REGIONAL VARIATIONS IN FLOW-DURATION CURVES FOR RIVERS IN BRITISH-COLUMBIA, CANADA

The estimation of flow quantiles and the regionalization of hydrologic characteristics are two major foci of current hydrologic research. A flow-duration curve represents the annual flow-frequency characteristics of rivers by depicting the cumulative frequencies for average ranked flows in a river. Generally the process requires the empirical estimation of the mean flow at each of 365 ranks. A model requiring only five parameters is developed by combining the principles of order statistics and traditional flow-frequency analyses and is applied to flow-duration curves for rivers in the province of British Columbia, Canada. Results from the model may be interpreted both statistically and physically and allow the identification of hydrologically similar regions. Streamflows in British Columbia are generated from a number of distinct physical processes operating in highly diverse environments. The mixture of the streamflow-generating processes requires that the statistical model be capable of encompassing the different flow-frequency regimes. Identification of hydrologic regions also depends on the inclusion of these generating processes. The model presented incorporates the physical generating processes of streamflow in both the statistical representation of flow-duration curves and their interpretation. Similarly, the spatial model presents hydrologic regions that correspond to the known physical environment.