In the Government Decision no. 932 of 20.11.2013 establishes a complex multi-annual system for quantitative and qualitative assessment of surface and groundwater by using procedures and technical measures for sampling, analysis and synthesis, in order to sustainably manage and capitalize on aquatic resources. In the list of standard methods lacks non-ionized ammonia, toxic to aquatic biota, and surface water quality index, although many organic and inorganic pollutants are present in surface and groundwater, including nitrogen. In order to ensure the monitoring of non-ionized ammonia (NH3) and the determination of the surface water quality index, the Institute of Ecology and Geography has developed the standards: 1. SM 353: 2020. Water quality. Determination of ammonia (NH3) content. Calculation method. 2. SM 354: 2021. Water quality. Determination of surface water quality index. Calculation method. The method of calculating the ammonia (NH3) content was used for the surface waters of the republic. In the water of the right tributaries of the fl. Dniester the ammonia concentration admitted in the Government Decision no. 802 of October 9, 2013 of 0.025 mg/dm3, at a temperature of 50C and 150C, was exceeded in different years by 1,04 – 131,2 times. Exceeding the permitted requirements of NH3 reaches about 288 times in the left tributaries of the Prut River, and in the surface waters of the Danube-Prut and Black Sea river basin, the content was exceeded 1,04 – 272,4 times. The NH3 concentration calculated in the water of the Lower Dniester and in the Unguri-Holoşniţa Wetland was at the limit of 0,025 mg/dm3, and in the water of Beleu Lake, Slobozia Mare village, and in Manta Lake with non-essential exceedances of the value of maintaining fish life.