Avaliação do potencial de uso da água subterrânea para expansão da irrigação na bacia do buriti vermelho

In Brazil, the increasing middle class has raised food demand substantially. The Brazilian Savannah (Cerrados) is one of the rare places where agriculture can expand and address this new demand without jeopardizing the environment. Cerrados has a strictly divided dry and wet season. The dry season lasts from May to September. This long period contributes to various problems such as water shortages, conflicts and insecure food production. Without irrigation, only two crops can be grown per year in this region. Production suffers with a recurrent drought. Because agricultural production is uncertain, irrigation has an important role in this context, but its expansion is limited by water availability. Water conflicts have already occurred in some watersheds, which may jeopardize agriculture and decrease the livelihood of rural communities. In general, water for irrigation is limited to surface water. Therefore, it is important to investigate alternative sources of water, like groundwater. The purpose of this study is to assess the groundwater potential for expanding the irrigated area in a small-scale catchment (Buriti Vermelho, DF, Brazil). The current water demand was investigated and simulated by an Irrigation Strategies Simulation Model (MSEI). A daily water balance was computed, which quantified catchment storage over time. In addition, groundwater behavior and availability were investigated by recession curve analysis. The irrigated area was changed using two scenarios that showed different effects in both catchment surface water balance and groundwater levels. A decline in groundwater levels is seen in all scenarios one year after the beginning of extra extraction. With time, water levels may decline beyond the natural recovery capacity, which will certainly penalize poorer farmers and result in areas being taken out of agricultural production.