Effect Of Land Use And Cover Change On Groundwater In Arid Area

Heihe river basin is an important part of arid land in north-west region, locates at transition of three physical geography zone, it is sensitive and eco-fragile region of environment evolution. The hydrological effect of land use/cover change shows great spatial-temporal heterogeneity, the land use/cover changes have significant effect on groundwater system and regional water resource. The water resource characteristics of arid region leads that the groundwater play an important role in arid area, and the groundwater resource becomes one vital factor to oasis system. In the study area, the agriculture economy is the core of oasis economy, 83% of agriculture economy is limited in oasis zone. This typical oasis economy structure impels more compact relationship of water resource and land use forming.Land use has significant effect on groundwater resource, and the land use changes the natural hydrologic cycle way of groundwater system. All the processes of land use effects not the groundwater recharge, but also the groundwater quality. In this paper, the author use data from 68 wells to analyze the groundwater variation by using Arc-GIS technique in recent 20 years. The groundwater level is in continual decreasing duration, the decreasing rate is from above 0.5m/a at the foot of southern mountain to 0.1m/a at spring spillover area progressively; the land use change leads that groundwater reserves decreases 0.55×10⁸m³/a averagely in this region; and because of the historical land resource exploration, the groundwater mineralization has significant amplitude, it increases from 500mg/L at the alluvial fan to 2100mg/L near Zhengyi gorge, and the groundwater quality changes from I to III, even reaches IV in some area; water salinization also increases accordingly, it changes from HCO₃^- type to SO₄^2- or Cl^- type, the future water environment is not optimistic. The study results indicate that the groundwater resource system in this region is fragile and become more exacerbating under human activities. The land use pattern has influence to the cycle way of groundwater system, and the groundwater quality shows badness trend.Understanding the relationship between land use/cover change and region groundwater system can help us to set up one land use mode propitious to groundwater protection and reasonable utilization, can impel plan and management of water and land resources using more scientific and rational in Heihe midstream region.