| Forest cover and its effect on water treatment costs
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Forest cover and its effect on water treatment costs

It’s common knowledge in the water sector that as forest cover increases, turbidity decreases.

But a new study by AWWA’s Source Water Protection Committee takes that understanding a step further, showing that forest cover lowers the cost of treating water by improving water quality at the intake. Conversely, reducing forest cover through development, fire, or other natural disasters, increases chemical treatment costs. 

“These results imply converting 10 percent of the watershed from forest cover to developed area increases chemical treatment costs by 8.7 percent, which would be an annual increase of over $65,000 for the typical treatment plant in this study,” the report notes. Those figures are an average of the treatment plants studied, and do not necessarily reflect what any one particular plant would save. 

The 35-page report, titled “Effect of Forest Cover on Drinking Water Treatment Costs,” bolsters previous research that a healthy watershed trims treatment costs. It notes that many factors impact an individual plant’s chemical treatment costs, including the type of filtration and disinfection used. 

The project was funded by AWWA’s Technical & Educational Council and the U.S. Endowment of Forestry and Communities, and will be available soon on AWWA’s website. 

Robert Morgan, PhD, immediate past chair of the Source Water Protection Committee and a co-author of the report, said the findings will lead utility managers to ask themselves a key question: “Can I afford to spend money to improve my forested watershed and can I recoup that money through reduced treatment costs?’

“If I maintain my forest at the point it is now, I’m not reducing my costs, I’m just preventing them from going higher because of reduced cover in the watershed. It’s a voided cost rather than a cost reduction.”

Morgan said the forest cover findings should be viewed in the larger context of the value of source water protection. 

“While the study indicates relatively small savings, it is one piece of the large pie of the economic benefits of source water protection,” Morgan said, “which would include improving life cycle costs through the delay of treatment improvements and associated environmental and societal benefits.”

The report, which also includes utility case studies, is based on results of a 2014 AWWA survey of 37 treatment plants located in forested areas.  Of those, 26 used conventional treatment, seven used direct filtration, two used advanced treatment, and two had no treatment except disinfection.

Forested lands are the source of more than half of the surface water supplies in the continental United States and provide drinking water to about 212 million Americans, through public and private water systems, according to the report. 

Nearly all of the country’s forests are facing pressures from urbanization and agriculture, which are expected to result in even greater forest fragmentation.

“This loss of forests is diminishing the landscape’s ability to provide key ecosystem services, particularly services related to the provision of safe drinking water,” the report reads.

According to the report, the cost of chemical treatment averages $105.3 per MG among the study participants, which is similar to the average reported in other studies. A turbidity increase of 1 percent increased chemical costs by 0.19 percent, the report notes.

Chi Ho Sham, PhD, and past chair of the Source Water Protection Committee, said the idea for the project dates to October 2012 when Travis Warziniack, PhD, of the U.S. Forest Service Rocky Mountain Research Station, approached AWWA to explore collaboration opportunities to assess “the role and value of rural lands in urban drinking water supply.” 

Warziniack is an economist and is interested in estimating the economic values of watershed protection to drinking water supplies.

The final project report includes case studies for Central Arkansas Water and Eugene Water and Electric Board in Oregon.

For Central Arkansas Water, the water quality of Lake Maumelle is very good, but has degraded slightly over the past two decades, according to the report. Chlorophyll, a total organic carbon, and turbidity all increased between 1994 and 2014.

“Without proper land use management in the watershed, future water quality conditions would exceed source water quality criteria that could threaten public health and/or require costly added treatment,” according to the report.

At Eugene Water and Electric Board, their comprehensive Drinking Water Source Protection Program was developed in 2001 to address multiple threats to the McKenzie watershed from urban runoff, agricultural activities, forest management activities, hazardous material spills, development and septic systems.

EWEB's program involves engaging with McKenzie watershed landowners and stakeholders using voluntary approaches. EWEB spends more than $700,000 annually on its source protection program, which includes 2.75 staff. 

“EWEB’s source protection staff is working with management to enact a watershed stewardship fee on the utility’s bill to provide a more predictable and sustainable source of funding for source water protection going forward,” the report notes.

The report concludes by noting that forests yield far more than safe drinking water.

“Additional benefits would accrue from enhancements in wildlife habitat and recreation opportunities,” the report notes. “The results of this study should be taken as a lower bound for the value of forest protection.”