Tracking pollution and its sources in the catchment-lake system of major waterbodies in Kazakhstan

The objective of the present study was to identify the sources and routes of entry of heavy metals and nutrients into several large waterbodies in the arid zone of Kazakhstan, namely Lake Balkhash and Samarkan and Shardara reservoirs. A data visualization method was used for this purpose. Statistical mapping, based on referencing coordinates of the material selection points, was performed with the Statistics 12.0 program. Matching statistical maps with the waterbody contours was performed in Adobe Photoshop. Maps of the spatial distribution of heavy metals (cadmium, nickel, cobalt, lead, zinc and copper) and nutrients were constructed for all three study waterbodies. Data visualization clearly illustrated the relationship between the distribution of pollutants in the study waterbodies, as well as the sources of anthropogenic pollution. Based on the mapping exercise, it was established that Cu and Zn entered the waterbodies mainly in agricultural waste waters, while Cd, Ni, Co, Pb and partly Zn entered the waterbodies mainly in industrial and surface run-off. Nutrients enter the waterbodies mainly in river and municipal waters. The constructed maps demonstrate the role of the constant flow in the distribution of pollutants in the waters of Lake Balkhash. The results also indicate that statistical mapping is an effective tool for identifying the sources and routes of pollutant entry into waterbodies. The imposition of statistical maps on the contours of waterbodies of concern provides a mapping method allowing for more visually compelling data and information for a wide circle of users and managers.