This work proposes a water quality model based on the pooled effects of nitrate, nitrite, ammonium, and orthophosphate concentration as the main causatives of environmental water quality changes. One of the main characteristics of the model is assigning an environmental weight for each variable (zeta(i)) according to threshold concentrations of nutrients capable of inducing water changes condition. The model validation demonstrated adequate sensitivity to different data arrangements; as observed in an arid climate bay, showing annual stratification resulting in a variable content in nitrogen-forms and phosphorous. The model can be continuously calibrated over time by adding more N and P data to specific nutrient functions, and tested on sites with high NO(3), NO(2) or NH(4) concentrations.