Water Quality Assessment, Water Quality Index, WQI, Chahnimeh Reservoirs

Assessing the quality of water resources and having accurate information about their quantity and quality is a prerequisite for water resources management. Considering the importance of the Chahnimeh reservoirs of the main source of drinking and agricultural water supply in Sistan, it seems necessary to evaluate the water quality of the No.1 Chahnimeh, which is the most important and the largest lake among the triple Chahnimeh reservoirs. Today, one of the most important methods to determine the quality of water in simple terms is the use of water quality indicators. This research was conducted during one year based on seasonal sampling from September 2020 to September 2021. The factors of nitrate, nitrite, dissolved oxygen, electrical conductivity, hardness, and pH were measured in eight sampling stations and the WQI index was calculated using them. In general, according to the numbers of the water quality index, the water quality in all stations, and sampling periods has not gone out of the range of good quality waters (50-100), and the range of changes is such that the water quality is favorable for human use. The highest numerical value of the quality index was recorded in the winter. The middle points of the lake have better quality compared to the peripheral parts and the inlet and outlet of the reservoir. It is worth noting that due to the increasing importance of Chahnimeh reservoirs and the trend of changes in the type of water consumption of these valuable resources, it seems necessary to carry out more detailed investigations, continuously evaluate and monitor the water quality, and design a water quality monitoring model for these sources.