Variabilidade climática natural e sua relação com os recursos hídricos superficiais da bacia hidrográfica do Alto Rio das Velhas

Abstract

One of the most important issues of the 21st century is the integrated management of available water. The management instruments of the Brazilian National Water Resources Policy, particularly the granting of the right to use, seek to ensure that there will be sufficient water both in quality and quantity for all users, having the watershed as the basic planning unit. The management of water resources is built on the premise of satisfactory water availability, in which society can have its demands fulfilled. The study of the climate natural variability, including its extremes, is justified by the need to adapt to scenarios where extreme events may be more frequent and the loss of stationarity of the series can impose important changes in sectors such as power generation, irrigation and water supply, among others. This work sought to understand whether (and how) natural climate variations may interfere with the surface water availability of the upper Rio das Velhas watershed, located in the central region of the State of Minas Gerais (Brazil). It aimed to identify changes in rainfall and flow data on the watershed that are compatible with the occurrence of the following climate variability indices: El Niño–Southern Oscillation (SOI/ONI), Pacific Decadal Oscillation (PDO) and Tropical Atlantic SST Dipole (TNA/TSA). For that, the following specific objectives were defined: (i) to identify the existence of trends in the rainfall and flow data available for the basin area; (ii) to analyze the series of hydrological data, correlating them with the periods in which the climatic variability indices occurred; (iii) define the existence of scenarios in which anomalies in the hydrological series occur from the manifestation of the climatological phenomena. Results have shown that the interactions between the analyzed phenomena (IOS, INO, ODP and TSAI / TNAI) in the study area are weak or inconspicuous. For the ODP and TSAI / TNAI indices, there was a high dispersion of data, representing a low correlation index. In the case of the La Niña phenomenon, it was possible to identify an increasing trend in precipitation during the rainy months in scenarios without temporal displacement or with a 12-month temporal displacement (after the event). For the El Niño phenomenon, it was possible to identify a tendency to reduce precipitation in the dry months. The conclusion is that because these are macro-global phenomena that occur over time, it is difficult to identify correlations. The time of response in the Basin to global phenomena is another limitation that must be considered in future studies.