Metodologia de avaliação da seca hidrológica sob a perspectiva da demanda hídrica

Abstract

The proper assessment of hydrologic drought to assist the monitoring of a possible water deficit may be crucial in the adoption of anti-drought attitudes, especially in the semiarid region, where this phenomenon is most frequent. However, traditional methodologies uses standardized drought indices, which do not express its severity in terms of the volume deficit and neither consider water demand as a component of its calculation. In order to overcome these disadvantages, this work presents evaluation methodology of hydrological drought, which determines the volume of water below its demand. It can be characterized in function of its duration, severity and magnitude, based on Threshold Level Method. For this purpose, the droughts that occurred between 1997 and 2015 were studied in two reservoirs of different capacities of the Piranhas-Açu River basin. Complementarily, it was used the method of valuation of hydrological drought developed by Araújo and Bronstert (2016) to compare the characteristics of drought events identified by different methods to the same reservoirs. For both methods, the results showed that the reservoir with higher storage capacity is more efficient and thus less susceptible to drought than the smaller. It was found that basic difference between the two approaches is the time analysis of drought events: while the Threshold Level Method is possible to study what occurred in the past to diagnose and make a planning of the use of water in future, the Araújo and Bronstert (2016) method enables the assessment of current conditions to anticipate the start of a hydrologic drought. In this perspective, it is suggested that the two methodologies presented in this paper can be used simultaneously by managers of water resources in order to enable a more comprehensive analysis of drought events in the basin.