Water Quality Assessment Using the Water Quality Index (WQI – IDEAM) in the Lower Basin of the Cesar River, Colombia

Abstract

Introduction: Water is one of the most important natural resources for life on Earth and constitutes a cross-cutting axis for the sustainable development of societies. Its availability, distribution, and quality directly influence public health, food security, biodiversity, economic productivity, and the overall well-being of human communities. The quality of surface water is a subject of international debate, primarily due to anthropogenic pollution levels, which are often harmful to the natural self-purification processes of water bodies and difficult to address through conventional chemical treatment. The Cesar River plays a key role in the surrounding areas of the Cesar Department and parts of La Guajira Department, serving as a central source for economic activities such as agriculture, fishing, livestock farming, and material extraction. These activities have altered the ecosystems associated with this natural water source.

Methods: This research was conducted using a quantitative approach, with a non-experimental and longitudinal design. The study area corresponds to the lower basin of the Cesar River, near the Zapatosa marsh complex, specifically within the jurisdiction of the municipality of Chimichagua, Cesar Department. Four strategic sampling points were selected along a 6.25-kilometer section of the river. This stretch begins at the river port located in the village of Saloa (Chimichagua), where various physicochemical and microbiological parameters were measured to determine the Water Quality Index (WQI) as proposed by IDEAM (2020). These parameters included: dissolved oxygen (DO), total suspended solids (TSS), chemical oxygen demand (COD), pH, electrical conductivity, nitrates, fecal coliforms, and total phosphorus.

Discussion y Conclusions: The assessment of water quality in the lower basin of the Cesar River using the Water Quality Index (WQI) methodology established by IDEAM (2020) revealed unfavorable conditions for the use of the resource for human consumption. The comprehensive analysis of physicochemical and microbiological parameters showed that high levels of suspended solids, turbidity, BOD, COD, phosphates, nitrates, and fecal coliforms are closely associated with anthropogenic activities such as intensive agriculture, extensive livestock farming, untreated wastewater discharges, and material extraction from the riverbed.