Abstract:
This study investigates the concurrent impact of reservoir storage and extreme rainfall on the devastating Kerala foods 2018
using Copulas. First, the efect of storage of four major reservoirs Idukki, Idamalayar, Kakki and Kallada is investigated by
developing storage curves. It is noticed that in the four reservoirs, the storage level was above the decadal mean storage in
most of the days of July–August period of 2018. An analysis on the storage levels of the four reservoirs showed that the water
level crossed the spillway crest level of the respective reservoirs by July 26, 2018 and the controlled release might have helped
in alleviating the food disasters. In the Copula-based modeling, frst, the marginal distribution of monthly storage and rainfall
of the four reservoirs are developed and it was found that the generalized Pareto (GP) distribution was ftting best for all the
storage data. The exponential ft was found to be the best for rainfall of all reservoirs except that of Kakki. Subsequently, the
joint probability of reservoir storage and rainfall is investigated using three popular Copulas of Archimedean family namely
Gumbel–Hougaard (GH), Clayton and Frank and the best Copula is identifed for each case. The return period curves are
developed for both joint and conditional cases using the best ftted Copula. The sensitivity analysis of joint return period
showed that the rainfall of Kakki and Idukki at 2018 was extreme and the efect of rainfall is dominant in these reservoirs.
