Efeito de secas prolongadas nos recursos hídricos de uma região semiárida: uma análise comparativa para o Ceará

Abstract

This paper presents a simplified methodology to evaluate the effects of the extended drought that occurred between 2012 and 2016 in a semi-arid region in Ceara state, based on data provided by the Water Resources Management Company and the Meteorology and Water Resources Ceara Foundation. The study evaluated the impacts considering three main points: the rainfall regime during rainy season; the regularization reservoirs; the reduction of water supply for irrigation and popular consumption. A comparison was also made between the equivalent reservoir of Northeast states in the period, based on data presented by National Water Agency, as well as a comparison between the evolution of the accumulation percentage of Castanhão Reservoir- CE and Cantareira System - SP, which also suffered the effects of a water crisis in the period 2014-2015. The results showed that rainfall during rainy season was always below the historical average in the period, with highlight for 2012, with a -50.7% difference. The years of 2012, 2013 and 2016 are among the ten worst in terms of rainfall in the state. The average contribution of the reservoirs in the period was 0.91 billion m³/year, with a reduction of 78.25% in the accumulated volumes in these reservoirs between 2012 and 2016. The irrigated perimeters showed an 84.4% drop in the offered flow, while 74.4% of the cities decreed a state of emergency due to drought at the end of 2016. For the northeast, Ceara, Paraiba, Pernambuco and Rio Grande do Norte were the states where the reservoirs suffered the most from the extended drought, while Bahia and Piaui were less affected. In the comparison between Castanhao - CE x Cantareira - SP, even with the causes and effects of the droughts being different, the two reservoirs reached levels below the operational minimum, even using the dead volume for supply. Combining the results of the present study with previous works on drought, it has been shown that climate changes have not created more severe meteorological droughts. Even so, situations of extreme droughts and prolonged droughts continue to have a worrying effect on the populations. Finally, the analysis can serve as a preliminary tool to evaluate the impacts of extended droughts in the semi-arid, enabling more efficient actions in the management of water resources.