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6. The Land and Geological Factors
- University of Arkansas Press
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CHAPTER 6 The Land and Geological Factors To a person who is not a scientist, a lake might appear as nothing more than a large puddle of water. Under the wrong conditions, and with enough pollution, it could seem to take the form of a lagoon or a cesspool. The truth is much different. A lake’s formation, its years of geology, and its recorded limnology—or the study of bodies of freshwater— reveal that a lake is actually a dynamic phenomenon or creature. “Limnological characteristics of large reservoirs differ to some extent from those of natural lakes as a result of human input in the form of regulation of water levels for flood control and power generation,” states an environmental assessment of the Lake of the Ozarks prepared in 1982 by the US Army Corp of Engineers.1 It also was noted in the assessment that “lowest pools usually occur during winter. Filling generally occurs during the spring months via precipitative runoff from the watershed. During summer, water may be withdrawn for power generation or for flood control.” Beneath the darkness lurks a world dependent on a symbiotic relationship between the water and its contents, as well as the living plants and animals that call it home. The structure of lakes can be described as layered, such as a forest ecosystem. A lake that is a reservoir has other variables by way of damming; its health and water quality are at the mercy of the officials who control the release of water. A variety of life-dependent components are needed to keep a lake thriving. Among them are light and a lake’s watershed health, including what development is around the body that might influence erosion and pollution.2 As for light, the further the sun penetrates through the water’s depths the more plant-life processes called photosynthesis can occur, and thus the more life the water can sustain whether in the form of algae or aquatic plants. A lake’s watershed often holds the ingredients for its health: Good stuff, such as dissolved oxygen from the atmosphere and plant life native to the area, along with the bad, such as sediment from erosion, nutrient pollution from fertilizers, and harmful and improperly managed wastewater spilling from parking lots and pavement. Rainwater that drains down from surrounding land into the lake can bring with it other concerns , such as the E. coli–tainted soil that is washed into the Lake of the Ozarks after heavy rains. This runoff affects what is known as the lake’s chemistry. Pollution can mean heavy metals or certain toxins are flushed into the waterways and can create havoc for the living things there.3, 4, 5 Even getting past the disgusting thought of sewage and potentially harmful bacteria that accompanies it, there can be problems with the nutrients the sewage contains. Sewage contains a much higher concentration of phosphorus, which can prompt algal growth. Density of the algal blooms suffocates other plants and fish and causes changes in the aquatic ecosystems. A lake’s geology can be one of the biggest indicators of its health and future water quality. It is affected by everything that surrounds it. Any addition of outside sources in the form of pollution or sewage can change its chemical and physical makeup. For the Lake of the Ozarks, the topography makes it easier for the lake to be polluted. That topographical culprit along the lake’s watershed is known as karst. This type of landscape accounts for 10 percent of the earth’s surface and is distinctive because the rock that forms the landscape (mostly dolomite, which is like limestone) can dissolve as the surface water meets the rock. Cracks grow larger. Crevices expand. This process of breaking down rocks, usually limestone or dolomite, accounts for the many sinkholes and caves that are common within the Ozarks. The sinkholes take on the role of a funnel and deposit the water directly into the area’s water supply.6, 7 This characteristic, though, also means that the ground and rock 58 THE LAND AND GEOLOGICAL FACTORS [54.198.154.234] Project MUSE (2024-03-29 09:52 GMT) loses its natural filtering dynamic and that any polluted surface water flowing over the karst area can easily penetrate the soil. The groundwater is replenished or recharged in two different ways. One is through rain and other forms of precipitation, which gradually finds its way to a spring or water source. The...