To represent the both qualitative and quantitative physical factors that impact water availability over time, three indices were created for the basins. Given constraints in time and resources, best approximate values of the physical water situation, not actual volumes, were developed. These proxy values can be used as relative indicators of trends in water quality and quantity.
Drought Index- A drought index was created to represent the variation in water availability for each basin during the water year. It aggregates several variables that impact the amount of water physically available in the system before human use. The values for each basin are created independently of each other, thus the information does not show that Oregon's eastern basins are drier than the western, but shows how dry a basin is that year compared to the basin's average.
Consumptive Use Index- This is a measure of how much water in a basin is dedicated to consumptive uses relative to the amount available in the stream. In other words, it approximates an instream flow amount and an amount diverted for various uses. Oregon regulations require that a river system total diversions cannot be higher than the 80% exceedance flow (the total flow that is exceeded 80% of the time).
Water Quality Index- This water quality index represents the overall water quality in winter and summer for each administrative basin by incorporating 8 different variables.
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Contact Kristel Fesler via email: feslerk at geo.oregonstate.edu
Updated October 2005