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Table 3.1. Optimized parameter valuesa for the upper and /ower subwatersheds of Mill Creek (after Shih et ai, 1976). Value Mill Creek Parameter Description Upper Sub. Lower Sub. Neff's watershed watershed Can on SFC Field capacity of soil inches) 6.00 4.5 5.0 TBF Base flow decay conslant (day-!) .004 .006 .005 GLL Ground water slorage level above which sub-surface 4.8 5.0 5.0 outflow occurs (inches) TGW Inlerflow decay conslant (day-!) .04 .025 .03 QK The fraction of outflow from soil moisture that be- .15 .26 .20 comes inter flow SMR Snow mell rate (inches/day F) .11 .07 .07 RTF Evapolranspiration faclor .59 .45 .50 TAUSW Surface runoff decay constant (day'!) .30 .50 .50 SI Upper limil of interception slorage (inches) .40 .60 .40 FC Minimum value ofinfi!tration (inches/day) 2.0 1.0 1.0 DKT Infiltration decay constanl 2.0 1.5 1.5 SS Salurated soil level (inches) 12.8 13.5 13.0 WILT Wilting point of the soil (inches) 1.0 1.5 1.0 ROS Faclor relaled 10 snow melt. by rain .01 .01 .01 TRAIN Temperature above which all precipitation falls as rain 35.0 35.0 35.0 CPF Channel precipilalion factor .003 .003 .003 FNGM Factor related to ground melt in snow pack .02 .023 .02 TFWFN Decay conslant for drainage of free water from snow .10 .18 .15 pack (day-!) Mean value of Ihe objeclive function (inches per unit area) 1.53 3.24 NA Mean annual stream flow (inches per unit area) 6.97 10.15 NA Ratio of mean objective function to mean annual streamflow .22 .32 NA a Parameters are shown in decreasing order of sensitivity. The transfer of parameter values from one walershed to another is not an ideal procedure but can be used when one has no other suitable runoff records for calibration. Factors favoring this meth- od in this case are listed abov.~; however, there are differences in the geology of the Mill Creek and Neff's Canyon watersheds. Some information on these differences (taken by Calvin G. Clyde (i 974) in a geology class some years ago at the University of Utah) is sununarized below. In 1948, some measurements were made by Salt Lake County of water flow rates from Neff's Canyon. A geologic survey of the canyon at that time also indicated the presence of glacial moraine and two faults. The Mt. Olympus Spring Company had submitted an application to direct water from Neff's Canyon, and County officials were concemed thai perhaps these waters supplied the Spring Creek, Castro. and Dry Creek Springs which are siluated on Ihe lower slopes of Mt. Olympus above the ur- banizing area of Ihe cove. In 1950 three students from the University of Utah discovered a cave in Neff's Canyon. It. was found that the limestone cav- ern exlended a distance of 1,170 feel from the por- tal to a point where water blocked Ihe way. It was speculaled that this water leaves the sire am bed al the fault lines and flows through the cavernous lime- slone to the three springs mentioned above. To confirm this speculation, dye was placed in the waters :of Neff's Canyon at a point upslream from the faull lines. This dye appeared at the springs 27 hours later and persisted for four days. Duting the spring runoff period of 1948 the lotal surface discharge from the Neff's Canyon drainage was measured at 330 acre feel per square mile. It was eslimaled that if the flows from the three springs during lhis sarne period were added to this figure, the total runoff from the watershed would be 1,800 acre feet per square mile. This figure is consistent with precipita- tion on the watershed during the winter of 1948 as estimated from snow survey data. On the basis of the geologic differences be. tween the Mill Creek and Neff's Canyon watersheds the unit surface runoff might be expecled to be less from Neff's Canyon Ihan Ihat from Mill Creek, all other factors being equal. For this reason, the parameters on Table 3.1 for Neff's Canyon might overestimate the surface runoff from the walershed. 31