Groundwater sources, flow patterns, and hydrochemistry of the Central Yinchuan Plain, China

Groundwater in the Yinchuan Plain (China) is a critical domestic resource that is also used for agricultural irrigation and to maintain ecological environments, among other purposes. Recent research has shown that ineffective planning of water resources, along with large-scale groundwater pumping (mining) has led to ecological problems. To further analyze the characteristics of the regional groundwater flow patterns, and guide the development and utilization of water resources, potentiometric, hydrochemical, and isotopic data were collected along a 60-km transect that crosses the middle Yinchuan Plain. The data were used to develop a two-dimensional conceptual model of the sources, flow patterns, and geochemical evolution of groundwater from the Helan Mountains in the west across the Yellow River in the east. An important component of the model is that in the process of groundwater flow from west to east, the flow direction changes due to the influence of a thick fine-grained sandy-clay unit and long-term groundwater pumping. Local lakes and the shallow groundwater system are recharged by water from the Yellow River. Geochemically, water within the proluvial deposits exhibits relatively low concentrations of total dissolved solids. Further east, the water gradually becomes brackish. The geochemical composition of the shallow groundwater beneath the fluviolacustrine plain west of the Yellow River is also controlled by evaporation, precipitation and cation exchange processes. In other areas, groundwater chemistry is mainly controlled by water–rock interactions and cation exchange. This study enhances understanding of groundwater flow in the region, and provides information critical to water resources development and management.