Changes in groundwater resources and their influencing factors in Songnen Plain, China

The Songnen Plain is a crucial agricultural area in China, and in the past 20 years, a large number of dry fields have been developed into paddy fields in order to improve land output efficiency. As a result, the effective irrigation area of agriculture has increased annually, and the conversion mode and quantity between surface water and groundwater have changed considerably. It is essential to identify the changes in groundwater resources and their influencing factors for the sustainable development of economy and society. This study evaluates groundwater resources in the Songnen Plain using the water balance method based on meteorological, hydrological and groundwater monitoring data from 2000 to 2020. The results show that the groundwater resources in the region amount to 15.945 billion m3 with precipitation infiltration being the most important component, accounting for 73.09%, which is followed surface water irrigation infiltration and river and ditch infiltration, constituting 14.55% and 10.32%, respectively. Different factors influence groundwater resources in different periods. Compared to 1985, the increase of surface water irrigation infiltration is the primary factor responsible for the increase of groundwater resources, while other recharge sources have decreased during the same period. Compared to 2005, all groundwater resources have increased, with the increase of surface water irrigation infiltration and river channel infiltration being the primary factors.