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US Army Corps Reservoirs Most of us are familiar with the larger lakes in Missouri -- Harry S Truman, Smithville, Table Rock -- but what else do you know about them? Did you know there are five US Army Corps of Engineer Districts ( Kansas City, St Louis, Little Rock, Memphis & Rock Island) that oversee most of these larger lakes? I’m sure your next question will be “why does it take five Corps Districts to cover the Show-Me State?” I have a very good answer – for Civil Works and Regulatory purposes, the Corps boundaries correspond to watersheds! The Kansas City District is responsible for 7 lakes within Missouri – Stockton, Pomme de Terre, Harry S Truman, Long Branch, Smithville, Longview, and Blue Springs. In addition to these lakes, the Kansas City District is responsible for 9 lakes in Kansas (Hillsdale, Pomona, Melvern, Clinton, Perry, Tuttle Creek, Milford, Kanopolis, and Wilson); Harlan County Lake in Nebraska; and Rathburn Lake in Iowa (see the figure below). These lakes differ greatly in surface acreage (700 – 55,000 acres), watershed size (21,000 – 16,000,000 acres), age (20 – 60 years), flushing rate (0.2 – 2.4 years), water quality, fishing quality, and recreational use (see the Table below).
The best water quality is associated with the Ozark border watersheds (Pomme de Terre and Stockton), but what is responsible for the measured differences between lakes? The primary factor impacting water quality is land use within the watershed. The amount of pollutants (like sediments and nutrients) that are transported to lakes and streams via runoff is directly related to land use in the watershed. This has been discussed in prior issues of ‘The Water Line’, as well as the scientific literature (Jones et al. 2004). Geology is another factor, due to differences in rock and mineral composition as well as soil type. Some differences in water quality between lakes can be explained by ecoregions. According to EPA, “Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources. They are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. By recognizing the spatial differences in the capacities and potentials of ecosystems, ecoregions stratify the environment by its probable response to disturbance.” Some water quality standards and future nutrient criteria are set by ecoregions. Now that we’ve discussed these factors, here is a trivia question for you to ponder (answer is listed at the end of the article) – “What is the clearest lake in Kansas?” What are the immediate threats to water quality in these lakes? Sedimentation would be the single greatest threat because it reduces storage capacity, transports excess nutrients, and impacts recreational use / fishery. As mentioned, nutrients are a huge concern because they impact the overall productivity (eutrophication), increase the threat of blue green algae blooms, reduce depth of stratification and water clarity. Excess nutrients impact drinking water supplies (costs and availability), the fishery, and recreational use (aesthetics). Herbicides represent yet another water quality threat and this is primarily as a drinking water concern. Bacterial contamination is a growing threat to both drinking water supplies as well as recreational use (boaters and swimmers). To protect the water quality of these valuable aquatic resources, we need to develop active watershed partnerships. Such partnerships need to include all stakeholders – landowners, recreational interests, cities, counties, and state and federal agencies. For more information on US Army Corps of Engineers lakes within the Kansas City District, please visit http://www.nwk.usace.army.mil/.
References: Answer: Wilson Lake. The watershed is dominated by grassland with very limited row crop farming or urban presence, and the geology is dominated by sandstone. Steve Fischer, USACE - KC District |
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