Groundwater level declines in Tianjin, North China: climatic variations and human activities.

The North China Plain faces increasing pressure on fresh water resources due to economic development and climate variations. The effects of climate variations and human activities on the groundwater system in Tianjin, Northern China, were analyzed using an autoregressive integrated moving average model. Our result showed that the groundwater dynamics were influenced by climatic factors and that human activities gradually played a dominant role in the increasing groundwater withdrawal. During the period of 1950–2010, there were no significant trends in annual and wet season precipitation based on Mann–Kendall tests at the 5% significance level. Surface air temperature significantly increased, but potential evapotranspiration and phreatic water evaporation were not significantly changed. The effect of precipitation on groundwater-level fluctuation was decreasing, and the groundwater level declines mainly resulted from the groundwater withdrawal in Tianjin. Sustainable management of groundwater resources in the North China Plain will largely hinge on sustainable management of groundwater withdrawal, especially the efficient use of water for agriculture production. [ABSTRACT FROM AUTHOR]