Roaring Fork Stream Flow Survey (2)

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However the real time stream gages in the basins do not commonly have a lengthy historical record. The length of record for 12 of the real time gages is: 4, 6, 7, 15, 24, 25, 39 (2), 40, 41, 48, 61, and 96. Ruedi Reservoir and Fryingpan-Arkansas Project, which impact the Fryingpan River, were operational around 1968 while diversions from the Roaring Fork River through the Twin Lakes Tunnel began in 1935. Only the stream gages at Crlenwood, North Fork Fryingpan River near Norrie and the Fryingpan River at Meredith have the suggested 20 years pre-impact record to support 1HA. Additionally impacts on systems such as the Crystal River Basin did not occur at one point in time. The first step in using the IHA, is to identify the most appropriate indicators for each subbasin. Olden and Poff (2003) recommended these IHA parameters for snowrnelt-dominated systems. They suggested using them in conjunction with more intuitive index selection criteria based on the particular ecological question of interest and in order of the largest absolute loadings on each statistically significant principal component. PC I (88.7% variation explained) Code Hydrologic index MA29 Variation in June flows MA12 Mean January flows MA13 Mean February flows MA14 Mean March flows MA23 Mean December flows DLS Annual minima of 90-day means of daily discharge duration RAl Rise rate next RA3 Fall rate I)e~nition Coefficient of variation in June monthly flows Magnitude of minimum annual flow of 90-day Mean rate of + change inflow from one day to the Mean rate of -change in flow from one day to the next DL1 Annual minima of 1-day mean of daily discharge Magnitude of minimum annual flow of 1-day duration DL2 Annual minima of 3-day means of daily discharge Magnitude of minimum annual flow of 3-day duration DI14 Annual maxima of 30 day means of daily discharge Magnitude of maximum annual flow of 30-day duration Dx5 Annual maxima of 90 day means of daily discharge Magnitude of maximum annual flow of 90-day duration PC II (5.3% variation explained) DL16 Low flow pulse duration mean duration of FLl FLl Low flow pulse count-Number of annual occurrences during which the magnitude of flow remains below a lower threshold. Hydrologic pulses are defined as those periods within a year in which the flow drops below the 25a` percentile (low pulse) of all daily values for the time period.