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0093 Monument Creek Between 1975 and 1983, water temperature, specific conductance, pH, BODs, dissolved oxygen, and suspended solids were measured at four sites on Monument Creek. The period of record of water-quality data varies at each of the four sites (table 2). Water temperature, specific conductance, pH, and dissolved oxygen were measured monthly at each site when water-quality samples were collected. Additional measurements of water temperature and specific con- ductance were made at sites M10 and M28 (fig. 1) when streamflow measurements were made. Water Temperature Measurements of instantaneous water temperature in Monument Creek are summarized in figure ]9. At site M]O, water temperatures have ranged from o to about 25 DC, and more than 75 percent of the measurements were less than 20 DC. Coldest water temperatures measured at site M]O (fig. 20) have occurred during the winter; median temperatures measured during December, January, and February have been 1.5, 1.0, and 1.5 DC. Warmest temperatures have occurred during July; median water temperature was ]9.5 DC. Downstream from site M28 (fig. ]9), instantaneous water temperatures ranged from 0 to 30.5 DC. Coldest temperatures measured at site M28 (fig. 20) occurred during the winter; median temperatures measured during December, January, and February have been 0, 0, and 1.5 DC. Warmest temperatures occurred during July; median water temperature was 23 DC. Specific Conductance Specific conductance of Monument Creek increases downstream as the stream flows from the mountains through residential, commercial, and industrial areas (fig. 21). Measurements of specific conductance at site M]O have been small because the streamflow consists of water that largely is unaffected by man and drains a part of the Rampart Range, which is composed mostly of igneous and metamorphic rocks that resist chemical weathering. Measurements of specific conductance made at site M]O have ranged from 50 to 250 ~S/cm; median specific conductance was 180 ~S/cm. Downstream from Monument, the stream is in contact with sedimentary rocks that contain soluble minerals and receives water from wastewater-treatment plants, ground-water discharge, and tributaries that drain densely urbanized areas. As these waters enter Monument Creek, specific conductance increases. The increase in specific conductance that occurs between site M28 and the mouth of Monument Creek probably results from drain- age of the commercial and industrial areas of Colorado Springs. The apparent decrease in specific conductance between site M34 and site M35 probably is the result of different periods of records having different sources of flow (fig. 2]). The range of specific-conductance measurements at the four sites on Monument Creek increases downstream because of greater variations in flow and differences in sources of flow. 33