Influence of multiple water uses on an cross-border watershed in South America

Knowing water behavior of water, such as flow and level in a watershed is extremely important to manage its multiple uses adequately. One of the models that has been highlighted by several studies and strategies to diagnose and understand hydrological processes and, consequently, define multiple water uses, is the Large Basin Model (MGB). The Mirim-São Gonçalo watershed (MSGW), which is a cross-border basin that stretches over the extreme south of Brazil and northeastern Uruguay, has significant environmental, economic, political and social importance to the population that lives there. This study aims at applying the distributed MGB to the MSGW to describe hydrodynamic processes and fluctuation resulting from water levels by considering input and output in the system, natural and anthropic ones, based on the Water Exploitation Index (WEI) and the Water Commitment Index (WCI). Results show that the adapted MGB enabled to simulate hydrological-hydrodynamic characteristics in the MSGW when information on winds were inserted. Results of the Brazilian part of the basin were better due to the distribution of input data. Regarding multiple uses, both the WCI and the WEI clearly show that the Uruguayan part of the basin is in a comfortable situation, in contrast with the Brazilian part, which needs special and criterial care since its situation is more critical.