Evolution of Drought Mitigation and Water Security Through 100 Years of Reservoir Expansion in Semi‐Arid Brazil

• Published in: Water resources research 2024-09, Vol.60 (9), p.n/a
• Main Authors: Meira Neto, Antônio Alves, Medeiros, Pedro, Araújo, José Carlos, Pereira, Bruno, Sivapalan, Murugesu
• Format: Article
• Language: English
• Subjects: Aridity; Catastrophic events; coevolution; Complex systems; Construction; Dam construction; Drought; droughts; Environmental impact; Evaporation; Evolution; Hydrologic models; Hydrology; Local population; Mitigation; Outlets; Population studies; Provisioning; reservoir; Reservoir construction; Reservoir storage; Reservoirs; Security; semi‐arid; Storage capacity; Storage conditions; Stream discharge; Stream flow; Sustainability management; Water; Water demand; Water management; Water resources; Water scarcity; Water security; Water storage
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2023WR036411

Brazil's Northeast region (BRN), especially the state of Ceará (CE), has dealt historically with severe drought events since the late 1800s, which commonly led to catastrophic impacts of mass migration and deaths of thousands of people. Throughout the last century, the “Droughts Polygon” region experienced an intense infrastructural development, with the expansion of a dense network of reservoirs. This paper presents a parsimonious hydrologic modeling approach to investigate the 100‐year (1920–2020) evolution of the hydrology of the 24,500 km2 Upper Jaguaribe Basin, throughout the development of a dense reservoir network. We aimed at reproducing the hydrology at the basin scale and analyzed the outcomes of reservoir expansion in terms of water fluxes and water security. Our model's structure captured the growth in reservoir count and storage capacity, which was then confronted with an evolving water demand, allowing us to estimate how water security (i.e., proportion of demand being met) varied over the 100‐year period. Significant streamflow reduction at the basin's outlet and increase in evaporation losses, associated with a decrease in streamflow at varying exceedance frequencies were observed at the end of the study period. While reservoir expansion allowed for the transition from complete vulnerability to meteorological droughts to increased levels of water security, drought impacts had, in the meantime, disproportionally intensified, especially in reservoirs of medium to small capacities. Smaller reservoirs are suggested to have played the role of distributing water resources throughout the region, while larger reservoirs were more efficient as tools to promote water security. Plain Language Summary Brazil's Northeast region is known to suffer from severe droughts since colonial times. The state of Ceará is perhaps the best representation of how hydraulic interventions were used in the last century to mitigate water scarcity in Brazil's semi‐arid. Recently, the debate on how widespread construction of reservoirs can lead to unintended (negative) consequences in terms of water provisioning has been the brought to the attention of the scientific community. Studies to quantitatively characterize such phenomena are thus necessary to create basic understanding on how humans interact with water systems, with the potential of promoting more sustainable water management practices. In this study, we investigate a large region in the state of Ceará that experi