SOME ASPECTS OF WATER QUALITY MODELING FOR THE NILE RIVER FROM ASWAN TO CAIRO, EGYPT

摘要

Water is delivered in Egypt through the Nile River and huge network of canals in order to sustain the water demands of the population. Most of the drainage water flows back through open drains and tube outlets to the Nile River in the reach from Aswan to Cairo that has a length of 957 km. Because the drainage water is contaminated from agricultural, domestic and industrial wastes, stress is put on water users, managers and decision makers. The water quality status is assessed especially the spatial and temporal effects of the various sources of pollution on the Nile environment. A mathematical model is developed and applied to the Nile River reach from Aswan to Cairo. The model solves the advection-dispersion transport differential equation using the finite element method. The model is applied for prediction of major quality parameters originating from agricultural and domestic pollutants. The parameters considered are the Biological Oxygen Demand (BOD) that comes mostly from domestic pollution, and the Total Dissolved Solids (TDS) and Chlorides (Cl) that come mostly from agricultural and industrial pollution. The reach of the Nile from Aswan to Cairo is divided into 5000 elements with element length (grid resolution) of about 200 m. The number of monitored point sources of pollution considered herein is 76 in 1997 and 89 in 1998. The data were measured by the Nile Research Institute, Egypt. In the model calibration, the distributed loads or non-point sources are assumed so that reasonable match occurs between the model predictions and the measured concentrations using the data of December 1997 (a low flow period). In verifying the developed model, the predictions compared well with the June 1998 (a high flow period) concentrations despite lack and uncertainty of some data, especially industrial point source flows and distributed loads. The model can be used in examining the various management practices on the water quality conditions of the Nile River and similar open channels and rivers.