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GIS in Watershed AnalysisGIS in Watershed AnalysisGIS in Watershed AnalysisGIS in Watershed Analysis
Why watershed Analysis with GIS?Why watershed Analysis with GIS?
• Concepts
• Important datasets
• Analysis Tools
Regional stressorsRegional stressors
Impacts of Human ActivitiesImpacts of Human Activities
Stream alterationsAgriculture
MiningTimber
Watershed based frameworksWatershed based frameworks• Integrative approach• Legislative roots in the 1972 Clean Water Act
– Goal to clean up and protect US water bodies from point and nonpoint sources
Designated uses – evaluated as part of the Clean Water Act
2012
Watershed cataloging unitsWatershed cataloging units
USGS Regions (2 digit)
Watershed cataloging unitsWatershed cataloging units
USGS Sub-regions (4 digit)
Watershed cataloging unitsWatershed cataloging units
USGS Sub-basins (8 digit)
http://datagateway.nrcs.usda.gov/
NRCS WBDNRCS WBD
• Watershed Boundary Dataset (WBD)
• HUC 8, 10, 12 and beyond
Issues Issues
• More local watersheds needed
• One to one relationship between land cover runoff and receiving stream segment
• Track runoff from land to stream
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Example of scale differencesExample of scale differences
DNR Stocked streams
Tier 2.5 - Reproducing trout streams
Impaired streams
Watershed boundaries
Previous methodPrevious method• Delineate watershed boundaries using the
topography to guide us
Manual methodManual method
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subwatershedssubwatersheds
Segment-level watershedsSegment-level watersheds
• Benefits:– Hydrologically
based– Not based on
drainage area cutoffs
– Not based on management areas
– Stream segment by segment
– Fully compatible with 1:100K and 1:24K NHD
– Networked, based on NHD
Existing issueExisting issue
• Nesting of watersheds• Pass through issues
Watershed modelingWatershed modeling
• Segment level watersheds can be used in watershed modeling
• Also compiled flow tables for each watershed
Watershed Schematic:Simplified segment-level watershedsand associated flow table
Outlet
Geospatial Technologies and Water ResourcesGeospatial Technologies and Water Resources
GTs in watershed management:
1. Elevation surface is key
2. Delineate watersheds
3. Track flow from a point
4. Find intermittent stream paths
5. Calculate drainage areas
• A valuable tool for water resources management
GIS use in the hydro cycleGIS use in the hydro cycle
Elevation surface or gridElevation surface or grid• The starting point for all hydrological modeling in GIS• USGS Digital elevation model 30m or 10m elevation
cells, or 3m for WV • Each cell or grid represents a value for the elevation
Summary pointsSummary points• Watersheds are the key unit of analysis for
examining water quality issues• Scale issues require us to delineate smaller
watersheds for local issues• GIS can aid in watershed management by
1. Using elevation grids2. Delineate watersheds3. Track flow from a point4. Find intermittent stream paths5. Calculate drainage areas
LimitationsLimitations
• Static snapshot of data
• Older Elevation grids
• Only modeling surface interactions
Questions / comments?Questions / comments?