Mathematical modeling of nitrate and salinity along the Rosetta Branch in the Nile Delta

Abstract

A physico-chemical water quality model has been developed and tested for the Rosetta Branch in the Nile Delta. This paper discusses the set up of this model, the investigation on sufficient availability of water quality sampling and pollution data to enable such Modeling exercise, the extensive model verification by statistical techniques, as well as the model refinement and scenario analyses carried out by the model. The model has been set up making use of the MIKE 11 river Modeling software. The physico-chemical water quality (WQ) model is linked with a detailed full hydrodynamic (HD) model developed for the same Rosetta branch, and also implemented in the MIKE 11 Modeling system. All significant pollution sources along the Rosetta branch were considered. Pollution along the Rosetta Branch mainly originates from the drains. Three drains (El-Moheet, Sabal, and Tala) are monitored with different water quality variables measured on monthly basis. The measured concentrations for the Modeled variables and the discharges along the drains and at the model boundaries are used as model inputs. In between the different instantaneous values for these observations, linear interpolations are made. The model was calibrated and validated based on the available sampling data along the Branch. Given the data limitations for calculation of the model input and for model calibration, the simulation results can be considered good. The paper focuses on the model results for NO3-N and TDS, and links the results towards their use in water management applying the combined HD-WQ model as integrated decision support tool. This was illustrated in the paper by prior simulation of scenarios in the model.