Utility of Climate Information Based Reservoir Inflow Forecasts in Annual Water Allocation – Ceara Case Study

A dynamic water allocation framework for a multipurpose, single reservoir is formulated to utilize climate information based reservoir inflow forecasts to quantify the reliability of use for the given demand. Based on the semi-parametric approach of De Souza and Lall [2003], 12 months lead retrospective reservoir inflow forecasts were developed for the period July 1990June 2000 for the Oros reservoir utilizing the climatic conditions available up to June of that year. Based on the actual annual demand to be supplied by the Oros reservoir for the JMH system, the utility of climate forecasts for multipurpose water allocation is assessed utilizing the adaptive forecasts developed for the period 1990-2000. Since Oros reservoir is a multi-year storage reservoir, the initial storage available in July of every year was adequate enough to supply water for all the uses even under zero inflow assumption thereby reducing the utility of climate forecasts during normal inflow years. On the other hand, climate information based reservoir inflow forecasts is more beneficial in meeting the annual demands of the Oros system for different uses during above-normal and below-normal inflow years than during normal inflow years. Analysis of the results suggests that the utility of climate information based reservoir inflow forecasts is more pronounced for systems with high demand to storage ratio.