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GENERAL WATER - QUALITY CHARACTERISTICS OF STREAMS <br />Water quality of Fountain and Monument Creeks is affected by many natural <br />and manmade factors. Some of the general water - quality characteristics of the <br />streams can be described using information about water temperature, specific <br />conductance, pH, BOD dissolved oxygen, and suspended solids. <br />Water temperature is important because it affects the usefulness of water <br />for many purposes and partially controls physical, chemical, and biological <br />processes. Temperature affects the waste- assimilation capacity and, there- <br />fore, the aesthetic and sanitary qualities of water. Increased temperature <br />accelerates the biodegradation of organic material in overlying water and in <br />bottom deposits, thus increasing dissolved - oxygen demand (U.S. Environmental <br />Protection Agency, 1976, p. 220). <br />Specific conductance is an indicator of general water quality because it <br />is directly related to the concentration of dissolved solids in the water; as <br />dissolved solids increase, specific conductance increases. In the study area, <br />mountain streams have relatively small specific conductance because the <br />streams are in contact with igneous and metamorphic rocks that resist chemical <br />weathering. In contrast, streams of the plains are in contact with sedi- <br />mentary rocks that frequently contain soluble minerals, thereby resulting in <br />relatively large specific conductance. Specific conductance of streams also <br />is affected by man - related activities, such as irrigation and wastewater <br />treatment, as well as by soluble substances that enter the stream from runoff. <br />The pH is a measure of the hydrogen -ion activity and is important in <br />water - quality investigations because solubility of many chemical constituents, <br />including trace elements, and the biological activity of many organisms in <br />water are pH dependent. Thus, pH is an important factor in controlling con- <br />centrations of chemical constituents and populations of organisms in the <br />water. The pH also may affect the suitability of water for various uses. A <br />pH range of 6.5 to 9.0 is the numeric standard set by the Colorado Department <br />of Health (1982) for Fountain and Monument Creeks. <br />The BOD5 represents the quantity of dissolved oxygen required by orga- <br />nisms-in the stream for aerobic biochemical digestion of organic matter in <br />water (Klein and Bingham, 1975, p. 5) and is a useful way of expressing <br />stream - pollution loads. The rate of biochemical- oxidation reactions are <br />dependent on water temperature, microbial population, and waste type. The <br />BOD5 analysis is performed in a laboratory at a constant temperature of 20 °C. <br />The B0D5 is calculated from the dissolved - oxygen depletion that occurs over a <br />5-day incubation period. <br />Dissolved oxygen is another constituent of interest in water - quality <br />investigations. The dissolved - oxygen concentration in water is inversely <br />related to water temperature and is affected by photosynthesis, respiration, <br />physical interaction of the water with the atmosphere (aeration), and waste <br />loads. It generally has been considered significant in evaluating the aes- <br />thetic qualities of water as well as for maintaining fish and other aquatic <br />life. Therefore, the Colorado Department of Health (1982) established a <br />minimum standard of 6.0 mg /L for Upper Fountain Creek and 5.0 mg /L for Lower <br />Fountain Creek, Upper Monument Creek, and Lower Monument Creek. <br />18 <br />