Developing a water quality index in a tropical reservoir using a measure of multiparameters

A water quality index (WQI) for the Adolfo López Mateos Dam (ALMD) was developed based on statistical multiparameter tools assisted with linear programming. ALMD was selected due to its social and economic significance in Sinaloa, the state with the highest agricultural production in Mexico. Twenty-six water-quality parameters were analyzed for four sampling points distributed along the dam during 2012–2017. The data were analyzed using Pearson's correlation matrix, principal components analysis (PCA) and sensitivity analysis (SA). Results indicated that variables explaining spatial and temporal water quality distribution at ALMD were total suspended solids, fecal coliforms, pH, dissolved oxygen, chemical oxygen demand, nitrate nitrogen, organic nitrogen, ammonium nitrogen, total phosphorus, orthophosphates and chlorophyll a. A series of pondering weights (Wi) were obtained from the PCA analysis. Every Wi was multiplied by the probability function of the specific parameter (SIi) to generate the WQI_ALMD model. The model was applied to address water quality at ALMD which describes the general overall water quality in the dam as ‘good’. Finally, a sensitivity analysis for the model showed that the most sensitive WQI variables were: fecal coliforms, total phosphorus, organic nitrogen, and chlorophyll a.