Local environmental officials will soon learn the volume of nutrients polluting Lake Rhodhiss and where those nutrients are coming from.
With that data, they can figure out how to reverse the problem, which put the reservoir on a federal impaired waters list in 2006.
Lake Rhodhiss provides drinking water to Granite Falls, Lenoir, Morganton and Valdese and, indirectly, Hickory, because water flows into Lake Hickory from Lake Rhodhiss. The watershed Lake Rhodhiss drains is the largest in the Catawba River system of lakes – more than 450,000 acres.
The nutrient levels sometimes cause taste and odor problems in drinking water and could also hurt the health of fish there. Lake Rhodhiss is one of the best spots for bass fishing in the region.
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Depending on which sources are contributing the largest amounts of nutrients, cities' sewer treatment plants could have to spend more money to cut the source of those nutrients from their discharges.
After Lake Rhodhiss took on impaired status, environmental officials started working together to address the problem locally rather than waiting for the state to tell them what to do. Through the nonprofit Hickory-based Carolina Land and Lakes, they won grant money to study the pollutants and to figure out the problem.
Based on water sampling, officials believe excess phosphorous is the culprit, causing elevated nutrient levels and algae blooms that feed on the nutrients. The algae blooms then die, pulling oxygen from the water, which can potentially harm fish and sometimes cause a musty taste and odor in drinking water supplies.
Water test results that will reveal the quantity of nutrients and their major sources, whether urban or agricultural or both, are expected in July. Then officials can work with water suppliers, farmers and homeowners to reduce nutrient levels.
Project leader Jack Huss, a retired water resource professor and board member of several environmental groups, suspects that municipal sewer plants and field nurseries are the biggest contributors of nutrients to the lake.
Local Soil and Water Conservation District and N.C. Cooperative Extension officials have already been working with nurseries to reduce water runoff. Federal law would require sewer plants to cut their discharge if they're found to contribute high levels.
“The municipal people like to say it's not wastewater treatment plants” that contribute nutrients, Huss said. “And, of course, right quick, the agricultural people say it's wastewater treatment plants. By this study we're doing, we'll have hard numbers and people will have to say, ‘Yes, we have a role in this.'”
Project officials say they hope to get more grant money to reduce nutrients but caution that their work will take time.
“This didn't happen overnight,” said Tony Gallegos, water resources administrator with the Western Piedmont Council of Governments in Hickory, which is helping plan the project, “and it won't be turned around overnight.”