Trend in hydrological series and land use changes in a tropical basin at Northeast Brazil

Abstract

Flow is one of the hydrological variables of greatest interest due to its connection with water availability and its multiple uses. However, in recent years this resource has been threatened by intense land use and climate change, affecting patterns previously considered to be stationary. The goal of this study was to evaluate trends in changes of patterns of flow, precipitation, and land use in a basin located in the Brazilian Cerrado. 33 years of rainfall, fluviometric, and land use data were used, covering the period of 1985 to 2018 on an annual scale. Mann-Kendall and Sen Slope’s nonparametric test was applied to evaluate the trends in temporal series, as well as the Spearman Rho and Pettit, which were used to analyze the correlations between variables and detect the point of change in the series, respectively. The results show statistically significant trends in flow reduction over time. At the same time, a considerable reduction in natural areas occurred, with an increase of +750% in agricultural areas. The results also show that although a tendency to reduce precipitation was detected, its magnitude was not significant, with land use changes being the main factor for the negative changes in the flow of the Rio Grande tributary.

Long‐term trend analysis in annual, seasonal and monthly rainfall in East Northeast of Brazil and the influence of modes of climate variability

“…In the State of Alagoas, it was possible to detect patterns of changes in monthly rainfall, in which in the wettest months (from May to September) there were trends of reduction of monthly totals in the central region of the State, corresponding to clusters C2 and C3 (region with intermediate rainfall totals in the state-transition from the wettest region to the arid region). Rainfall in these regions is associated with distance from the coast and the deviation of trade winds and breeze circulations caused by the topography (Lyra et al, 2014(Lyra et al, , 2017 but rainfall patterns in recent years have been reported to be under the influence of land use and land use change (Correia Filho et al, 2019;da Silva et al, 2022;Santos et al, 2022).…”

“…Although some correlations indicate possible influences of PDO, SOI, ENSO and AMO at the breaking points, some trends did not show evidence of these influences. Changes in monthly rainfall may be partially due to natural climate variability, but may also be related to global warming and/or urbanization and changes in land use and occupation, as noted by Marengo et al (2020) for rainfall extremes in the Metropolitan Region of São Paulo (RMSP), Cecílio et al (2021) for the State of Espírito Santo and recently by Monteiro et al (2022) for Brazilian capitals and da Silva et al (2022) for NEB capitals. These studies highlighted the relationship between rainfall extremes and population growth in recent decades.…”

“…In the agroclimatic zoning for corn cultivation in Alagoas reported by Lima et al (2020), regions with greater fitness in the wettest months may have reduced apt area. Recently, some studies also point to a reduction in rainfall, due to the influence of changes in land use and occupation in the State (Santos et al, 2020) and with consequences in the water supply system and agricultural production (Correia Filho et al, 2019; da Silva et al, 2022; Souza et al, 2020a).…”