Estimativa do caudal ambiental para o estuário de rio Incomáti

Abstract

In recent decades, population growth has led to an exponential increase in water demand. In the midst of the dilemma between the need to preserve aquatic and riparian ecosystems, and the demand for water abstraction from rivers for various uses, the problem of reducing river flows arises, significantly altering the ecological conditions of riparian ecosystems, particularly those close to the coast due to saline intrusion. In this context, this work aims to estimate environmental flows for the Incomati River estuary by considering ecosystem modeling. Ecosystem modeling requires biological and physical-chemical information, as well as social and economic information about the site. To this end, we compiled (1) biological information, which includes phytoplankton, zooplankton, macrofauna and birds; (2) information on ecosystem services, (3) water quality and (4) hydrological information available for the Incomati River estuary. Based on the available information and consultation with stakeholders, the conclusion was reached that in order to preserve ecological conditions and the availability of ecosystem services, saltwater intrusion should be contained within 30 km of the mouth of the estuary.Based on hydrological and water quality modeling, particularly of saline intrusion, the environmental flow to contain saline intrusion at 30 km from the mouth of the estuary was estimated at 80 m3/s. However, the flow estimated by the modeling cannot be guaranteed throughout the year, according to ARA-Sul, due to hydraulic infrastructure limitations. As the proposed flow was estimated considering extreme conditions, high equinox tides, we can consider maintaining a flow of 80 m3/s for the months of March and September, during equinox tides, and a flow of 40 m3/s for the remaining months. If saltwater intrusion exceeds 30 km, management measures should be adopted to preserve the agricultural areas in the Hobjana area. The environmental flow estimated in this study could be improved by including sediment transport and field measurements. (TRADUÇAO NOSSA)