WSP07957 - Laserfiche WebLink

Home Browse Search

.-' . . ,I'") In L.'J c) ~'-! CHAPTER II GRAND VALLEY RIVER BUDGET Using the the National Weather Service's Normal Annual Precipitation for Colorado Map and the USGS daily data for West Salt Creek, the ratio of the mean annual volume of runoff to the mean annual volume of precipitation was 0.0023. When the ground water flow in the West Salt alluvium at the gage is added, the ratio becomes 0.0025. Since the magnitude of the ungaged inflows appeared to be very small, and therefore insignificant to the river budgeting process, it was decided to assume a constant runoff per are,!! factor for all ungaged areas, based on West Salt's flow and drainage area. It was then attempted to extend West Salt's record by correlating to another station. In order to preserve West Salt's statistical variance, it would be necessary to transform both stations' records before correlating such that the transformed values would be normally distributed. Unfortunately, due to the large percentage of zero flo.. months, no transformation was found to make West Salt's flow anywhere r~ar normally distributed. 'Abandoning transformations, it was then attempted to simply correlate West Salt's flow to each of the surrounding USGS flow stations on both a monthly and annual basis, with very poor results. Then a correlation was attempted using West Salt's annual flow against the precipitation during various portions of the year. The sum of December, January, and February precipitation provided the best regression (coefficient of determination R2 = 0.28) and was used to extend West Salt's annual flow record. The monthly flows were estimated by assuming that each year's IIIOnthly dii3tribution of flow was the same as the average for the 6-year record. Beci!!use of the scarcity of data, the surface water quality for the generated flows was II-4