As other regions of the country struggle to find adequate supplies of clean water, Maine has abundant, and comparatively clean, water resources.

Maine’s water is approximately 20 percent to 60 percent cleaner than lakes and streams in the rest of the United States, according to the 2015 “Measures of Growth” report by the Maine Economic Growth Council and Maine Development Foundation.

Our lakes and streams support our recreation and tourism industries, and they are home to vibrant fish and wildlife populations. Clean water improves the value of lakefront and riverfront properties, and reduces the need for costly treatment of drinking water.

There are some causes for concern about the cleanliness of Maine’s waters, however.

Water clarity is measured by a Secchi disk, a black and white circular disk that measures the depth at which a person can no longer distinguish between the two colors.  Water clarity in several Maine lakes has been declining since 1998, possibly due to changes in land use, temperature and more heavy rainfall events.

Water clarity, which measures how far light can penetrate into a water body, is not the only factor in gauging water quality, but it is a relatively easy way to assess changes in the water body over time. Going forward, water quality may be threatened by a changing climate and by recreationists (such as by powerboating), property owners  (such as by fertilizing lawns and not maintaining septic systems) and industry (such as by agricultural runoff and tourist activities).

Lake water

A reduction in water clarity, and potentially water quality, poses significant challenges.

For example, a two-meter decline in Sebago Lake’s water clarity since 1998 is likely to translate into tens of millions of dollars in lost economic value through declines in local property values, the quality of recreation experiences, and aesthetic values (e.g., loons and other wildlife are negatively affected by decreased water quality).

Dirtier water could hurt home property values, perhaps by as much as 15 percent, according to a study on China Lake by the University of Maine and the Maine Department of Environmental Protection. The study found that a continued decline in China Lake’s water quality in could depress property values by as much as $24 million.

Sea water

While Maine’s lakes and streams rank very high for water quality, our coastal beaches rank 27 out of the 30 states that are either on a coast or on the Great Lakes, according to the Natural Resources Defense Council.

Although the state and federal measurement systems vary and do not allow for direct comparisons, and Maine’s beaches are monitored more frequently than other states, water quality along our beaches is a significant concern.

Water pollution is especially troubling in or near population centers and when the source of the pollution is closer to the problem area.

Coastal water quality is essential to Maine’s shellfish industry. The Maine Department of Marine Resources may close shellfish flats based on cleanliness and harvesting status, heavy rainfall and flooding, and toxic algal blooms.

Closures result in significant financial losses for harvesters and wholesalers, especially in the summer. A 2008 report estimated a $3.4-million loss in sales for Maine businesses and a $1.75-million loss in income for Maine residents from a hypothetical one-week coast-wide shellfish flat closure in August.

Maine’s rugged environment and natural amenities are an important component of our identity, image, and brand. Our water quality helps support a vibrant tourism industry and recreational opportunities, contributes to our economy and property values, and saves us money on costly water treatment.

It is important that we continue to protect this critical asset.

Mario Teisl is a professor and director of the School of Economics at the University of Maine. Kate Warner is an ecology and environmental science PhD student at the University of Maine.