Stochastic analysis of storm water quality control detention ponds

Storm water detention ponds are recognized as an effective type of treatment facility for urban storm water management purposes. This paper presents methodologies for the development of an analytical stochastic model describing the hydrologic operation of storm water quality control detention ponds with outflows controlled by orifices. The concept of effective storage capacity is proposed to properly represent a pond's storage in its stochastic water balance equation. The accuracy of the analytical stochastic model (ASM) is verified for many different hypothetical design cases. It is shown that the ASM for detention pond systems can provide accurate results for almost all possible design conditions. Implemented easily into a spreadsheet, the ASM provides an easy-to-use and computationally-efficient tool for analyzing the hydrologic performance of detention pond systems. The ASM can be used separately as a planning or design tool or together with continuous simulation models to help verify simulation results or reduce the number of simulation runs.