【正文】 r contamination has resulted from leaching of nitrates from fertilizers and bacteria from livestock and feed wastes. Agricultural pesticides are both a potential diffuse source of water contamination. Since the construction of the High Aswan Dam, the water quality of the Nile became primarily dependent on the quality and ecosystem characteristics of the Lake Nasser reservoir and less directly dependent on the water quality of the upper reaches of the Nile. Water released from the Lake Nasser generally exhibits the same seasonal variation and the same overall characteristics from one year to another. Downstream changes in river water quality areprimarily due to (i) the hydrodynamic regime of the river, regulatedby the Nile barrages,(ii) agricultural return flows, and (iii) domestic and industrial waste discharges including oil and waste from boats. These changes are more pronounced as the river flows through the densely populated urban and industrial centers of Cairo and the Delta regioni91. Nile Research Institute of the National Water Research Center is intensively involved in the monitoring of water quality of the River Nile and its branches. All the pollution parameters are to be measured according to the updated edition of the American Standard Methods for Examination of Water and Wastewater.ENVIRONMENTAL IMPACT As a result of poor wastewater treatment, high concentrations of coliform bacteria are found in the Nile and its branches downstream of Cairo. Values of 1 to 10 million (Most Probable Number) MPN/100 ml, have been measured in the Rosetta branch. This is far above the standard of five thousand MPN/100 ml, as given in Law 48 of 1982. Since exposure to pathogenic bacteria can cause serious health problems, adequate treatment of sewage should be given high priority. High concentrations of pesticides are found in the Nile and Rosetta Branch. Forexample, the reported concentration for linadane (yHCH) and DDT are 5 to 10 times above European standards. As agricultural activities are the principal source, it is expected that concentrations in agricultural drain are even higher. The risk of pesticides relates to drinking water supply without proper treatment (by means of active carbon) and the accumulation in fish products. The problem asks for a sound baseline study, including a review of pesticide use, import and production and measured concentrations in variouswater booddiieess,，with special attention given to drinking water resources and fishing immediate, actions mightbe necessary m case unacceptable concentrations are found in drinking water. Although various studies and monitoring efforts have been carried out, information on water quality status, its causes and effects shows many gaps. To enable the formulation of effective measures to prevent further pollution of the vital water resources and to restore polluted areas, more detailed information is required for pollution sources, the transport and behavior of pollutants in the water system, the assimilative (selfpurification) capacity of the water system, and the impacts of pollutants on various water uses. This calls for an adequate routine monitoring system, a data base and information system and an integrated modelingapproach, to analyze the impact of individual pollution sources on ambient water quality, to evaluate the efficiency of proposed actions. The design of the monitoring system could be as follows: (i) early warning system (EWS): an early warning system is remended. The sensor system will receive and send information to a central processing unit. There can be online measurement equipment, the general public observing calamities, the police officially involved in all kind of accidents and the eventual polluters, which then have a legal obligation to report environmental accidents。 4 factories collect their wastewater in I lying in the vicinity of the treatment plants。 AssessmentINTRODUCTION The ava