Washington D.C. [USA], Dec. 4 : A team of researchers has found that reducing agricultural land immediately surrounding lakes and streams can improve water clarity by limiting nutrient runoff.
The article has been published in the journal Ecological Applications. A study of more than 5,000 Wisconsin lakes, shows that nearly, a quarter of them have become murkier in the past two decades.
It also shows this trend could get worse as a changing climate leads to increased precipitation. Researchers from University of Wisconsin-Madison in the US revealed limiting farming to 10 percent or less of the so-called riparian buffer zone-- vegetation immediately adjacent to a body of water-- around a lake and the streams flowing into it can improve water clarity.
"In the face of increasing precipitation, this analysis provides empirical support for the fact that adapting our landscape is going to be important into the future," said study's co-author Monica Turner.
Implementing such actions also benefits farmers, as they suffer less damage to their croplands during heavy rains, Turner says.
Using more than 25 years of data collected by citizen scientists, the DNR and the federal government, the researchers analyzed Wisconsin's lakes to identify not just trends in water clarity (an indicator of lake health) but also how the landscape and the climate interact to determine year-to-year fluctuations.
While their results show water clarity in the majority of lakes has not changed and six percent of lakes are on an upward trend, the fact that more lakes are getting worse signals there is work to be done.
"If we want to maintain or improve water clarity, we need to think about trends in precipitation," said lead author Kevin Rose from Rensselaer Polytechnic Institute in New York.
The study shows that wet years (like the current one) can be especially hard on lakes that typically have greater water clarity, like those found in northern Wisconsin.
Clear lakes are more sensitive to the onslaught of nutrients and plant matter flushed in by the rain, which can cause water to turn murky, brown and green.
Mitigating the negative impacts of more rain, however, will require managing land in ways the research team did not expect.
While the results indicate broad-scale land use does matter during dry years, the opposite is true in years with higher precipitation, when water clarity is more dependent on how the land is managed in particular places.
"Namely, riparian areas with less agriculture fare better and can play a significant role in reducing nutrient runoff," Rose added.
"This study provides on-the-ground evidence that is consistent with what our computer models are telling us," says Turner, referring specifically to model results produced by the Water Sustainability and Climate Project at UW-Madison.