Intrusão salina no estuário do Rio Incomati

Abstract

Saline intrusion through the Incomati River estuary has been frequent in recent years, with greater incidence in the dry season. This phenomenon is due to the reduction of flows in the river, which is a consequence of the development that the Republic of South Africa (RSA) has undergone, which contributes to the river flows being dependent on human actions in that country, that is, , river water is used in that country's industries. These low levels of flow have been creating great damage on the Mozambican side, affecting above all agricultural development in the lower Incomati. This work is a study on the interaction of tides with river currents, variation in salinity, density and water temperature. It seeks to show that the tidal range, even in the middle estuary, is sufficient to create a current that opposes the river flow resulting in saline intrusion into the estuary. It is also shown that intrusion is an inverse function of river flow. In this study, the flow of 254m3s‘' was determined as being the minimum necessary for the salt water not to reach the fields located on the right bank of the lower Incomati, in Marracuene, about 20 km from the mouth of the river. This flow was determined using the diffusion equation. This measure is extremely important if we take into account that it can allow us to rationally manage the flows at the local level, in order to minimize the saline intrusion into the river and thus allow agricultural development in the lower Incomati. Based on the results of the observations and the model, it was possible to conclude that the Incomati River is quite prone to saline intrusion, a fact that is associated with the low flows, which have been verified lately, and with the tidal height that reaches 1.0 meters the middle estuary. It was also possible to determine that the probability of intrusion occurrence is quite high even in the rainy season. (TRADUÇÃO NOSSA)