ASSESSMENT OF THE WATER DEFICIT IN THE HYDROGRAPHIC REGION OF THE STATE OF ESPÍRITO SANTO

Name: Julielza Betzel Baldotto
Type: MSc dissertation
Publication date: 16/11/2022
Advisor:

Namesort descending Role
Diogo Costa Buarque Advisor *

Examining board:

Namesort descending Role
Antonio Sérgio Ferreira Mendonça Internal Examiner *
Diogo Costa Buarque Advisor *
RODRIGO CAUDURO DIAS DE PAIVA External Examiner *

Summary: 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. Dry events have been treated by means of 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. To this end, gravimetric analyzes are being used
to record the movement of water across the globe and on a time scale. The GRACE (Gravity Recovery
and Climate Experiment) mission is a pair of satellites that have sensors capable of capturing this type
of information and by processing these signals, diagnosing values that represent the water equivalent
of a region, that is, what is stored in the locality in a period. In this study, the water storage values
processed by the CSR (Center for Space Research), at the University of Texas, were converted into
average monthly water storage anomaly values, over each watershed that makes up the region of the
State of Espírito Santo, to represent the spatiotemporal water deficits that occurred in the period from
2002 to 2020 and characterize them as dry events. In addition, the MGB model was evaluated as a tool
to simulate water storage values through comparison with GRACE values, in order to project average
monthly water storage anomaly values, investigating water shortages from 1950 to 2019. To
characterize the water deficits, some statistical measures were applied on the average monthly water
storage anomaly values, determining the duration, trend, frequency, magnitude, severity and recovery
time of these dry periods. For the simulations with the model, the MGB was calibrated with
fluviometric data and, from its outputs, the monthly average anomaly values of water storage were
calculated, to be compared to the GRACE values by efficiency coefficients. With this, it was also
possible to simulate water deficit values for the past period. As a result, the GRACE mission diagnosed
a trend of more intense water deficit in the northwest direction of the evaluated region and a
frequency of long-term dry events, with emphasis on three of them: the first from 2002 to 2004, the
second, of greater severity and magnitude, which occurred from 2014 to 2017, which does not recover
before the third event, from 2018 to 2020. The simulation of water storage with the MGB proved
capable of reproducing values of water deficits captured by the satellites. The projection of average
monthly anomaly values of water storage with the MGB showed that the hydrological region in which
Espírito Santo is located suffered from droughts in most of the 50`s, in some years of the 60`s and 70`s,
in the second half of the 1980s, throughout the 1990s, in some years of the 2000s and with the last
prolonged drought, from 2014 to 2019. Of these, most are cited in the literature. In this way, GRACE
signals captured the main dry events that occurred in Espírito Santo. On the other hand, the MGB
proved to be an effective tool to reproduce the water storage values, mainly in larger basins, such as
the Doce river basins.

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