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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2008-5070

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Sensitivity Analysis

A series of simulations were conducted to determine the relative effect of selected input variables and model parameters on simulated water temperatures. One input variable or model parameter in the calibrated Roza–Prosser Reach model was changed for each simulation by a percentage, although all other variables and parameters were held constant. As shown in table 10, the resulting percentage of change in daily mean water temperature for the simulation period was measured and recorded for one Hydromet site (Grandview) and two TidbiT sites maintained by Bureau of Reclamation. The period for the sensitivity simulations was from April 1 through October 31, 2005, and used weather data from the AgriMet weather station (Harrah). Simulations for July were run to determine seasonal patterns of sensitivity.

Daily maximum and mean water temperatures for the Roza–Prosser Reach model were most sensitive to daily mean air temperature. Daily maximum water temperatures were more sensitive than daily mean water temperatures to solar radiation, and both simulated daily maximum and daily mean water temperatures were more sensitive to solar radiation than to relative humidity.

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