Composition and classification of salts in surface water and groundwaterin a semi-arid irrigated area - Case study in Mirzaabad district, Uzbekistan -

摘要

The Mirzaabad district in the Syrdarya Region of Uzbekistan has a secondary soil salinization problem due to excessive irrigation and increased salt contents in shallow groundwater. This district is separated into the Old and New zones according to history and circumstances of irrigation development. The Old zone is located near the Syr Darya River, has abundant water and has been irrigated for centuries. In contrast, the New zone, located in the Golodnaya steppe, was developed into irrigated farmland through the use of concrete canals and subsurface drainages, and is prone to water shortages. The main drainage canal (main collector) is located near the boundary of these zones.In this study, we estimated the salt compositions of surface water (irrigation and drainage water) and groundwater in this district, and characterized the different types of mineral species using the chemical equilibrium model Visual MINTEQ. The groundwater composition differed between the two zones, with calcium and magnesium salts dominating the Old zone, and sodium salts dominating the New zone. This difference may result from highly-soluble sodium salts being discharged from the Old zone through theopen channel drainages; whereas sediment continues to accumulate in subsurface drainages in the New zone, reducing drainability and discharge of sodium salts, causing them to infiltrate into the shallow groundwater.