Abstract
Flooding’s impact on shallow groundwater is not well investigated. In this study, we analyzed changes in the depth and quality of a regional shallow aquifer in the 10.9 × 104 km2 Sanjiang Plain, Northeast China, following a large flood in the summer of 2013. Pre- (2008–2012) and post-flood records on groundwater table depth and groundwater chemistry were gathered from 20 wells across the region. Spatial variability of groundwater recharge after the flood was assessed and the changes in groundwater quality in the post-flood period were determined. The study found a considerable increase in the groundwater table after the 2013 summer flood across the region, with the largest (3.20 m) and fastest (0.80 m·s−1) rising height occurring in western Sanjiang Plain. The rising height and velocity gradually declined from the west to the east of the plain. For the entire region, we estimated an average recharge height of 1.24 m for the four flood months (June to September) of 2013. Furthermore, we found that the extreme flood reduced nitrate (NO3−) and chloride (Cl−) concentrations and electrical conductivity (EC) in shallow groundwater in the areas that were close to rivers, but increased NO3− and Cl− concentrations and EC in the areas that were under intensive agricultural practices. As the region’s groundwater storage and quality have been declining due to the rapidly increasing rice cultivation, this study shows that floods should be managed as water resources to ease the local water shortage as well as shallow groundwater pollution.
Highlights
Floods and their impact on waterways, society, and the economy have been investigated intensively worldwide
Chloride (Cl−) concentrations and electrical conductivity (EC) in shallow groundwater in the areas that were close to rivers, but increased NO3− and Cl− concentrations and EC in the areas that were under intensive agricultural practices
The flood’s effect on groundwater recharging in the eastern Sanjiang Plain appeared to be less direct than in the western Sanjiang Plain. These results suggest that future water resource management for the western Sanjiang Plain should especially consider practices for flood attenuation
Summary
Floods and their impact on waterways, society, and the economy have been investigated intensively worldwide. Floods are often hazardous to human life and the environment (e.g., soil erosion, inundation of lands, and swamping caused by the groundwater level rising) [1,2,3,4], they can be one of the main recharge sources for groundwater in some regions, especially for shallow groundwater [5,6] This aspect has not been addressed sufficiently in the research, probably due to the difficulty of quantifying flood impacts because of the characteristics of rapid occurrence, short-term duration of floods, and limitation in modeling the interchange processes and measuring the interchange processes [4]. Understanding how a flood impacts on the depth and quality of shallow groundwater can be relevant for regional water resources management planning and groundwater flooding risk management [7]
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