Water Quality of Fountain and Monument Creeks

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The streamflow of the northern part of Lower Fountain Creek has been gaged at sites F17 and F27 (station 07105800 Fountain Creek at Security) (fig. 1) and is summarized in figures 4 and 5. Generally, streamflows at sites F17 and F27 are smallest during fall and winter (fig. 4); larger stream- flows occur during spring from snowmelt runoff and during summer from thunder- storms. The streamflow- duration curves shown in figure 5 indicate that mean daily streamflow has been less than 28 ft /s at site F17 and has been less than 45 ft /s at site F27 about 50 percent of the time. The slope of the curves indicates that the streamflow varies substantially, and flow is largely from runoff. Except at extreme streamflows, figure 5 also indicates that instantaneous streamflow measured when water - quality samples were collected compares favorably with the frequency distribution of mean daily streamflow at site F17. Therefore, water - quality samples collected at site F17 should characterize the water - quality conditions that occur approximately 98 percent of the time. Downstream from the town of Fountain, streamflows vary considerably from the northern part of Lower Fountain Creek due to numerous diversions for agricultural use. Except for Pueblo, the remaining 30 mi of stream traverse irrigated agricultural lands. Periods of no streamflow have occurred during the summer months of many years. Water enters the stream as irrigation- return flow, ground -water discharge, and from ephemeral tributaries that predomi- nately drain rangelands. Streamflow downstream from Fountain has been gaged at site F53 (station 07106300 Fountain Creek near Pinon) (fig. 1) and site F66 (station 07106500 Fountain Creek at Pueblo); streamflow at these sites is summarized in figures 6 and 7. Streamflows are much larger during the winter at sites F53 and F66 than in the northern part of Lower Fountain Creek due to lack of winter diversions for irrigation. The largest flows in the southern part of Lower Fountain Creek occur during the summer as a result of thunderstorms. However, during dry summers when irrigation demands are large and runoff is small, Fountain Creek may be dry at sites F53 and F66. The streamflow- duration curves shown in figure 7 indicate that streamflows vary substantially and are greatly affected by direct runoff and upstream diversions. The mean daily streamflows are less than 41 ft /s at site F53 and less than 17 ft /s at site F66 about 50 percent of the time. Frequency curves of instantaneous stream- flows made when water - quality samples were collected at sites F53 and F66 are considerably different than the mean daily streamflow- duration curves (fig. 7). Therefore, the summary statistics of water - quality constituents measured at sites F53 and F66 that are affected by streamflow may be somewhat biased toward larger streamflows. Upper Monument Creek Upper Monument Creek comprises approximately a 3 -mi stream segment down- stream from the national forest boundary and U.S. Defense Department property to the outlet of Monument Lake, which is located at Monument (fig. 2). This stream segment has been classified for class 2 recreation, class 2 warm -water aquatic life, domestic water supply, and agricultural uses. Numeric water - quality standards associated with these classifications are listed in table 1. 10