Eutrophication still belongs to the serious problems waiting for solution. Phosphorus is the nutrient most often limiting the primary producers. It is well known, the improvement of water quality can be, after successful decrease of external P load, retarded by P-release from sediments. It is also necessary to realize, that the decrease of external P-load to the demanding level cannot be due to technical, political or economical reasons always possible. Measures increasing P-retention in sediments are often employed in such conditions. Many cases are known when the level of the water quality improvement remained far behind the expectations. Technical problems, still unknown mechanisms or insufficient screening followed by inadequate solution might be the reasons for the failures. The aim of this paper is to show simple decision-support system for exclusion of improper solutions and increase of the effectiveness of activities made before the rehabilitation measures realization