Assessment of aquifer recharge and groundwater availability in a semiarid region of Brazil in the context of an interbasin water transfer scheme

Abstract

Particularly in arid and semiarid areas, more and more populations rely almost entirely on imported water. However, the extent to which intentional discharge into transiting river systems and unintentional leakage may be augmenting water resources for communities along and down gradient of the water transfer scheme has not previously been subject to research. The objective of this study was to assess both the potential of a large-scale water transfer (WT) scheme to increase groundwater availability by channel transmission losses in a large dryland aquifer system (2,166 km²) in Brazil, and the capability of the receiving streams to transport water downstream under a prolonged drought. An integrated surface-water/groundwater model was developed to improve the estimation of the groundwater resources, considering the spatio-temporal variability of infiltrated rainfall for aquifer recharge. Aquifer recharge from the WT scheme was simulated under prolonged drought conditions, applying an uncertainty analysis of the most influential fluxes and parameters. The annual recharge (66 mm/year) was approximately twice the amount of water abstracted (1990–2016); however, the annual recharge dropped to 13.9 mm/year from 2012 to 2016, a drought period. Under similar drought conditions, the additional recharge (6.89 × 106 m³/year) from the WT scheme did not compensate for the decrease in groundwater head in areas that do not surround the receiving streams. Actually, the additional recharge is counteracted by a decrease of 25% of natural groundwater recharge or an increase of 50% in pumping rate; therefore, WT transmission losses alone would not solve the issue of the unsustainable management of groundwater resources.

Understanding hydrological connectivity: an empirical study of river-aquifer interaction across Brazil

“…The results suggest that three of the four explanatory variables investigated show a robust correlation (p-value < 0.001) with the fraction of well water levels lying below the nearby stream surface (Figure 13). The strong correlation found for P/PET (ρ = −0.34 to -0.47; Figure 13b) supports the argument that dry regions are more likely to have losing rivers (Schaller & Fan, 2009;Jasechko et al, 2021;Costa et al, 2023), as these regions favor surface runoff, which quickly reaches the streams. The latter lose it to aquifers due to the deep water table (Fan, 2019;Bierkens & Wada, 2019).…”

“…Given the importance of these interactions for determining channel transmission losses for water resource management in the region. Costa et al (2012a) were among the first to develop a process-oriented channel transmission losses model. Their model was designed to account for surface-subsurface water fluxes in data-scarce dryland environments, and its potential was confirmed in the Middle Jaguaribe River Basin, Ceará.…”

“…Recent studies by Toné et al (2023) developed a conceptual model of the river-aquifer interaction for this basin, indicating the spatial and temporal dynamics of these interactions according to the seasons. Furthermore, Costa et al (2023) investigated the potential influence of the São Francisco River interbasin water transfer scheme on groundwater resources in the state of Ceará using an integrated surface-water/groundwater modeling approach. They found that this water transfer scheme could decrease the stress on groundwater resources in the Medium Aquifer system; however, it would have a limited effect on the areas surrounding the receiving streams.…”

“…River-aquifer interactions play a crucial role in the fields of ecohydrology and biogeochemistry, with significant implications for the management of water resources (Lewandowski et al, 2019;Bierkens et al, 2021). These interactions are essential for addressing various engineering challenges, such as determining groundwater recharge rates (Yuan et al, 2020;Wendland et al, 2022;Costa et al, 2023), understanding strategies to prevent contamination and restore ecosystems (Schneider et al, 2011;Lasagna et al,2016;Herzog et al, 2023), assessing the vulnerability of streams to climatic variations (Datry et al, 2014;Malish et al, 2023;Silverthorn et al, 2023), and mediating water-energy fluxes and partitioning (Maxwell & Condon, 2016;Miguez-Macho & Fan, 2021;Hellwig et al, 2022). Therefore, a thorough understanding of the mechanisms that govern the spatial patterns and temporal dynamics of river-aquifer interactions is crucial for enhancing our comprehension of hydrological processes (Schaller & Fan, 2009;Fan, 2019;Ballarin et al, 2022).…”