Tools for evaluating water quality | Environmental Law Institute

Single-objective tools

TNC-ELI DPWAP Water Quality Protection Tool
LACPRA CMP Nitrogen Uptake Spatial Statistical Approach
NHDES WRAM Sediment Trapping and Nutrient Potential Tool
WDNR Wetland Water Quality Assessment Tool

Multi-objective tools

The Nature Conservancy and Environmental Law Institute Duck-Pensaukee Watershed Approach Pilot Project (TNC-ELI DPWAP) Water Quality Protection Tool:¹ A planning team assessed the ability of individual Potentially Restorable Wetlands (PRWs) and preservation wetlands to perform water quality protection functions by evaluating each site for three types of criteria using a GIS-based approach:

"Opportunity criteria" represented the possibility of provision of water quality protection benefits given the landscape context of each site evaluated.
"Effectiveness criteria" represented the capability of wetlands to provide water quality protection benefits given the specific characteristics of each individual site.
"Social significance criteria" represented the extent to which water quality protection benefits for a site provided clear societal benefits.

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 highest-scoring quarter of all 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).

This tool scored each potential restoration (PRW) and preservation (existing wetland) site in terms of its ability to provide water quality services based on the opportunity, effectiveness, and social significance criteria listed below:

Factor used in analysis	Data source(s)
Wetland reestablishment opportunities (PRWs)	See above
Wetland preservation opportunities	See above
*Opportunity criteria*
Point source discharge upstream or directly into site	Wastewater Wisconsin Pollutant Discharge Elimination System (WPDES) Permit Program, NHDPlus Catchments (14-digit), NWI, PRW, 24k hydro
Site subject to nutrient loading from agricultural sources (row crops cover ›42% of catchment)	CCAP 2001, NHDPlus Catchments (14-digit)
Impervious surfaces cover › 10% of the site's catchment	2001 NLCD Impervious Surface Dataset from USGS via Data Basin, NHDPlus Catchments (14-digit), NWI, PRW
Site is not buffered by surrounding upland vegetation (‹50% of land within 200 feet is in natural cover)	CCAP 2001, Wetlands, PRW
*Effectiveness criteria*
Site has seasonally fluctuating water levels	NWI+, Historic Wetland LLWW, PRW
Site occurs in a topographic depression	NWI, PRW
Dominant vegetation is dense and persistent (forest, scrub-shrub, emergent marsh)	NWI, PRW
*Social significance criteria*
Wetland occurs in or above a catchment containing 303(d) waters.	24k Hydro WI DNR, 303d listed lines and areas from WI DNR
Surface connection to a lake, pond, river, or stream	NWI+, Historic Wetland LLWW, PRW

Acronym definitions

Louisiana Coastal Protection and Restoration Authority Coastal Master Plan (LACPRA CMP) Nitrogen Uptake Spatial Statistical Approach:² This method estimates nitrogen removal due to denitrification resulting from wetland protection or restoration projects in two steps. In the first, nitrogen removal was estimated for vegetation using the saline, brackish, intermediate, and freshwater habitat categories defined in the vegetation model. In the second step, benthic rates of denitrification were calculated by adjusting denitrification rates (identified in the first step) by salinity and temperature for each project site. Factors and data sources representing input variables for the model are listed below:

Factor used in analysis	Data source
Denitrification rates for vegetation and open water habitats	Estimates of denitrification rates for several wetland vegetation habitats throughout coastal Louisiana (Rivera-Monroy, 2010)
Salinity	Eco-hydrology model
Temperature	Eco-hydrology model

The New Hampshire Department of Environmental Services (NHDES) Wetland Restoration Assessment Model (WRAM) Sediment Trapping and Nutrient Potential Tool:³ The NHDES WRAM Sediment Trapping and Nutrient Attenuation Tool scores each National Wetland Inventory (NWI) wetland in terms of its ability to improve water quality based on the opportunity to capture pollutants (e.g., average slope of contributing watershed), potential to capture sediment (e.g., riparian buffer width of the site), potential for nutrient attenuation (e.g., dominant wetland class) and sediment loading potential (e.g., soil erodibility of upslope drainage). Factors and data used by WRAM to calculate water quality improvement for a wetland site are listed below:

Factor used in analysis		Data source(s)
Opportunity to capture pollutants	Average slope of contributing watershed	N/A
Opportunity to capture pollutants	Potential sources for sediments and nutrients	N/A
Potential for capture of sediment	Floodwater storage potential	N/A
	Riparian buffer width of the site	N/A
	Dominant wetland class	N/A
	Area of impounded water	N/A
Potential for nutrient attenuation	Potential for sediment trapping	N/A
	Dominant wetland class	N/A
	Level 1 Assessment Unit (AU) score	NHDES
Sediment loading potential	Land use of upslope drainage	N/A
Sediment loading potential	Soil erodibility of upslope drainage	N/A

Acronym definitions

Wisconsin Department of Natural Resources (WDNR) Wetland Water Quality Assessment Tool:⁴ This tool assigns a relative score to each catchment (HUC-14) based on the degree to which its wetlands protect downstream water quality by trapping sediment. The relative amount of sediment trapped by wetlands in each catchment is determined by using a sediment loading grid and P-8 model and the inputs listed below to calculate the relative sediment loading in each catchment multiplied by the wetland trapping efficiency. By adding wetland area to the input wetland map representing locations of potential wetland restoration projects, planners can estimate the relative increase in sediment trapping that can be gained in a catchment through wetland restoration.

Factor used in analysis	Data source(s)
DEMs	SEWRPC + county data
Hydrography	WDNR 24K Hydrolayer
Land use layer	SEWRPC
SCS runoff curve numbers	210-VI-TR-55, Second Ed. (1986); NRCS, WDNR, and SEWRPC (2004)
Unit area pollutant loads	Bannerman et al. (1894)
Wetland area	WWI + SEWRPC land use inventory
Catchment area	8-12 digit HUCs; 14 -digit catchments created for project
Long-term continuous rainfall/snowfall data for the region of interest	Regional dataset compiled by regional partners

Acronym definitions

Wetland Prioritization Study Main Page

¹Miller, N., T. Bernthal, J. Wagner, M. Grimm, G. Casper, and J. Kline. 2012. The Duck-Pensaukee Watershed Approach: Mapping Wetland Services, Meeting Watershed Needs. The Nature Conservancy and Environmental Law Institute, Madison, Wisconsin.
² Rivera-Monroy VH, Branoff B, Dortch M, McCorquodale A, Meselhe E, and Visser J. 2012. Nitrogen uptake model (potential for) technical report. Appendix D-22. Louisiana's Comprehensive Master Plan for a Sustainable Coast. Coastal Protection and Restoration Authority of Louisiana. Baton Rouge, LA.
³ Vanasse Hangen Brustlin, Inc. 2009. Merrimack River Watershed Restoration Strategy. Prepared for New Hampshire Department of Environmental Services.
⁴ Kline J, Bernthal T, Burzynski M, Barrett K. 2006. Milwaukee River Basin Wetland Assessment Project: Developing Decision Support Tools for Effective Planning.