Insights into long-term changes of groundwater levels in the typical region of Zhangjiakou City, China.

Little information is available on the long-term changes of groundwater levels and their associated influencing factors. Zhangjiakou City was chosen as a case to reveal the temporal and spatial dynamics of groundwater level and its driving factors in the long term. Herein, the observation data of groundwater level from 56 wells was investigated from 1981 to 2015, including the collected meteorological data, socio-economic data, and groundwater resource exploitation situation. Results showed that the groundwater level in Zhangjiakou City tended to be decreased, and the decrease rate was gradually accelerated. In the past 35 years, the groundwater level of Bashang Plateau has decreased by 3.59 m < 3.6 m in Yuyang Basin < 7.17 m in Zhuohuai Basin < 20.41 m in Chaixuan Basin. The dynamic changes of groundwater level in four geomorphic units in Zhangjiakou City were significant correlation between the total population and other socio-economic factors, including primary industry production value; common cultivated land area; effective irrigation area; total grain yield; total vegetable yield; total production of pork, beef, and mutton; secondary industry production value; tertiary industry production value; and year-end total population. Furthermore, the principal component analysis of groundwater level variation in Zhangjiakou city showed that the variance contribution rates of the first principal component in the characteristic indicators of the Bashang Plateau, Chaixuan Basin, Zhuohuai Basin, and Yuyang Basin were 75.7%, 83.9%, 66.1%, and 77.8%, respectively, which mainly reflect the information of socio-economic factors. This indicated that socio-economic factors were the main driving factor influencing the continuous decline of groundwater levels in Zhangjiakou City. The obtained findings can provide new insights into the sustainable development of social economy and the rational utilization and allocation of regional water resources. [ABSTRACT FROM AUTHOR]