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?