Research Outputs
Effects on fluvial geomorphology and vegetation cover following hydroelectric power plant operation: A case study in the Maule river (Chile)
The installation of hydroelectric plants has generated multiple environmental impacts on the world’s river systems. In central Chile, the impacts of hydroelectric reservoir operation have been documented in ecological and hydrologic regime terms. This investigation assesses the changes in channel morphology, vegetation distribution, and flows in the middle section of the Maule River during the period following the start-up of a hydroelectric plant. Changes in fluvial morphology (active area) and land cover are quantified using LANDSAT images, contrasted with a vegetation sampling and flow analysis. The results show a 12% decrease in active areas of the river, indicating a loss of geomorphological diversity. Within the active channel, there was a gradual increase in plant-covered surface area, which reached 159% between 1989 and 2018, mainly due to reductions in water (−61%), active bar (−35%), and bare soil surface areas (−29%). The changes were evident ten years after plant operations began and intensified during the period known as the megadrought in central Chile (2008–2018). The flow magnitudes present a decrease for exceedance probabilities (P) below 85% in the period after 1985, with a slight increase recorded for low flows (P > 85%). In the segments with superior stabilization, invasive species such as Acacia dealbata (silver wattle) predominated, which are specialists at taking advantage of disturbances to settle and stabilize active areas, narrowing the possibilities for morphological change.
Detecting and quantifying hydromorphology changes in a chilean river after 50 years of dam operation
This study identifies and characterizes hydromorphological changes along the Rapel River downstream of the first large dam built in Chile (1968). A hydromorphological analysis is carried out to assess changes on the hydrological flow regime, bed sediments, and fluvial morphology along a 19 km river reach. Results classify current global hydrological quality as “Moderate” (according to the Indicator for Hydrological Alteration in RIverS, IAHRIS), however specific indicators within this classification scheme identified quality as “Poor”. The morphological quality decreased from “Very Good” to “Good” (assessed by the Morphological Quality Index, MQI). Changes in the planform were particularly intense during the post dam period when intensive lateral mobility occurred, with the corresponding loss of secondary river branches, and with generation of straighter and regular river sections with presence of an armor layer observed along the entire river reach. Between 1991 and 2015 channel stabilization with less lateral mobility was observed, which thought to be associated with the river new equilibrium trend. River width, sinuosity and braiding index changed at different rates along the studied river reach. Our investigation demonstrates that the Rapel River experienced changes differently than those described in the literature given its lower gradient and hydraulic interaction with the Pacific Ocean.