Standardized Reservoir Supply Index (SRSI)
Index name: Standardized Reservoir Supply Index (SRSI).
Ease of use: Yellow.
Origins: Developed by Gusyev et al. in Japan as a systematic way to analyse reservoir data in drought conditions.
Characteristics: Similar to SPI in that monthly data are used to compute a probability distribution function of reservoir storage data, to provide information on water supply for a region or basin within a range of -3 (extremely dry) to +3 (extremely wet).
Input parameters: Monthly reservoir inflows and average reservoir storage volumes.
Applications: Takes into account the total inflow and storage associated with any particular reservoir system, and provides information for municipal water supply managers and local irrigation providers.
Strengths: Easy to compute, as it mimics SPI calculations using a standard gamma distribution of the probability distribution function.
Weaknesses: Does not take into account changes due to management of the reservoir and losses due to evaporation.
Resource: The International Centre for Water Hazard and Risk Management (ICHARM) has applied the SRSI methodology to several Asian river basins.
Gusyev, M.A., A. Hasegawa, J. Magome, D. Kuribayashi, H. Sawano and S. Lee, 2015: Drought Assessment in the Pampanga River Basin, the Philippines. Part 1: A Role of Dam Infrastructure in Historical Droughts. Proceedings of the 21st International Congress on Modelling and Simulation (MODSIM 2015), Broadbeach, Queensland, Australia. DOI: 10.13140/RG.2.1.4931.4321.
Shiau, J.T., 2003: Water release policy effects on the shortage characteristics for the Shihmen reservoir system during droughts. Water Resources Management, 17: 463–480. DOI: 10.1023/B:WARM.0000004958.93250.8a. (For more information on this paper, please contact the IDMP HelpDesk).