Abstract: Research on spatial and temporal variability of regional groundwater quality is not only an important content of water quality evaluation, but also is the basic and premise for management decisions of groundwater utilization and protection. In this study, the 10-years data of groundwater quality from 2005 to 2014 were used to analyze the spatial and temporal variability of groundwater quality in Naiman region of Horqin Sandy Land. The results showed that the 10-years average value of each index was lower than national groundwater quality Ⅱ class standards, but pH、NO₃^- and COD_cr exceeded national groundwaterⅡclass standard in some areas, in general, the water quality in this region was better. There were an obvious positive correlation between the regional TDS with Ca²⁺, Mg²⁺, Na⁺, HCO₃^-, SO₄²⁺, COD_cr, additionally, TDS increased with increasing Ca²⁺, Mg²⁺, Na⁺, HCO₃^-, SO₄²⁺, COD_cr, the concentration of major water quality index were on the decline over time, SO₄²⁺, Na⁺, TDS, HCO₃^- were relatively stable over time, but Ca²⁺, NO₃^-, Mg²⁺, Cl^-, PO₄^3-, COD_cr had significant changes during the 10-years period. The concentration of Ca²⁺, Mg²⁺, HCO₃^-, SO₄²⁺, TDS were the sequence of farmland non-irrigation well>farmland irrigation well>sand gauging well, Na⁺, COD_cr were the sequence of sand gauging well >farmland non-irrigation well >farmland irrigation well, NO₃^- was the sequence of sand gauging well> farmland irrigation well> farmland non-irrigation well. The changes of groundwater quality in this area mainly depend on the carbonate karst solution, the pesticides and fertilizers utilization, and the industrial and living sewage discharge.

Key words: Naiman region, groundwater quality, spatial and temporal variation