Online Drought Indicators and Indices

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 has applied the SRSI methodology to several Asian river basins,

Reference: 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.

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