<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 />
|