Study on Synergistic Mechanism of Water Environment Governance in Dongting Lake Basin Based on Evolutionary Game

Watershed water environment governance has always been a research hotspot in the field of transboundary governance. Based on evolutionary game theory, the regional governments of East Dongting Lake, West Dongting Lake and South Dongting Lake were taken as participants to construct a tripartite game model, and the game evolution strategies under unconstrained and constrained conditions were explored respectively, so as to analyze the influencing factors of the construction of synergistic mechanism of water environment governance in Dongting Lake Basin. The results show that: (1) Under the unconstrained condition, the stable strategy of the evolutionary game is “two parties govern, one party does not govern”. However, without intervention of external restraint measures for a long time, the players keep learning and improving according to the game results, and the final synergy mechanism cannot be achieved. (2) Under constraint conditions, the composition of synergistic mechanism mainly depends on the size of ecological compensation and punishment given by the superior government and the duration of constraint by the superior government.

Hydrological Drought in Dongting Lake Area (China) after the Running of Three Gorges Dam and a Possible Solution

Dongting Lake is located at the downstream of Three Gorges Dam (TGD) and the hydrological drought is intensified after the impoundment of TGD as the dry period has been extended from 123 days/year before the operation of TGD (1981–2002) to 141 days/year (2003–2016) on average. Particularly, the Dongting Lake’s water shortage becomes very severe. To solve the problem caused by upstream dams, an innovative flood control scheme (IFCS) was introduced, and its feasibility of application in Dongting Lake is studied using the hydrodynamic module of Mike 21. The results show the IFCS can effectively convert the peak discharge of floodwater in wet seasons into water resources in dry seasons as the IFCS could significantly increase the usable water storage of the lake. For example, the usable water storage could increase to 2.85 billion m3 and 1.81 billion m3 in the extreme drought year of 2006 and 2011, respectively. The average increment of the water level would be about 0.4 m, 0.6 m, and 0.5 m in the West Dongting Lake (WDL), South Dongting Lake (SDL), and the East Dongting Lake (EDL), respectively, if the water stored in the inner lake was discharged uniformly in 30 days (27 November to 27 December 2006) with the application of IFCS. This study may provide an innovative method to alleviate the water shortage problem in Dongting Lake and other similar lakes.

Microplastics in Sediment and Surface Water of West Dongting Lake and South Dongting Lake: Abundance, Source and Composition

Microplastic pollution was investigated in sediment and surface water in West Dongting Lake and South Dongting Lake for the first time. The abundance of microplastics ranged from 616.67 to 2216.67 items/m3 and 716.67 to 2316.67 items/m3 in the lakeshore surface water of West Dongting Lake and South Dongting Lake, respectively. The highest levels of microplastic pollution were found in the lakes’ outlets. In the lake center sites of the West Dongting Lake and South Dongting Lake, the abundance of microplastics ranged from 433.33 to 1500 items/m3 and 366.67 to 1566.67 items/m3, respectively. Meanwhile, the study found that in lakeshore sediment of West Dongting Lake and South Dongting Lake, microplastic concentrations ranged from 320 to 480 items/m3 and 200–1150 items/m3. Polystyrene (PS) and polyethylene terephthalate (PET) were most common in the surface water and sediment samples, respectively. In addition, we suggest that the effects of polymer types in microplastics should be taken into account when considering abundance. This study can provide valuable points of reference to better understanding microplastic pollution in inland freshwater areas.