Sediment budget analysis of the Guayas River using a process-based model

Abstract

Abstract. The Equatorial Daule and Babahoyo rivers meet and combine into the tidal Guayas River, which flows into the largest estuary on the Pacific coast of South America. The city of Guayaquil, located along the Guayas, is the main port of Ecuador but, at the same time, the planet's fourth most vulnerable city to future flooding due to climate change. Fluvial sedimentation, which has increased in the recent years, is seen as one of the factors contributing to the risk of flooding. The planning and design of effective mitigation measures requires a good understanding of the causes which have led to the current hazards. In this study, the process-based Delft3D FM model was used in order to explain the dominant processes in the river and the effects that past interventions along the river and its estuary have had in the overall sediment budget. Additionally, a simulation including sea level rise was used in order to understand the possible future impact of climate change on the sediment budget. Results indicate that the increased import of marine sediment is the result of the recent increase in tidal asymmetry due to land reclamation and a decrease of episodic flushing by river floods due to upstream dam construction. This is in contrast with the local perception of the problem, which ascribes sedimentation to deforestation in the upper catchment. Only the deposition of silt and clay in connected stagnant water bodies could perhaps be ascribed to upstream deforestation.

Evaluating the Sensitivity of Multi‐Dimensional Model Predictions of Salmon Habitat to the Source of Remotely Sensed River Bathymetry

“…We evaluated the model's sensitivity to this parameter by varying the eddy viscosity between 0.1 and 1 m 2 /s and found that a value of 1 m 2 /s provided the closest agreement with measured velocities. While this value is high it is within the range of values reported in the literature for Delft3D‐FM models (Barrera Crespo et al., 2019; Martyr‐Koller et al., 2017; Willemsen et al., 2022). The specified eddy viscosity value maintained model stability and successfully reproduced the flow fields.…”

Conservation agriculture can help the South American Andean region achieve food security

“…Upstream erosion lowers water quality and leads to siltation and associated flooding downstream (Barrowclough et al., 2016; Barrera Crespo et al., 2019; Restrepo & Escobar, 2018; Rosas et al., 2020). Climate change will not only affect the sustainability of soils in the higher elevations but will also impact lower elevation areas, where siltations will reduce water storage and create greater potential for flooding (Barrera Crespo et al., 2019).…”

“…Water runoff from Andean highland farming areas feeds some of the larger river systems draining into the Pacific Ocean. For example, the Chimbo river watershed in highland Ecuador provides about 40% of the water to the Guayas River, undoubtedly the most economically important river system in Ecuador as it serves as a source of water for industries, large cities, and agriculture; provides a means of transport; and flows to the Gulf of Guayaquil, which is the largest estuarine ecosystem on the Pacific coast of South America (Barrera et al., 2012; Barrera Crespo et al., 2019). Upstream erosion lowers water quality and leads to siltation and associated flooding downstream (Barrowclough et al., 2016; Barrera Crespo et al., 2019; Restrepo & Escobar, 2018; Rosas et al., 2020).…”

“…For example, the Chimbo river watershed in highland Ecuador provides about 40% of the water to the Guayas River, undoubtedly the most economically important river system in Ecuador as it serves as a source of water for industries, large cities, and agriculture; provides a means of transport; and flows to the Gulf of Guayaquil, which is the largest estuarine ecosystem on the Pacific coast of South America (Barrera et al., 2012; Barrera Crespo et al., 2019). Upstream erosion lowers water quality and leads to siltation and associated flooding downstream (Barrowclough et al., 2016; Barrera Crespo et al., 2019; Restrepo & Escobar, 2018; Rosas et al., 2020). Climate change will not only affect the sustainability of soils in the higher elevations but will also impact lower elevation areas, where siltations will reduce water storage and create greater potential for flooding (Barrera Crespo et al., 2019).…”