Morphosedimentary dynamics of the Salado River, hydroclimatic variability, and alterations caused by the dam at General Belgrano, Buenos Aires

Abstract

The flood risk along the banks of the Salado River represents a serious socio-environmental issue. Despite various measures being taken to mitigate this problem, the consequences during drought-typical phenomena of the Pampean region—have not been adequately addressed. This study examines the geomorphological and environmental changes that occurred in a stretch of the Salado River following the construction of two dams in the General Belgrano area. Two river sections were compared: one stagnant and the other natural, from which sediment and water samples were collected. In the stagnant section, a higher sedimentation rate was observed compared to the natural section, with the presence of muddy sediments (15 % sand), high organic matter content (11.42 % by weight), low compaction, and dark colors. Additionally, an anoxic environment was generated, with an ORP of 27 mV (reductive), high organic degradation, and a high degree of eutrophication. Alkaline pH values (9.28), a more than double increase in salinity (49.08 µS/cm), and higher temperature (32.84 °C) were recorded compared to the natural section. These negative impacts led to aquatic fauna mortality, significantly affecting local tourism. Core samples revealed the sedimentary and environmental changes in both river sections after the construction of the dams, reflected in alterations in sediment texture, color, and compaction. It is recommended to regulate water levels before potential droughts and to avoid discharging domestic effluents to prevent eutrophication of the system.