Water quality within the Rio Chone estuary, a seasonally inverse, tropical estuary, in Ecuador was characterized by modeling the distribution of biochemical oxygen demand (BOD) and dissolved inorganic nitrogen (DIN) within the water column. These two variables are modeled using modified advection-diffusion equations within a two-dimensional, laterally-averaged hydrodynamic model.

The model includes sources of salt, BOD and DIN from shrimp mariculture ponds in the region surrounding the estuary. The model was successful in simulating seasonal concentrations in DIN and BOD over a range in source concentrations. Seasonal BOD measurements along the length of the estuary were coincident with dissolved oxygen concentrations in the estuary (high BOD generally corresponding to low dissolved oxygen). Results suggest that the citing of shrimp ponds near the head of the estuary should be avoided in order maintain estuarine water quality and to maximize production.