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16000 14000 1-20%. 50% - 80% I 12000. ~10000 00 u. ~ ~ 8000 o ...J U. 6000. 4000. 2000 o 10/01 11/01 12/02 01/02 02/02 03/OS 04/OS 05/06 06/06 07/07 08/07 09/07 DATE Figure 2. Hydrographs for 80% (low), 50% (median) and 20% (high) exceedance flows for the Glenwood Gage between 1966 and 1994 (29 years). Hydrographs for the Glenwood and Cameo gages for low (80%), median (50%) and high (20%) years are given in Figures 2 and 3. These hydro graphs were developed from 63 years data (1934 to 1996) for the Cameo gage, and from 29 years data (1966 to 1994) for the Glenwood gage. Flow values were arranged from highest to lowest for each day of the year. For Cameo with 63 years of flow records, the 31.5 ranking record is the 50% flow, the 12.4 and 48.6 ranking records represented the 20% and 80% values, respectively. All 20%, 50% and 80% daily flows were plotted to create an annual hydrograph. Total water volume at Cameo is 1.79 million acre feet (MAP) for the low (80%) flow year, 2.59 MAP for the median (50%) year and 3.71 MAP for the high (20%) flow year. The minimum flow for the 80% exceedence (low) year is 1,140 cfs at Glenwood and 1,160 cfs at Cameo. Peak flows typically occur in late May in low years and early June in high years. The peak flow for the median flow year is about 14,000 cfs. Bankfull flow, defined as the flow that controls structure of alluvial channels, has an average recurrence interval of 1.5 to 2 years (Gordon et al. 1992). The 1.5 and the 2 year recurrence interval flows, based on 61 years of flow records (1934 to 1994), are 15,167 and 18,200 cfs, respectively (Appendix I, Table 1). Because of recent flow and channel modifications, a bankfull flow as defined by flows since 1934 (15,167 cfs) may not have equivalent channel forming properties as was the case under natural conditions. 4 I I I I I I I I I I I I I I I I I I I