Preprints
https://doi.org/10.5194/hess-2021-364
https://doi.org/10.5194/hess-2021-364

  07 Sep 2021

07 Sep 2021

Review status: this preprint is currently under review for the journal HESS.

Contrasting lacustrine groundwater discharge and associated nutrient loads in different geological conditions

Xiaoliang Sun1, Yao Du1,2, Yamin Deng1,2, Hongchen Fan1,2, and Teng Ma1,2 Xiaoliang Sun et al.
  • 1Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
  • 2State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430078, China

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.

Xiaoliang Sun et al.

Status: open (until 02 Nov 2021)

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Xiaoliang Sun et al.

Xiaoliang Sun et al.

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Short summary
Base on the 222Rn mass-balance model, the LGD rate and the loads of LGD-derived nutrients in the west was significantly larger than in the east. The factor determining the higher LGD rates is the permeability of the porous aquifer connected with the lake, which could be enlarged by some preferential pathways. The groundwater around the west EDL is enriched in geogenic nutrients, which further results in that the loads of LGD-derived nutrients generally exceeded.