, the warmer water temperature regimes can increase chemical pollutant availability or toxicity and oxygen depletion.

Data sources and measurement: Measured as mean elevation of the watershed or the specific stream/river segment. Field data or models may be usable to estimate elevation thresholds below which recovery of a coldwater system or species is unlikely. The National Elevation Dataset (NED) (http://nhd.usgs.gov/ Exit EPA Disclaimerindex.html) is adequate for arraying a set of waters into quantiles based on mean elevation. High resolution elevation data should be used for any assessment units at HUC12 level of smaller. The Elevation Derivatives for National Applications (EDNA) has been derived from the NED and is hydrologically conditioned to improve hydrologic flow representation (See: http://edna.usgs.gov/ Exit EPA Disclaimer). NHD plus contains information on maximum and minimum elevation for each flowline (http://www.horizon-systems.com/nhdplus/ Exit EPA Disclaimer).

 

invasive species risk (PDF) (5 pp, 77K, About PDF)

Why relevant to recovery: Non-indigenous species (NIS) invasions are widely known to disrupt aquatic system function and inhibit recovery of altered systems. The rapid colonization typical of NIS may act to subvert expected succession pathways and thereby disrupt restoration planning. Altered structure due to aquatic or riparian NIS can reduce shade, inhibit native riparian vegetation cover, and increase sedimentation. Aquatic invaders may compete directly or prey upon key native species, reduce numbers or species diversity, and markedly alter food webs and ecological structure. Presence of NIS may actually be the impairment cause for listing, and recovery in such cases depends on eradication or control. Particularly relevant to recovery potential screening is the fact that some NIS, once established, cannot currently be controlled or eradicated by any known methods.

Data sources and measurement: In recovery potential screening, this metric may consider existing invasions or the risk of future invasions, or both. Many options for scoring can be developed, based on the state. An example quantile scoring process is:

  • 0 - no established NIS of concern, no immediate risk;
  • 1 - no established NIS of concern, risk due to proximity or other vulnerability;
  • 2 - established NIS of concern exists, control or eradication feasible;
  • 3 - established NIS of concern exists, control or eradication infeasible.
This scoring approach can be customized for NIS species-specific rankings, direct influence on prospects of reattaining the unmet water quality standard, or to consider multiple NIS problems per waterbody.

Data availability may be through waterbody-specific monitoring information on occurrence, such as the USGS Non-Indigenous Aquatic Species Information Resource (See: http://nas.er.usgs.gov/default.aspx) or through Non-Indigenous Species Database Network range maps by species (http://www.nisbase.org/nisbase/index.jsp Exit EPA Disclaimer) which include a variety of participating databases. The USDA National Invasive Species Information Center also contains links to several databases (See: http://www.invasivespeciesinfo.gov/resources/databases.shtml Exit EPA Disclaimer). Availability of either is highly variable and difficult to update under rapid changes.

 

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Severity of pollutant loading

number of 303d listed causes (PDF) (1 pp, 11.9K, About PDF)

Why relevant to recovery: The number of stressors affecting and impaired water body is generally a direct indication of the relative complexity, expense and difficulty of its restoration, according to many practitioners. More pollutants causing impairments frequently implies more numbers and diverse types of responsible sources. The number of listing causes also may be associated with greater magnitude of impairment due to cumulative effects.

Data sources and measurement: Number of pollutant causes per listed water body segment, or number of listed cause/waterbody segment combinations per watershed, which are both identifiable from EPA data systems available online. If the reporting unit contains more than one listed waterbody segment, the total number of pollutant causes per length of listed waterbodies can be measured. The Assessment TMDL Tracking and Implementation System (ATTAINS) (See: http://www.epa.gov/waters/ir/) contains information on 303d-listed waters by state and by semi-annual reporting cycle. States may also have more detailed information.

 

number of permits

Why relevant to recovery: Although point source discharge permits are a tool for pollution control, the abundance of permits in a given watershed can be associated with a number of secondary effects on restorability. Mainly, the occurrence of many permits correlates with high levels of commercial and industrial activity, all stressors from which may not necessarily be controlled by the permits. Legacy pollutants from these land uses may exist. Further, unless all permits were developed from a watershed basis, their collective loads may exceed what can be assimilated.

Data sources and measurement: Permit outfall and facility locations are available in GIS datasets on a national basis and in most states. EPA's national geospatial dataset on permits contains permit latitude-longitude point information for outfalls or secondarily for permitted facility locations.

 

CSO or MS4 areas

Why relevant to recovery: Public sewer systems are designed to handle stormwater runoff and its pollutants, up to a point. Exceeding the capacity of a system can result in an episodic increase in pollutant loadings and complicate efforts at restoration. Existence of CSO or MS4 areas in a watershed as well as the capacity of the systems can be a consideration when evaluating stressors that affect recovery.

Data sources and measurement: Generally these areas are available in mapped form at state or municipal level.

 

age of sewer infrastructure

Why relevant to recovery: Older sewerage infrastructure can be a more important stressor than new construction and thus affect recovery prospects in some watersheds. Pipe failures and leaks with age are more common in older systems.

Data sources and measurement: Generally the ages of infrastructure piping are available from municipalities, sometimes in mapped form.

 

severity of loading (PDF) (2 pp, 15K, About PDF)

Why relevant to recovery: For impaired waters where needed load reductions have been calculated, the magnitude of necessary reductions compared with current loadings has been shown to relate to likelihood of successful restoration, although this metric is not necessarily a determinant of irreversible degradation. Case studies of restoration successes showed multiple cases where if needed load reductions were less than 50% of current levels, more restoration successes were achieved. The 50% figure is likely not a consistent threshold value and data of this sort are limited, thus the metric is best used to array a set of waters into quantiles based on expert judgment about % loading reduction.

Data sources and measurement: Data sources and measurement: The measure compares the current loading estimates with the TMDL target loading calculation, in terms of the percent reduction needed. The Assessment TMDL Tracking and Implementation System (ATTAINS) (See: http://www.epa.gov/waters/ir/) contains information on 303(d)-listed waters by state and by semi-annual reporting cycle. Loading estimates generally need to come from completed TMDLs or watershed models. Most completed TMDLs are available online via state or EPA websites (see also http://www.epa.gov/waters/tmdl/expert_query.html).

 

stressor persistence (PDF) (2 pp, 97K, About PDF)

Why relevant to recovery: Stressors causing impairment can vary considerably in their likelihood to persist over long periods, or to naturally dissipate or respond rapidly to controls. This can be due to the nature of the stressor itself (e.g., radionuclides), its source (e.g., unremediated acid mine drainage), or its setting (e.g., excess fine sediment persistence in lower gradient streams). Comparison of recovery potential across many watersheds can consider differences in persistence across different stressor types and settings.

Data sources and measurement: Methods for measurement would be project-specific, and differ with the stressors included. One option for developing persistence metrics involving different stressors and settings is to use high/medium/low categories specific to each stressor.

SPARROW nitrogen loading estimate

Why relevant to recovery: SPARROW is one of the most widely used geospatial models for estimating nutrient pollution on a watershed basis, and has been used to estimate nitrogen and phosphorus loads and yields over large areas at the HUC8 and HUC12 scales. These models identify urban and agricultural sources as major contributors of nutrients to streams and reveal local and regional differences in nutrient contributions from contrasting types of agricultural (farm fertilizers vs. animal manure) and urban (wastewater vs diffuse runoff from developed land) sources.

Data sources and measurement: The EPA's NPDAT website (see http://www.epa.gov/nutrientpollution/npdat/) provides an introductory website, geospatial viewer, and data downloads as well as associated water quality information.  An online, interactive USGS decision support system Exit EPA Disclaimer also provides easy access to regional models describing how rivers receive and transport nutrients from natural and human sources to sensitive waters, such as the Gulf of Mexico.

 

SPARROW phosphorus loading estimate

Why relevant to recovery: SPARROW is one of the most widely used geospatial models for estimating nutrient pollution on a watershed basis, and has been used to estimate nitrogen and phosphorus loads and yields over large areas at the HUC8 and HUC12 scales. These models identify urban and agricultural sources as major contributors of nutrients to streams and reveal local and regional differences in nutrient contributions from contrasting types of agricultural (farm fertilizers vs. animal manure) and urban (wastewater vs diffuse runoff from developed land) sources.

Data sources and measurement: The EPA's NPDAT website (see http://www.epa.gov/nutrientpollution/npdat/) provides an introductory website, geospatial viewer, and data downloads as well as associated water quality information. An online, interactive USGS decision support system Exit EPA Disclaimer also provides easy access to regional models describing how rivers receive and transport nutrients from natural and human sources to sensitive waters, such as the Gulf of Mexico.

 

watershed stream miles impaired

Why relevant to recovery: Although state monitoring programs are generally unable to assess all of their waters in each integrated reporting cycle, the relative quantity of reported impairments provides an important insight into what is currently known. Larger quantities or proportions of impaired stream miles imply a likely more complex and extensive watershed restoration task, and also may be associated with additional unmonitored impairments within adjacent or connected streams and other water bodies.

Data sources and measurement: This metric can be used as a quantity (total impaired miles per watershed) or as a proportion (impaired miles per total stream miles in the watershed, impaired miles per total watershed miles assessed). A national geospatial impaired waters dataset is available through EPA's Assessment TMDL Tracking and Implementation System (ATTAINS) (See: http://www.epa.gov/waters/ir/). This source contains information on 303(d)-listed waters by state and by semi-annual reporting cycle.

 

watershed water body acres impaired

Why relevant to recovery: Although state monitoring programs are generally unable to assess all of their waters in each integrated reporting cycle, the relative quantity of reported impairments provides an important insight into what is currently known in each watershed. Larger quantities or proportions of impaired water body acres imply a likely more complex and extensive watershed restoration task, and also may be associated with additional unmonitored impairments within adjacent or connected streams and other water bodies.

Data sources and measurement: This metric can be used as a quantity (total impaired acres per watershed) or as a proportion (impaired acres per total water body acres in the watershed, impaired acres per total watershed acres assessed). A national geospatial impaired waters dataset is available through EPA's Assessment TMDL Tracking and Implementation System (ATTAINS) (See: http://www.epa.gov/waters/ir/). This source contains information on 303(d)-listed waters by state and by semi-annual reporting cycle.

 

modeled watershed aerial N deposition

Why relevant to recovery: Excessive N loadings to waters cause a number of adverse effects, whether from land-based sources or aerial deposition. Aerial deposition is worth separate consideration as a factor inhibiting recovery potential as the likelihood of successful control of the aerial sources is independent of the likelihood of controlling the within-watershed point or nonpoint sources of N. Where aerial sources continue to be the primary sources of N, watershed-based restoration efforts alone might be expected to have low recovery potential.

Data sources and measurement: Data sources and measurement: Modeled N deposition across large regions may be available for selected areas at a resolution that enables aggregation into N deposition values at a given watershed scale, e.g., HUC12s. Likely that original model outputs are not on a watershed basis, but areal weighting methods allow for translating values to a watershed basis.

 

modeled watershed aerial Hg deposition

Why relevant to recovery: Over 8700 waterbodies in 43 States plus the District of Columbia and Puerto Rico are listed as impaired under section 303(d) of the Clean Water Act due to excessive amounts of mercury in fish tissue or in the water column. Atmospheric deposition is believed to be the dominant avenue by which mercury loads are delivered to most watersheds, although some waters have significant inputs from sources such as historic mine tailings and/or enriched minerals. A discussion of the adverse effects of mercury on human health, especially for unborn children, as well as ecological impacts can be found at http://www.epa.gov/mercury/about.htm.

Data sources and measurement: In order to support development and implementation of TMDLs for mercury in areas impacted by atmospheric deposition, EPA's Office of Water in cooperation with State and Regional partners has completed deposition modeling. The Regional Modeling System for Aerosols and Deposition (REMSAD) was the primary model relied upon in this analysis. The Community Multi-scale Air Quality Model (CMAQ) was also used to provide a "second opinion" of key REMSAD findings. In addition, three different global models were used in order to provide a range of likely impacts from foreign sources. The domain of this modeling was the lower continental US and the spatial resolution was a network of 12km by 12km grid cells throughout the domain (see http://water.epa.gov/lawsregs/lawsguidance/cwa/tmdl/techsupp.cfm).

 

other stressor-specific severity factors

Why relevant to recovery: The broad variety of impairment causes that can affect degraded waters may vary substantially from one another in relative difficulty of restoration. A given area may, for example, find their urban runoff impairments far more difficult to remediate than their rural pathogen impairments. This metric relates to differentiating between specific stressors and their generalized differences in restorability as a recovery potential indicator concept. This concept can also be applied to develop single-stressor-based indicators that recognize recovery potential differences related to loading magnitude, frequency, duration, or association with other factors that influence restorability.

Data sources and measurement: Project-specific and stressor-specific measurement methods need to be developed to use this indicator.

 

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Legacy of past, trajectory of future land use

land use change trajectory (PDF) (4 pp, 72.6K, About PDF)

Why relevant to recovery: Human use effects in watersheds that influence recovery can be observed not just by current conditions, but also by recent changes in those conditions. Recent land cover trajectory studies may suggest the likely direction of continued pressures, such as continuing urbanization, deforestation, or agricultural expansion. Also, recent changes may not have fully produced impacts that can occur over several years. Some studies have suggested that decades-old land use history is sometimes more correlated with aquatic impairment than recent land use pattern.

Data sources and measurement: Land cover totals (%) for given watersheds can be contrasted for different past time periods. Buildout scenario projects may be sources of estimating future change trajectory, as are data sources that identify high-growth urban areas. Specific changes are more easily tracked than attempting to summarize all watershed change types in one metric - for example, one can separately estimate recent loss in % forest, gain in % urban, and gain in % agriculture in each watershed of interest. National Land Cover Data from 1992 (See: http://landcover.usgs.gov/natllandcover.php Exit EPA Disclaimer), 2001 (See: http://www.mrlc.gov/index.php Exit EPA Disclaimer), and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer) can be contrasted at the watershed level. MRLC provides calculated data on developed imperviousness change, as well as the change for all of the NLCD land use classes, between 2001 and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer). The USGS is a source for several land use change datasets, including the Land Cover Trends Project (See: http://landcovertrends.usgs.gov/download/overview.html Exit EPA Disclaimer) and the Temporal Urban Mapping project (See: http://landcover.usgs.gov/urban/umap/ Exit EPA Disclaimer). State or local data on land cover change are not common and may present technical challenges to data comparability over time. The Historical Topographic Map Collection includes published U.S. maps of all scales and editions, and are offered as a georeferenced digital download or as a scanned print from the USGS Store (see http://nationalmap.gov/historical/ Exit EPA Disclaimer).

 

legacy land uses (PDF) (6 pp, 80.9K, About PDF)

Why relevant to recovery: A variety of impacts on waters are associated with agricultural uses in general, including increased loadings of nutrients, fine sediment, pesticides, herbicides, flow alteration, elevated water temperature, and others. A past history of agriculture in the watershed and/or riparian corridor can continue to account for adverse effects even after land use change (vegetational succession, transition to residential or other uses) has replaced the agriculture. Built-up nutrients and pesticides/herbicides in groundwater can continue to be discharged through influent groundwater connections for decades. Excess fine sediments and channel widening (which reduces channel habitat quality) caused during active agriculture can also persist for years to decades, as can channel destabilization and related erosion. Some studies suggest that a past history of agricultural use is more strongly correlated with impairment than current, other land use patterns.

Data sources and measurement: Although geospatial data on past agriculture is date-limited, one national digital source (LUDA/GIRAS) characterized agricultural usage in the 1970s at coarse resolution. Locally older data may be available in isolated areas, or where historical aerial analyses back to the 1930s may have been conducted using airphotos. Measurable with suitable data as percent by area within watershed or corridor. Historical land cover data is available through the USGS Land Cover Institute (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). NLCD land cover data is available as far back as 1992 (http://landcover.usgs.gov/natllandcover.php Exit EPA Disclaimer). MRLC provides calculated data on the change for all of the NLCD land use classes between 2001 and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer). The Historical Topographic Map Collection includes published U.S. maps of all scales and editions, and are offered as a georeferenced digital download or as a scanned print from the USGS Store (see http://nationalmap.gov/historical/ Exit EPA Disclaimer).

 

watershed % legacy agriculture (PDF) (5 pp, 69.5K, About PDF)

Why relevant to recovery: A variety of impacts on waters are associated with agricultural uses in general, including increased loadings of nutrients, fine sediment, pesticides, herbicides, flow alteration, elevated water temperature, and others. A past history of agriculture in the watershed and/or riparian corridor can continue to account for adverse effects even after land use change (vegetational succession, transition to residential or other uses) has replaced the agriculture. Built-up nutrients and pesticides/herbicides in groundwater can continue to be discharged through influent groundwater connections for decades. Excess fine sediments and channel widening (which reduces channel habitat quality) caused during active agriculture can also persist for years to decades, as can channel destabilization and related erosion. Some studies suggest that a past history of agricultural use is more strongly correlated with impairment than current, other land use patterns.

Data sources and measurement: Although geospatial data on past agriculture is date-limited, one national digital source (LUDA/GIRAS) characterized agricultural usage in the 1970s at coarse resolution. Locally older data may be available in isolated areas, or where historical aerial analyses back to the 1930s may have been conducted using airphotos. Measurable with suitable data as percent by area within watershed or corridor. Historical land cover data is available through the USGS Land Cover Institute (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). NLCD land cover data is available as far back as 1992 (http://landcover.usgs.gov/natllandcover.php Exit EPA Disclaimer). MRLC provides calculated data on the change for all of the NLCD land use classes between 2001 and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer).

 

watershed % legacy urban (PDF) (2 pp, 54K, About PDF)

Why relevant to recovery: The age of an urbanized area or specifics of its history may have implications for its legacy pollutants in groundwater that can affect recovery. Built-up urban and industrial pollutants in groundwater can continue to be discharged through influent groundwater connections for decades.

Data sources and measurement: Measured as % urban land cover categories from a historic source. Although geospatial data on past urban land is date-limited, one national digital source (LUDA/GIRAS) characterized urban usage in the 1970s at coarse resolution (10 acre mapping unit). Locally older data may be available in isolated areas, or where historical aerial analyses back to the 1930s may have been conducted using airphotos. Measurable with suitable data as percent by area within watershed or corridor. Historical land cover data is available through the USGS Land Cover Institute (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). NLCD land cover data is available as far back as 1992 (http://landcover.usgs.gov/natllandcover.php Exit EPA Disclaimer). MRLC provides calculated data on the change for all of the NLCD land use classes between 2001 and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer). The Historical Topographic Map Collection includes published U.S. maps of all scales and editions, and are offered as a georeferenced digital download or as a scanned print from the USGS Store (see http://nationalmap.gov/historical/ Exit EPA Disclaimer).

 

corridor % legacy agriculture (PDF) (5 pp, 71.9K, About PDF)

Why relevant to recovery: A variety of impacts on waters are associated with agricultural uses in general, including increased loadings of nutrients, fine sediment, pesticides, herbicides, flow alteration, elevated water temperature, and others. A past history of agriculture in the watershed and/or riparian corridor can continue to account for adverse effects even after land use change (vegetational succession, transition to residential or other uses) has replaced the agriculture. Built-up nutrients and pesticides/herbicides in groundwater can continue to be discharged through influent groundwater connections for decades. Excess fine sediments and channel widening (which reduces channel habitat quality) caused during active agriculture can also persist for years to decades, as can channel destabilization and related erosion. Some studies suggest that a past history of agricultural use is more strongly correlated with impairment than current, other land use patterns.

Data sources and measurement: Although geospatial data on past agriculture is date-limited, one national digital source (LUDA/GIRAS) characterized agricultural usage in the 1970s at coarse resolution. Locally older data may be available in isolated areas, or where historical aerial analyses back to the 1930s may have been conducted using airphotos. Measurable with suitable data as percent by area within watershed or corridor. Historical land cover data is available through the USGS Land Cover Institute (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). NLCD land cover data is available as far back as 1992 (http://landcover.usgs.gov/natllandcover.php Exit EPA Disclaimer). MRLC provides calculated data on the change for all of the NLCD land use classes between 2001 and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer).

 

corridor % legacy urban

Why relevant to recovery: The age of an urbanized area or specifics of its history may have implications for its legacy pollutants in groundwater that can affect recovery. Built-up urban and industrial pollutants in groundwater can continue to be discharged through influent groundwater connections for decades.

Data sources and measurement: Measured as % urban land cover categories from a historic source. Although geospatial data on past urban land is date-limited, one national digital source (LUDA/GIRAS) characterized urban usage in the 1970s at coarse resolution (10 acre mapping unit). Locally older data may be available in isolated areas, or where historical aerial analyses back to the 1930s may have been conducted using airphotos. Measurable with suitable data as percent by area within watershed or corridor. Historical land cover data is available through the USGS Land Cover Institute (See: http://landcover.usgs.gov/cropland/index.php Exit EPA Disclaimer). NLCD land cover data is available as far back as 1992 (http://landcover.usgs.gov/natllandcover.php Exit EPA Disclaimer). MRLC provides calculated data on the change for all of the NLCD land use classes between 2001 and 2006 (http://www.mrlc.gov/nlcd06_data.php Exit EPA Disclaimer). The Historical Topographic Map Collection includes published U.S. maps of all scales and editions, and are offered as a georeferenced digital download or as a scanned print from the USGS Store (see http://nationalmap.gov/historical/ Exit EPA Disclaimer).


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