Shallow groundwater dynamics and its driving forces in extremely arid areas: A case study of the lower Heihe River in northwestern China
Shallow groundwater is an important source of water for the maintenance and restoration of ecosystems in arid environments, which necessitates a deeper understanding of its complex spatial and temporal dynamics driven by hydrological processes. This study explores the dominant hydrological processes that control the shallow groundwater dynamics in the Gobi Desert-riparian-oasis system of the lower Heihe River, a typical arid inland river basin located in northwestern China. The groundwater level and temperature were monitored in 14 shallow wells at 30 minutes intervals during the 2010–2012 period. After combining this information with meteorological and hydrological data, a comprehensive analysis was conducted to understand the dynamic behaviour of the shallow groundwater system and to determine the dominant factors that control the groundwater flow and processes. The results of the study indicate notably large temporal and spatial variations in both the groundwater level and temperature. Noticeable fluctuations in the groundwater level (0.5–1 m) and temperature (4–8°C) were observed in the riparian zone, evidencing a clear river influence. In comparison, the groundwater fluctuations in the Gobi Desert were more stable (the annual variations of the water table were less than 0.5 m, and the water temperature varied by no more than 2°C). Strong variations in the groundwater table (1.5–5.0 m/yr) and temperature (1.5–6.5°C), mainly caused by surface flood irrigation and groundwater pumping, were observed in the oasis area. The investigated sites were categorised into three typologies that reflect the dominant hydrological processes: (1) the riparian zone, dominated by riverbank filtration and groundwater evapotranspiration; (2) the Gobi Desert area, controlled by groundwater evaporation and lateral recharge; and (3) the oasis area, dominated by groundwater evapotranspiration as well as surface-groundwater interactions caused by human activities. Copyright © 2012 John Wiley & Sons, Ltd.