An Input/ Output Flux Model of Total Phosphorous in Lake Edku, a Northern Eutrophic Nile Delta Lake

2 Abstract: Previous studies conducted on the hydrography, chemical and biological characteristics of Lake Edku; one of the northern Nile Delta Lakes, concluded that this lake suffered from a high level of eutrophication, due to the heavy load of nutrients, especially phosphorus. Before deciding what type of treatment should be used for decreasing total phosphorous (TP), knowledge of the sources and sinks of this nutrient within the lake should be studied. A water-sediment flux model for TP was implemented in this study to understand its geo-chemical behavior across water and sediments boundary and to calculate its concentration in the whole lake water volume (P ) and sediment volume (P ) as a result of discharging loads. The resulting seasonal 12 budgets showed that the TP input values to Lake Edku (from drains and re-suspension process) were more than the output values (out flowing and settling) in the four seasons of the year. These reflect the imbalance (an accumulation) of TP in the geo-chemical cycle inside the lake and indicated that this lake is in a highly eutrophic status. This model was considered as a useful water quality management tool in designing TP reducing scenarios, especially with high discharging loads. It was found that 2% reduction of TP concentration in the lake sediments and 15 % reduction of TP from each drain could act as an important solution for quick recovery of the lake condition to reach 20% of TP's initial concentration after 100 days and a maximum of 8% after 500 days.