Abstract
The spatial patterns of lacustrine groundwater discharge (LGD) and associated nutrients input is crucial for effective management and protection of lakes. Multiple factors have been found to influence the spatial differences in LGD rates and associated nutrients loads, but the influence of geological conditions on the differences have not been well understood. In this study, we quantified LGD rates and associated nutrients loads in two sides with contrasting geological conditions of East Dongting Lake (EDL) within central Yangtze catchment and discuss the influence of geology on the spatial differences, through 222Rn mass-balance model, water chemistry coupled with existing geological data. The results showed that LGD rates were 38.66 ± 21.07 mm d−1 in the east EDL which is characterized by hilly geomorphy, deep/fast/narrow flowing, coarse-grained lakebed and large hydraulic gradients (0.004–0.006). Surprisingly, LGD rates were higher (92.82 ± 51.98 mm d−1) in the west EDL which is characterized by alluvial-lacustrine plain geomorphology, shallow/sluggish flowing, clayey or silty lakebed and low hydraulic gradients (0.0002–0.0015). The remaining factor determining the higher LGD rates in the west EDL is the permeability of the porous aquifer connected with the lake, which could be enlarged by some preferential pathways including large-scale buried paleo-channel and small-scale plant roots. The groundwater around the east EDL existed in a less confined environment, and frequent flushing led to low concentrations of nutrients. On the contrast, rapid burial of sediments and deposition of paleo-lake sediments since Last Deglaciation formed an organic-rich and reducing environment, which facilitated the enrichment of geogenic nutrients. As a result, the loads of LGD-derived nutrients in the west generally exceeded that in the east by one order of magnitude. In practice, future water resource management and ecological protection of Dongting Lake should focus on groundwater discharge in west EDL. This study highlights an important role of geological conditions in determining contrasting LGD rates and associated nutrients loads in large freshwater lakes.
Highlights
Recent studies have shown that groundwater is an important component of lake water (Kong et al., 2019; Kidmose et al, 2013; Stets et al, 2010; Schmidt et al, 2009; Roy and Hayashi., 2008) and lake chemistry (Kazmierczak et al, 2020; Kong et al, 2019; Luo et al, 2018; Burnett et al, 2017; Meinikmann et al, 2015) globally
21.07 mm d-1 in the east East Dongting Lake (EDL) which is characterized by hilly geomorphy, deep/fast/narrow flowing, coarse-grained lakebed and large hydraulic gradients (0.004 - 0.006)
The groundwater around the east EDL existed in a less confined environment, and frequent flushing led to low concentrations of nutrients
Summary
Recent studies have shown that groundwater is an important component of lake water (Kong et al., 2019; Kidmose et al, 2013; Stets et al, 2010; Schmidt et al, 2009; Roy and Hayashi., 2008) and lake chemistry (Kazmierczak et al, 2020; Kong et al, 2019; Luo et al, 2018; Burnett et al, 2017; Meinikmann et al, 2015) globally. LGD and LGD-derived nutrients can result in a deterioration of lake water quality and phytoplankton blooms (Holman et al, 2008; Krest et al., 2000), negatively effecting the aquatic ecosystem of a lake. There is an urgent need for the quantification of the contributions of LGD to lake water and nutrients balances, thereby providing a new perspective on lake water resources management and aquatic ecosystem protection. LGD and associated nutrients input are often characterized by large spatial variability due to the heterogeneity of geomorphy, surface hydrology, lakebed sediment lithology, hydrogeology, nutrient concentration levels of groundwater around lakes, etc (Wallace et al, 2020; Tecklenburg and Blume, 2017; Hare et al, 2017; Rosenberry et al, 2015; Meinikmann et al, 2015, 2013; Blume et al, 2013; Schneider et al, 2005).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
