Egyptian Computer Science Journal Vol. 39 No. 4 September 2015 ISSN-1110-2586 -56- Proposed Decision Support System for Reduction of Total Phosphorus in Lake Manzala Alaa El Din Mohamed El-Ghazali 1 , Abeer A. Amer 1 and Mustafa, M. M. 2 1 Computer and Information Systems Department, Sadat Academy for Management Sciences (SAMS) 2 Fish Rearing Lab., Aquaculture Division, National Institute of Oceanography and Fisheries (NIOF) a.elghazali@gmail.com, abamer_2000@yahoo.com Abstract In Egypt, Lake Manzala has great economic importance as a major source of fish and salt. It is a natural resource and is considered highly important in terms of its socio-economic aspects. It has suffered from a high level of eutrophication, due to the heavy load of nutrients, especially phosphorus. Reduction of Total Phosphorous System (RTPS) has been conducted to solve the high level of eutrophication and pollution problems of Lake Manzala, which are unstructured and complex. The main component of RTPS is the inclusion of RTP model. Actually, this is a quantitative and dynamic model whose objective is to simulate the mass balance of TP in water and sediments in order to optimize the ecosystem of Lake Manzala. This model is considered as a useful water quality management tool in designing TP two reducing scenarios. The first scenario is the reduction of TP concentration in water drains, and the second scenario is the reduction of TP concentration in water drains and Lake Sediment. Furthermore, in each scenario there are multiple alternatives through ratios of reduced TP. It found that 30 % reduction of TP from each drain could act as an important solution for quick recovery of the lake condition to reach 560.56 mg.m -3 of TP’s initial concentration (1590 mg.m -3 in spring season) after 10 days and a maximum 433.37 mg.m -3 after 100 days. Keyword:DSS, Simulation, Modeling, Total Phosphorus, Ecosystem, Eutrophication, Lake Manzala 1. Introduction Decision Supports Systems (DSS) are computer-based information systems designed in such a way that help decision maker to select one of the many alternative solutions to a problem. It helps organization to increase production, reduce costs, increase profitability and enhance quality. It is an interactive system with an organized collection of models, people, procedures, software, databases, telecommunication, and devices, which helps decision makers to solve unstructured or semi-structured problems [1]. Lake Manzala is the largest lakes northern coastal lake of Nile Delta and is considered highly important in terms of geographical, social and economic aspects. where, the lake lies within the borders of five Egyptian governorates Damietta, Port Said, Ismailia and Sharkiya Dakahliya, and Its annual fish production represents about half of the total fish yield of the northern Delta lakes, and about one fifth the (non-marine) fish yield of Egypt [2]. In addition, it is the largest lake in terms of fish production in Egypt with an annual output of 60 thousand tons (35% of fish production of other lakes). Lake Manzala suffered from a high level of eutrophication, due to the heavy load of nutrients, especially phosphorus and nitrogen compounds due to agricultural run off, sewage and drains discharges [2].