DINÂMICA DA DISPONIBILIDADE HÍDRICA E USO/OCUPAÇÃO DA TERRA EM BACIAS HIDROGRÁFICAS NO SUDOESTE GOIANO

Abstract

The growing demand for water resources due to population growth with consequent land use and occupation by humans as well as the inexistence/insufficiency of hydrological data in unmonitored regions cause the need to carry out studies on water availability and on land use and occupation of the hydrographic basin, aiming to serve the population and mitigate conflicts related to the problem. Thus, this paper aims to evaluate water availability with possible influencing factors in hydrographic basins around the municipality of Rio Verde, Goiás State, Brazil, for forty years. The methodology primarily involves the circumscription of the study area covering the Rio Verdinho, Rio Verdão, and Rio Monte Alegre hydrographic basins. Satellite images were acquired from the USGS Earth Explorer database and processed in QGIS by the TauDEM extension. Then, pluviometric and fluviometric data registered in Hidroweb-ANA were collected from the chosen monitoring points to get the historical series of flow and precipitation. Then, supervised classification was carried out regarding land use and occupation in QGIS through the Dzetsaka Classification Tool extension, providing the percentage of native vegetation, irrigated agriculture, and urbanized areas in each hydrographic basin. Finally, a statistical technique of multiple linear regression was applied to have equations relating the “land use and occupation” and the “water availability” of the evaluated hydrographic basins. Results indicated that the flow Q95% had a decay trend over the forty years for all the hydrographic basins studied. On the other hand, the annual accumulated precipitation has kept a steady trend line for the Rio Verdinho and Rio Verdão hydrographic basins and an upward trend for the Rio Monte Alegre hydrographic basin, despite fluctuating during the period. There was also an increase in land use in all hydrographic basins for agricultural purposes, either irrigated or not irrigated. Thus, it is concluded that the decline in flow Q95% with considerable constancy or increasing precipitation is probably related to land use and occupation, mainly due to increased irrigation. These data must be considered for the prediction of scenarios and efficient management of the region's water resources.