Avaliação do déficit hídrico na região hidrográfica do Estado do Espírito Santo

Abstract

The study of water storage deficits over a region, characterizing its variations in space and time, determining what would be considered a dry event, reveals possible behaviors of what can be expected as a water crisis or warning signs for it. The State of Espírito Santo went through a long period, starting in 2014, in crisis due to the lack of water, reaching the prioritization of the resource for human consumption. These dry events have been studied using indices that often consider the lack of normal rainfall, only from the perspective of meteorology or only focused on the agricultural area. However, some tools are able to record variations in water masses in all their verticality, thus achieving the determination of the periods in which changes in water storage occurred in a broader way, over the entire ecosystem. For this purpose, gravimetric analyzes are being used to record the movement of water across the globe and on a temporal scale. The GRACE mission (Gravity Recovery and Climate Experiment) is a pair of satellites that have sensors capable of capturing this type of information and, by processing these signals, diagnose values that represent the equivalent of water in a region, that is, what is stored in the locality in a period. In this study, average monthly water storage anomaly values for each river basin that make up the region of the State of Espírito Santo are used to characterize dry events in the period from 2002 to 2020. In addition, the MGB model is evaluated as a tool capable of simulating water storage values compared to GRACE and by projecting average monthly water storage anomaly values characterizing dry events from 1950 to 2019. As a result, the GRACE mission diagnosed a trend of water deficit of greater intensity in the northwest direction of the evaluated region and the recurrence of dry events of long duration. The most relevant dry events diagnosed by satellite data include: the period from 2002 to 2004; the period from 2014 to 2017, of greater severity and magnitude; and, the period from 2018 to 2020, occurring before the previous event recovers. The simulation of water storage with the MGB proved capable of reproducing water deficit values, when it reproduces the years 2003, 2007-2008 and the decade of the 2010s with dry events, with efficiency and compatibility of results with the values produced by the GRACE satellites, mainly for larger basins. In the projection of average monthly water storage anomaly values with the MGB for the period 1950-2019, the simulation showed that the hydrological region in which Espírito Santo is located suffered from relevant dry events in most of the 50s, in some years of the 60s and 70s, in the second half of the 80s, throughout the 90s, in some years of the 2000s and with the last prolonged drought, from 2014 to 2019. Of these, a large part is cited in literature. Which reinforces its possible occurrences. Therefore, it can be inferred that the Espírito Santo region has already experienced droughts as severe as those of 2014. And that, based on these results, the work demonstrated that the GRACE signals captured the main dry events that occurred in Espírito Santo. The MGB, on the other hand, proved to be an effective tool to reproduce water storage values.