IMPACT OF CLIMATE CHANGE ON RESERVOIR RELIABILITY

Research and observations indicate that increases in atmospheric carbon dioxide (CO2) are raising global and regional temperatures, and producing changes in other climate variables that drive the terrestrial hydrological cycle, most notably precipitation and potential evaporation. This paper presents results of a study conducted to evaluate the possible impacts of climate change due to doubling of atmospheric carbon dioxide on the reliability of Mazowe reservoir in Zimbabwe. The reservoir supplies most of its water to citrus plantations. Thirty years (1961-1990) of hydrological data (reservoir inflows) and meteorological data were collected from the Zimbabwe National Water Authority (ZINWA) and Department of Meteorological Services, respectively. outputs from the Canadian Climate Centre (CCC) model for the 2CO2 temperature and rainfall scenarios were used in the study. The Penman model was used to estimate potential evapotranspiration, while reservoir catchment runoff was simulated using the Pitman lumped conceptual model. Research findings revealed that doubling of CO2 in 2050 would significantly increase mean monthly temperature by 3\ub0C, potential evapotranspiration (11.8%), rainfall (15%), runoff (23.5%) and annual reservoir yield (20.4%) at the 10% risk level. Based on the research findings, appropriate mitigation measures should be employed to minimise high rates of evaporation from the reservoir. on the other hand, the predicted high reservoir yield requires an increase in water use activities such as extension of irrigated area.La recherche et les observations indiquent que l\u2019accroissement du dioxyde de carbone atmosph\ue9rique (CO2) \ue9l\ue8ve les temp\ue9ratures mondiale et r\ue9gionale, et produit des changements dans d\u2019autres variables climatiques qui d\ue9terminent le cycle hydrologique de la terre, notamment la pr\ue9cipitation et l\u2019\ue9vaporation potentielle. Cet article pr\ue9sente les r\ue9sultats d\u2019une \ue9tude men\ue9e pour \ue9valuer les impacts possibles du changement climatique d\ufb \ue0 un doublement du dioxyde de carbone atmosph\ue9rique sur la fiabilit\ue9 du r\ue9servoir Mazowe au Zimbabwe. Le r\ue9servoir alimente en eau les plantations d\u2019agrumes. Trente ans (1961-1990) de donn\ue9es hydrologique (apports au r\ue9servoir) et m\ue9t\ue9orologique ont \ue9t\ue9 recueillies aupr\ue8s de l\u2019Autorit\ue9 Nationale de l\u2019Eau du Zimbabwe (ZINWA) et du D\ue9partement des services m\ue9t\ue9orologiques, respectivement. Les r\ue9sultats du mod\ue8le du Centre Climatologique Canadien (CCC) pour la temp\ue9rature 2CO2 et la pluviom\ue9trie ont \ue9t\ue9 utilis\ue9s dans l\u2019\ue9tude. Le mod\ue8le de Penman a \ue9t\ue9 utilis\ue9 pour estimer l\u2019\ue9vapotranspiration potentielle, alors que la r\ue9serve des eaux de ruissellement du bassin versant a \ue9t\ue9 simul\ue9e \ue0 l\u2019aide du mod\ue8le conceptuel de Pitman. Les r\ue9sultats de recherche ont r\ue9v\ue9l\ue9 que le doublement du CO2 en 2050 augmenterait de mani\ue8re significative la temp\ue9rature moyenne mensuelle de 3\ub0C,l\u2019\ue9vapotranspiration potentielle (11.8%), les pr\ue9cipitations (15%), le ruissellement (23.5%) et le rendement en r\ue9serve annuelle (20.4%) au niveau de risque de 10% .Se basant sur des r\ue9sultats de la recherche, des mesures appropri\ue9es de r\ue9duction du taux d\u2019\ue9vaporation \ue9lev\ue9 du r\ue9servoir devraient \ueatre prises. D\u2019autre part, le haut rendement de la r\ue9serve pr\ue9vu requiert une augmentation des activit\ue9s de consommation d\u2019eau telle que l\u2019extension de la zone irrigu\ue9e