Review of “Constructed wetlands for water quality improvements: Benefit transfer analysis from Ohio”

by N.B. Irwin, E.G. Irwin, J.F. Martin and P. Aracena

Bodies of water provide many benefits to residents through recreation and use but run-off from agriculture and urban areas can impair water quality. While Ohio has worked on improving water quality in its rivers and large streams, with 80 percent meeting aquatic life goals, less than 13 percent of its lakes meet such a standard. A possible solution to this problem is the construction of treatment wetlands to remove excessive nutrients from water bodies. Constructed wetlands utilize the natural environment as a form of water treatment and act as a filter to remove excessive nutrients and pollutants in runoff water.  Compared to other forms of water treatment, wetlands deliver water quality improvements with significantly smaller lifetime operation and maintenance costs.

This study examines the feasibility of using constructed wetlands to improve water quality in sample of 24 inland lakes from Ohio. Using water quality data collected from the Ohio Department of Natural Resources and the Ohio Environmental Protection Agency, data on population, housing prices and incomes from the U.S. Census, and information on recreational visitors, the total cost of creating and operating free surface water wetlands to improve water quality by 10 percent through the removal of phosphorous is estimated. Additionally, the study derives the willingness-to-pay for a 10 percent water quality improvements by both homeowners and recreation users. Nearby residents benefit from improved water quality through higher house prices while recreation users value the changes in water quality through an expansion of possible outdoor opportunities.

The total cost of constructing wetlands for all 24 lakes is over $107 million, with size and surrounding land cost for each lake differing greatly. The willingness-to-pay estimates for both the surrounding homeowners and recreation users averages over $606 million, depending on the model specification. The most conservative estimates indicate that constructed wetlands could provide a lifetime cost benefit ratio of 1:2.92 or a $2.92 return for every $1 invested. The average per capita benefit per resident or recreation user would be $68. These results indicate that wetlands are clearly an effective means of both reducing nutrient loadings in surface water and providing positive economic returns to homeowners and recreational users.

The study also examines the cost implications for constructed wetlands to be used as a strategy to meet hypothetical statewide standards for phosphorous concentrations in lakes at 50 µg/L and 25 µ/L per lake. At the lower standard of 50 µg/L the estimated cost is $870 million, whereas at the stricter standard of 25 µg/L costs would exceed $2.7 billion and require 0.5% of all arable land in Ohio. Using wetlands for achieved phosphorus reduction goals is not a cost-effective strategy. Instead, a comprehensive approach to nutrient reduction and water quality is necessary.

To read the complete article follow the link:


Summarized by Ben Brown, Program Manager: Farm Management Program

Leave a Reply

Your email address will not be published. Required fields are marked *