Keywords: 
• vertical circle of water /
• groundwater system /
• ecological effect /
• SPAC system,GSPAC system /
• inland basin /
• Northwest China /

Abstract: The inland basins in northwest China are of the four great regions short of hydrological cycles in China.By the vertical circle in the water saturation,the water in aeration zone,the water in aerosphere near surface,and the water in plant body(‘Four Waters'),the groundwater systems have indispensable adjective effects on maintaining the balance among water,heat and salt in shallow surface,the surface ecological balance,the long-term availability of soil resources and the relative stability of the local climate.At present,the related study pays more attention to the statistical analysis of corresponding relation-ship between groundwater and vegetation types,but less to the mechanism of water fluxion.Although more and more research on soil-plant-atmosphere continuum(SPAC) system has been carried out,little improvement has been achieved in the ecological effect of groundwater because of the hard scale-transform and the ignorance of the effect of groundwater in simulation.In contrast to SPAC system,the groundwater-soil-plant-atmosphere continuum(GSPAC) system is more integrated.To make clear the ecological effect of groundwater on arid inland basin and guide the exploitation of water resources,such studies should be carried out:(1) the dynamic course and the mechanism of the vertical circle between ‘Four Waters',especially the dynamic transition model about water,steam and heat through interface between saturated zone and aeration zone; and(2) the evolution characters of groundwater system under human activities,which is the key to the transform from microcosmic SPAC system to macroscopic water resources management.