| ABSTRACT | The Egyptian Mediterranean coast is featured by the system of coastal lakes stretching along the major part of it. This system consists of Lake Mariut, Lake Edku, Lake Burullus and Lake Manzalah from west to east respectively and known as the northern Egyptian Delta Lakes. These Lakes vary in their surface areas; with Lake Mariut being the smallest (about 55 km2) and Lake Manzalah being the largest (about 700 km2). Water, nitrogen and phosphorous budgets of Lake Manzalah have been calculated using data collected during January-December 2012.The main positive contributor in the water budget of Lake Manzalah is the drainage water being 6692.6x106 m3/yr. The annual rainfall is 26.53x106 m3/yr and the evaporation is 1075.6x106 m3/yr. The net annual amount of outflowing water from Lake Manzalah to the Mediterranean Sea is 9503.23x106 m3/yrand the net amount of seawater invading the Lake estimated is 3895.76x106 m3/yr. Accordingly, the net water exchange between Lake Manzalah and the Mediterranean Sea was 5607.47x106 m3/yr seaward negatively affects the water budget of the lake. The nutrient salt load of the nitrogen load in the lake from the drainage water is estimated to be 1381.09 tons/year and that from the rain 3.703 tons/year. The amount of nitrogen load transported to the sea through Boughaz El-Gamil being 1025.753 tons/year, while the inflowing nitrogen load is estimated to be 180.147 tons/year. The phosphorus load from ,the drainage water is estimated to be 2212.67 tons/year and that from the rain 8.546 tons/year. The amount of phosphorus load transported to the sea through Boughaz El-Gamil being 680.668 tons/year, while the inflowing phosphorous load is estimated to be 101.687 tons/year. The components of nitrogen and phosphorous budgets given from the present study in Lake Manzalah are high compared to the results previously calculated for the period 1984-1985. This is may be due to the pronounced increase in the land reclamation processes around the Lake, which use the nitrogenous fertilizers, which, in turn, are washed with the agriculture drainage water into the Lake. This is beside the sewage wastes from human activities and fish farms. The impact of the climate change on the water, nitrogen and phosphorus budgets of the lake and their effects on the population of the surround area was also discussed. |