Statistical Parameters Used for Assessing Hydrologic Regime

The importance of hydrologic flow regimes and flow metrics is well acknowledged by hydrologists, ecologists, and water resource managers. Human interventions, such as water reservoir, water supply, hydropower generation, flood control, recreation, and navigation, modify the flow regimes and thereby affect their ecosystems. Stream flow characteristics such as magnitude, frequency, duration, timing, and rate of change of flow events are significantly important for developing flow regime and stream regionalization. Each stream possesses their own flow characteristics that support a particular biological community. The interannual variability of flow acts as a dynamic force affecting stream ecosystem functions. Urbanization affects the flow regime by changing their flow frequency, volume, peak, base flow, erosion and sedimentation, and water quality. Urbanization induced changes in flow regime include increased flow frequency, increased peak flow and total flow, and decreased base flow. Runoff from impervious areas generally flows quickly and carries diverse sources of pollutants. Therefore, proper understanding and quantification of flow regime is critically important. A number of statistical flow parameters are being used for classification of flow regimes. In this chapter, stochastic flow parameters used in flow regime classification and in ecohydrological studies are delineated.