Morphometric parameters and the limnological status of the Calima reservoir, Valle del Cauca, Colombia

Abstract

Introduction: The bathymetry of the Calima Reservoir has changed considerably since its construction, as evidenced by the loss of useful volume, reduced depth, and morphological alterations caused by sediment accumulation in the tail waters and changes in terrestrial biotopes associated with the water surface.
Objective: To determine the bathymetric structure of the reservoir in 2023 and identify the spatial domains most affected by the entry of contaminants that may promote the growth of algae and cyanobacteria, potentially compromising the use of the water for recreation, aquatic sports, and sport fishing.
Methodology: In April 2023, a bathymetric profile was surveyed in a zigzag pattern across the reservoir using an echosounder with a transducer and GPS. The field data were organized in Excel and integrated into ArcGIS Pro 3.1.3 to generate the bathymetric layout and calculate physical parameters.
Results: Three zones were defined. Zone A: the main deposition area at the inlet of the Calima River, containing the shallowest isolines; two streams converge here, carrying most of the wastewater from the municipality of Calima El Darién, where algal blooms have been reported. Zone B: a narrow strip with depths ranging from 40 to 60 m. Zone C: the dam area, with depths close to 70 m.
Conclusions: The reservoir has an elongated shape aligned with the flow axis of the Calima River. Upon entering, the river loses horizontal energy and deposits suspended solids, forming a lentic zone that narrows toward the dam. The dendritic zones remain isolated from the main axis, and Zone A receives the highest load of urban discharges, favoring the proliferation of phytoplanktonic algae.