This research aims at studying the most important indicators of water pollution leading to nutrient increase (eutrophication) in AL- Basel Dam Lake, and connecting them with pollution sources represented by untreated sewage water and agricultural drainage water, including rain water coming from the lands surrounding the lake. Among the most important of these indicators are total phosphorus (TP) and total Nitrogen (TN). Samples were taken and analyzed from four sitesof the lake (S1, S2, S3, S4) were conducted periodically. The work continued to conduct tests for full hydrological cycle as of January (2016) until December (2016). The study showed that the lake was highly fertilized according to the (TN- TP) this indicates that the lake is affected by the pollutants it encounters, especially the wastewater pollutants. The specific component of algal growth was determined by knowing the ratio between total nitrogen and total phosphorus. The TN / TP ratio was greater than 10, so total phosphorus is the specific component of algal growth in the Basel DamLake.