Water is one of the most important sources of economic development. In order to maintain living conditions, attention must be paid to water quality management, water pollution control and environmental protection. The pollution of the Nile river has increased recently due to population growth, economic development and related human activities. Egypt is among the 10 countries that will suffer from water scarcity by 2025 due to rapid population growth. This study aimed the assessment of water quality according to drinking, agriculture and aquatic life purposes in El-Sinbellawein city and some of belonging villages, at Dakahlia governorate, Egypt. The water quality indices are an attempt to represent overall quality of water. Assessment of water quality for treatment plants under study according to drinking and aquatic life purposes was carried out using weighted arithmetic method of water quality index (WQI). Physico-chemical parameters of different water treatment plants at different locations were analyzed before and after water treatment and the obtained values were used for calculation of Water Quality Index (WQI). The values of WQI showed that the water is unsuitable in some treatment plants and excellent in another for drinking and aquatic life. Sodium adsorption ratio (SAR), percent sodium (Na %), residual sodium carbonate (RSC), Kelly Index (KI) and magnesium ratio (MR) were also calculated by using major anions and cations values to assess suitability of water for irrigation. The results indicated that all treatment plants under studying were classified from suitable to excellent for irrigation purposes. The study was extended also to include assess of water pollution by metals (Cd2+, Cu2+, Fe2+, Mn2+, Ni2+, Pb2+, and Zn2+) via calculation of Metal index (MI) and pollution index (PI). The results indicate that there is no effect of metals in the case of water use for agricultural purposes, whereas for drinking and aquatic life, all measured metals except Zn2 + and Ni2 + show different degrees of contamination. The wastes should be treated before disposing and dumped to suitable sites, to protect the water quality from deterioration and maintain its quality.