PROJECT SUMMARY

The primary objective this project was to generate up to 1000 years of weekly stream flows for the Bow River at Calgary and North Saskatchewan River at Edmonton. This unique data set enabled a secondary objective: an evaluation of the reliability of current water supply and management systems given the range of hydro-climatic variability and extremes in this unique paleo and projected hydrology. To achieve the first objective, we combined the methodologies of paleohydrology, the study of water over centuries and millennia, and stochastic hydrology, the use of statistical methods to generate randomized hydrological times series that closely represent natural hydrologic processes. Stochastic hydrology provides hydrologic variability that is statistically likely to occur, but also more challenging to manage than historic flows, either in terms of the magnitude of individual events or their duration. One of the main shortcomings of stochastic hydrology is that the generated output series preserve the annual flow statistics of relatively short historic records. Using paleoclimatic data to generate 1000 years of weekly flow estimates introduces hydrologic variability and sequences of wet and dry years that are not evident in the short historic flow record. From centuries of weekly river flows we can derive a) long-term past probabilities of low flows of specific severity and duration, b) evaluate the reliability of gauge records as the basis for nearly all decisions about water allocation, diversion and storage, and c) transfer of this new information on hydrologic variability to water managers for their assessment and use as input into water management models.