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<br />Otl?2?3 <br /> <br />,/ <br /> <br />.:,~ <br /> <br />,.,', <br /> <br />Category 2 includes parameters distributed by HRU's in a particular <br />drainage basin (table 2). These parameters are determined from the physical <br />characteristics in a particular HRU. To transfer values, data for these <br />parameters can be .obtained from aerial photographs, maps, or from direct <br />observation of soils and vegetation in the drainage basin. <br /> <br />,..,',> <br />......' <br />~~~: <br /> <br /><::{ <br /> <br />Category 3 includes parameters distributed by subsurface or ground-water <br />reservoirs. These parameters affect the timing and quantity of simulated <br />streamflow and indicate the flow paths of the various sources of streamflow <br />(for example, surface water or ground water). In ungaged drainage basins, <br />value~ of these parameters may be difficult to obtain. In gaged drainage <br />basins, values of these parameters can be derived mathematically from the <br />hydrograph. <br /> <br />;:.:;.;:; <br />\:;\'~ <br />;;:;':~~; <br />W~:: <br />,.,;:'~~, <br /> <br />. ".' <br /> <br />v'.'/: <br /> <br />,;.,."; <br />,:",'::-, <br />~".~; <br /> <br />In each region, an analysis was done using PRMS for the two basins to be <br />calibrated. Following analysis, the parameters that were indicated as most <br />sensitive were then optimized to obtain the best fit of simulated to observed <br />streamflow. After calibration, these optimized parameters were used for <br />verification. <br /> <br />,:f <br /> <br />.~~ <br />, ':'1~; <br />;':'::,'::':: <br />lii <br />~;~j <br />,'",,'..,. <br />'t~~;~;i <br /> <br />~ <br /> <br /> <br />ijf"~ <br /> <br />~~;i: <br />riJ <br /> <br />,'-",-'; <br /> <br />To enable calibration and verification, the period of record for each <br />drainage basin was divided into two parts. The first part was used for <br />calibration, and the second part was used for verification. In all of the <br />drainage basins except Hubberson Gulch, the total period of record included <br />water years 1976-81. In all basins except Hubberson Gulch, water year 1976 <br />was used as an initialization period, water years 1977-79 were used as the <br />calibration period, and water years 1980-81 were used as the verification <br />period. For streamflow-gaging station Hubberson Gulch near Hayden (09244464), <br />data were available for only 3 water years. Because of the short period of <br />record, no initialization period was used, and water years 1979-80 were used <br />as the calibration period and water year 1981 was used as the verification <br />period. <br /> <br />The third drainage basin in each hydrologic region was not used for <br />calibration and verification. These drainage basins were used to evaluate <br />the error that resulted from transferring the model parameters to a nearby <br />drainage basin. Parameter values for these drainage basins were obtained from <br />the calibrated drainage basins, and the specific methods used in transferring <br />these parameter values will be described in the "Assessing Transferability of <br />Model Parameters" section of this report. <br /> <br />('3?;' <br /> <br />I <br /> <br />C,'''''_ <br /> <br />RESULTS OF CALIBRATION <br /> <br />::>''-':i <br /> <br />To select parameters for model calibration, sensitivity analyses were <br />done on a number of sets of parameters. The most sensitive parameters then <br />were optimized using methods developed by Norris and Parker (1985) and using <br />the Gauss-Newton technique (Leaves ley and others, 1983, p. 49). <br /> <br />....N> <br />(,,:, :',,~ <br />,":::.t:i <br />""":'. <br />:'+..:,:' <br /> <br />'. -:;' ':~ <br /> <br />'".;"" <br />.~';>:';':. <br /> <br />~:;:< <br /> <br />;",':" <br />'. '.~, " <br /> <br />.. <br />;'>:'~:'!:I <br />~~~f::':,i <br /> <br />f~~::~'~ <br />'-'."..; <br /> <br />12 <br /> <br />~~~~ <br /> <br />'>:',' <br /> <br />~:'.:>':: <br /> <br />i',,,",;,' <br />