Modeling water quality in a tropical reservoir using CE-QUAL-W2: handling data scarcity, urban pollution and hydroclimatic seasonality

ABSTRACT This study applies a 2-D hydrodynamic model (CE-QUAL-W2) for simulating water quality dynamics in tropical reservoir located Fortaleza, Ceará, Brazil. While rainfall concentrates basically the first semester, this receives untreated sewage from an urban catchment throughout year. To deal with data scarcity, simplifications are justified and several adjustments carried out, so that only parameters temperature (T), dissolved oxygen (DO), chlorophyll (Chla) phosphate (PO4) kept modeling process. Additionally, different assumptions performed regarding time-evolution of inlet concentrations: constant values, step linear variations. The results indicate simplified can predict well seasonal variations T, DO, Chla PO4. best fitting between measurements obtained assumption variation concentrations, followed by values variation. Moreover, reveal while PO4 presents complete mixing behavior clear increase concentration wet to dry season, DO show alternating stratification-destratification patter during day-night but without relevant Model simulations scenarios also significant reduction second external load has stronger impact on outputs than hydroclimatic variability. approach developed present is proposed as simple way cope pollution seasonality reservoirs.