Global Storage-Reliability-Yield Relationships for Water Supply Reservoirs

Storage-Reliability-Yield (SRY) relationships are used to determine the reservoir storage capacity for delivery of a specified yield with a given reliability, or to compute the yield and/or reliability of an existing reservoir system. Several studies have developed generalized SRY relations using synthetic inflows arising from a variety of theoretical streamflow models. Fewer studies have used actual streamflow datasets to develop generalized SRY relationships and most of those studies were for small geographic regions. This study uses a global dataset of monthly streamflows combined with robust regression methods to develop improved generalized SRY models suitable for use anywhere in the world. Comparisons are provided between the models developed here and other studies documenting a number of innovations over previous relationships. In cross validation experiments our global reservoir yield model exhibited extremely high goodness-of-fit with values of Nash Sutcliffe Efficiency and adjusted R-2 values both always in excess of 0.99 and negligible bias. The resulting SRY model should prove useful in screening studies which seek to evaluate the benefits of constructing reservoirs for surface water supply.