GIS approach for the evaluation of water resources quality indicators of the Aydar-Arnasay Lakes System in Uzbekistan

The geolocation of the Aydar-Arnasay Lake System (hereinafter, AALS) is in the middle reaches of the Syrdarya River, south of the Shardara Reservoir (Kazakhstan), and connected to the Kyzylkum Desert. The quality indicators of the AALS water resources have changed over the years with reference to the composition of the Syrdarya River water outflow from the Shardara Reservoir and the discharge of collector-drainage water (hereinafter, CDW) from irrigated lands into the lake system. Thus, this study aims at evaluating the changes in the space–time chemical composition of the AALS water resources by integrating conventional physicochemical methods and GIS technologies. According to the number of samples, 465 water samples from 164 points from the AALS were collected. The low-mineralized but heavy metal-bearing CDW has been discharged into the AALS, leading to an increase in the nitrogen and heavy metals concentration in the lake system water resources and requires constant monitoring of their content. However, the mineralization of the CDW is relatively lower than the mineralization of the main water bodies of the AALS, and this water is important in stabilizing the hydrochemical state of the lake system. An increase in the concentration of heavy metals and other chemical substances in the AALS relative to the standardized governmental permissible norm could cause bioaccumulation in existing fish species and adversely affect the public health, accruing toxic elements as an aftermath of biomagnification.