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<br />Memorandum To: File <br />Page 7 <br />September 28, 2001 <br />Table 4 <br />Statistical Analysis of Simulated versus Historical Daily Flow at USGS Gage 09241000 <br /> Mean <br /> Mean Error % Std Dev of <br /> Daily Flow (acre-feet) difference Error <br /> (acre-feet) <br />Historical 633.9 <br />Average 632.3 1.514 0.24% 416.7 <br />Dail <br />Daily 632.4 1.489 0.23% 47.4 <br />Pattern <br />Daily <br /> 632.3 1.549 0.24% 47.3 <br />In ut <br />Future scenario models <br />The scope called for Boyle to also compare the results of future simulations with each of the daily <br />models, both to each other, and to the USFWS method. In the USFWS method, the monthly model is <br />executed, and simulated monthly results at a gage are distributed to daily values using the pattern of <br />the historical gage. <br />The models all include an instream flow requirement of approximately 130 of/day at the Clark gage. <br />The instream flow right is senior to NewDemand, but junior to all other demands in the basin. When <br />modeled flows are at 130 of/day, the instream flow right is the calling right and NewDemand is at <br />least partially out of priority. Conversely, when modeled flows are above 130 of/day, NewDemand is <br />being fully satisfied. Understanding this, one can observe the following from Figures 8, 9, and 10, <br />which depict USFWS method, Average Daily, Daily Pattern, and Daily Input future scenario results <br />for 1977, 1983, and 1988: <br />As in the calibration models, the Average Daily hydrograph exhibits discrete "jumps" either <br />when the month changes (and a different amount of baseflow is available), or when New <br />Demand changes. Modeled flows never reach peak daily flows because the monthly average <br />baseflow is always lower than the peak. On the other hand, Average Daily model flows <br />sometimes exceed flows in the other models, as in May of 1983 (Figure 9). During this <br />month, the historical hydrograph rose sharply in the second half of the month (see Figure 3; <br />historical hydrographs are not included in the future scenario figures because they are <br />different in scale), raising average available flow for the month well above the combined <br />demands of all users. As a result, NewDemand and all other demands are met throughout the <br />month in the Average Daily model. An analogous effect for the falling limb is apparent in <br />July. <br />2. The Daily Pattern and Daily Input models show more realistic results on a daily basis. In the <br />future scenarios, there i$ water above the minimum instream flow amount only when <br />available water modeled under historical conditions exceeds the sum of the instream flow <br />right and NewDemand. During early May, 1983, NewDemand is at 1200 of/day and the <br />TaskMem2Final.doc I304'CE <br />