Blue is good—i.e., the stream or lake meets the environmental standards for all of the activities the state's scientists say it should support (swimming, breeding fish, irrigation, etc.). Red is bad—the stream or lake exceeds the total maximum daily load (TMDL) of nitrates, phosphates, sediment, coliform bacteria, or other pollutants that the water body can handle safely and naturally.
Lake County sits atop a nicely blue spur of the Lower Big Sioux watershed. Lakes Herman, Madison, and Brant all check out, Category 1, good for all designated uses. Our lakes got rated for high "Trophic State Index" (that's high nutrients, high algae) back in 1999, and the DENR assigned us TMDL to work toward. Sounds like we're doing o.k.... so light work at our first county water quality committee meeting Thursday, right? ;-)
Actually, no. The majority of lakes in the state are still classified as eutrophic or hypereutrophic, thanks to ag runoff and soil erosion into our shallow lakes. Plus, the east fork of the Vermillion River isn't in such good shape; the stream that drains the county line between Lake and McCook has high fecal coliform concentrations—i.e., cooties from cow poop. Maybe I'll wait on that kayak trip....
Statewide, the draft report says two thirds of our streams fail to meet water quality standards for all of their designated uses. Lakes are in better shape, with one in five lake assessed failing to meet standards for all designated uses. In all, DENR plans to list 45 lakes as impaired and requiring TMDL development.
So where does this pollution come from? Well, in the lakes, as the Farm Bureau likes to say, Thank a Farmer™:
The major problems of South Dakota lakes continue to be excessive nutrients, algae, and siltation due to nonpoint source pollution (primarily agricultural). Although land-use practices have improved in many agricultural watersheds, internal phosphorus recycling continues to negatively impact the trophic state of many lakes. Aging reservoirs have also become more eutrophic as many are now approaching their expected life spans. Water quality degradation due to acid precipitation, acid mine drainage, or toxic pollutants, is presently not a problem in South Dakota lakes [DENR, draft 2010 Integrated Report, p. 50].
Fecal coliform bacteria from ag operations and from wildlife cause problems in the largest portion of impaired South Dakota streams, followed by suspended solids (silt from erosion) and E. coli.
So on the good side, we don't have a lot of chemical industrial pollution, although I suspect frequent reader Mr. Kurtz can tell us a thing or two about the impacts of mining in the Black Hills. The draft report also notes that DENR has started water monitoring in Union County to get baseline data that will allow us to assess the impact of the Hyperion oil refinery (or the Hyperion landfill, or whatever comes first).
But we've got plenty of work to do to address the problems caused by our #1 industry, agriculture. More grassy waterways, more conservation acres, more erosion control—let's keep working to turn more of that map blue!