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Freshwater & Oceans

Tools for evaluating surface water supply

Wetland Prioritization Study Main Page

 

Single-objective tools

 

Multi-objective tools

 


 

The Nature Conservancy and Environmental Law Institute Duck-Pensaukee Watershed Approach Pilot Project (TNC-ELI DPWAP) Surface Water Supply Tool: A planning team assessed the ability of individual PRWs and preservation wetlands to perform surface water functions by evaluating each site for two types of criteria using a GIS-based approach:

  1. "Opportunity criteria" represented the possibility of provision of surface water benefits given the landscape context of each site evaluated.
  2. "Effectiveness criteria" represented the capability of wetlands to provide surface water benefits given the specific characteristics of each individual site.

Using GIS analysis, the team counted the number of opportunity and effectiveness criteria satisfied at each wetland site, with PRWs and existing wetlands analyzed separately. The team obtained the final score for each PRW or existing wetland by dividing the total count by the total number of opportunity or effectiveness criteria that could possibly have been satisfied. Assessing PRWs and existing wetlands separately, the team designated the top-scoring quarter of the sites to be "exceptional" priorities and the next quarter of sites to be "high" priorities. The lowest-scoring half of the sites were considered "low" priorities for PRWs (i.e., restoration) and were not considered priorities at all for existing wetlands (i.e., preservation). Factors and data sources used to assess surface water supply are listed below:

Factor used in analysis

Data source(s)

Wetland reestablishment opportunities (PRWs)

See above

Wetland preservation opportunities

See above

Opportunity criteria

Site is in a headwater setting

NWI+, Historic Wetland LLWW

Effectiveness criteria

Site is in a floodplain or fringe setting

NWI+, Historic Wetland LLWW, PRW

Site is a pond or lake with perennial throughflow or outflow

Historic Wetland LLWW, PRW

Acronym definitions

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Washington State Department of Ecology Watershed Characterization Tool (WSDOE WCT) Water Delivery Tool:1 The watershed characterization tool ranked user-defined hydrological units for groundwater recharge in terms of four possible "importance" and "impairment" rankings (low, medium, medium-high, and high). The model determines areas that have higher annual precipitation and contain higher coverage by rain-on-snow and snow-dominated zones to be more important for water delivery. Areas are more degraded for water delivery if they have poor timing of water delivery caused by large percent coverage by either non-forest vegetation or impervious surfaces.

Factor used in analysis

Data source(s)

Average annual precipitation weighted by area of extent

Precipitation isohyetal map

Timing of water delivery (rain-on-snow and snow-dominated zones)

Data layers from WNDR2

Percent non-forest vegetation

WDFW land use/land cover data3

Percent impervious surface

Acronym definitions

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Washington State Department of Ecology Watershed Characterization Tool (WSDOE WCT) Water Storage Tool:1,4 The watershed characterization tool ranked user-defined hydrological units for groundwater recharge in terms of four possible "importance" and "impairment" rankings (low, medium, medium-high, and high).The model considers the percent of depressional wetlands and percent unconfined and moderately confined floodplains to indicate areas that are important for surface water storage. For degradation, it considers the historic area of storage wetlands and unconfined and moderately unconfined floodplains impacted by urban and agricultural development.

Factor used in analysis

Data source(s)

Percent depressional wetlands

DNR topography; SSURGO hydric soils5

Percent unconfined and moderately confined floodplains

SSHIAP data for floodplain confinement6

Urban land use (i.e., moderate/high density residential, commercial and industrial)

WDFW land use/land cover data5

Rural/agricultural land use

WDFW land use/land cover data5

Miles of streams and rivers

Pacific Northwest Hydrography Network6

Area of unconfined and moderately confined floodplains

SSHIAP floodplain confinement data7

Acronym definitions

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Wetland Prioritization Study Main Page


1Stanley, S., S. Grigsby, D. B. Booth, D. Hartley, R. Horner, T. Hruby, J. Thomas, P. Bissonnette, R. Fuerstenberg, J. Lee, P. Olson, George Wilhere. 2011. Puget Sound Characterization. Volume 1: The Water Resources Assessments (Water Flow and Water Quality). Washington State Department of Ecology. Publication #11-06-016. Olympia, WA.
2 Washington State Department of Natural Resources. Available GIS Data – GIS Data Center. Accessible from: http://fortress.wa.gov/dnr/app1/dataweb/dmmatrix.html
3 Washington Department of Fish & Wildlife. Washington GAP Analysis Program: Land Cover Data. 2013. Accessible from: http://wdfw.wa.gov/conservation/gap/land_cover_data.html
4Feedback received on 5/18/2012 from Stephen Stanley, Wetland Specialist, Washington State Department of Ecology.
5 Natural Resources Conservation Service, USDA. SSURGO/STATSGO2 Structural Metadata and Documentation. Accessible from: http://soils.usda.gov/survey/geography/ssurgo/
6 Pacific Northwest Hydrography Framework (PNWHF) & Bureau of Land Management Oregon office. PNWHF National Hydrography Dataset (NHD). Accessible from: http://www.pnwhf.org/nat-hyd-dataset.aspx
7 Washington Department of Fish & Wildlife (WDFW). Conservation: SalmonScape. Salmon and Steelhead Habitat Inventory and Asessment Program (SSHIAP). 2013. Accessible from: http://wdfw.wa.gov/mapping/salmonscape/sshiap/