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

water Article Hydrological Drought in Dongting Lake Area (China) after the Running of Three Gorges Dam and a Possible Solution Yizhuang Liu 1,2,3, Shu-Qing Yang 4 , Changbo Jiang 1,2,3,*, Yuannan Long 1,2,3 , Bin Deng 1,2,3 and Shixiong Yan 1 1 School of Hydraulic Engineering, Changsha University of Science & Technology, Changsha 410114, China; [email protected] (Y.L.); [email protected] (Y.L.); [email protected] (B.D.); [email protected] (S.Y.) 2 Key Laboratory of Dongting Lake Aquatic Eco-Environmental Control and Restoration of Hunan Province, Changsha 410114, China 3 Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province, Changsha 410114, China 4 School of Civil, Mining and Environmental Engineering, University of Wollongong, Wollongong 2522, Australia; [email protected] * Correspondence: [email protected]; Tel.: +86-0731-8525-8437 Received: 24 August 2020; Accepted: 25 September 2020; Published: 28 September 2020 Abstract: 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. Keywords: hydrological drought; water shortage crisis; Dongting Lake; water supply; dry season 1. Introduction Lakes play an important role in the water supply for agricultural, industrial, commercial, and residential use. However, the extreme hydrological drought event happens more frequently in the lake area due to climate change and human activities in recent years [1]. The hydrological drought has attracted increasing worldwide attention for the ever-increasing demand on freshwater sources due to population growth, urbanization and industrialization. Climate change often results in effects such as higher evaporation, lower precipitation, and higher temperature, which would exacerbate the drought severity [2,3]. Meanwhile, numerous studies have shown that human activities (e.g., dam construction, river dredging, and sand mining, etc.) would decrease the inflow to the lake directly or accelerate the water flow out of the lake [4–8]. For example, the impoundment of the upstream dam leads to an overall Water 2020, 12, 2713; doi:10.3390/w12102713 www.mdpi.com/journal/water Water 2020, 12, x FOR PEER REVIEW 2 of 14 accelerate the water flow out of the lake [4–8]. For example, the impoundment of the upstream dam leadsWater to an2020 overall, 12, 2713 reduction of the downstream water level, especially during the dry season;2 of 14 thus, the hydrological drought in the downstream-linked lakes is intensified [5,9,10]. reductionDongting ofLake, the downstream the second-largest water level, freshwater especially lake during in China, the dry is season; located thus, in the the middle hydrological reach of Yangtzedrought River. in the Its downstream-linked hydrological cycle lakes has is intensifiedbeen changed [5,9,10 significantly]. by the Three Gorges Dam [1,5,11–13]Dongting as its inflow Lake, theto second-largestthe lake has been freshwater reduced lake in in dry China, periods, is located especially in the middle from reachSeptember– of DecemberYangtze in River. the recent Its hydrological decades. cycle Consequently, has been changed its water significantly level byand the water Three Gorgessurface Dam areas [1,5 ,have11–13 ]been reducedas its significantly, inflow to the lake which has beenis caused reduced by in the dry TGD periods, after especially 2003 [12]. from More September–December specifically, thein statistics the recent decades. Consequently, its water level and water surface areas have been reduced significantly, show that, when compared with the pre-TGD period, the starting date of the dry season occurs earlier which is caused by the TGD after 2003 [12]. More specifically, the statistics show that, when compared and the duration of the dry season lasts longer after TGD’s operation in 2003 [8,14–16]. For example, with the pre-TGD period, the starting date of the dry season occurs earlier and the duration of the Dongtingdry season Lake has lasts experienced longer after TGD’sextreme operation drought in events 2003 [ 8in,14 2006–16]. and For 2011 example, with Dongtingthe water Lake surface has area 2 of aboutexperienced 350 km extreme (i.e., 1/8 drought of the eventssurface in area 2006 of and Dongting 2011 with Lake the water in the surface wet season) area of aboutin the 350 dry km season2 [17]. (i.e.,Moreover, 1/8 of the in surface 2011, areaextremely of Dongting low Lakewater in level the wet pe season)riod lasted in the dry80 days season in [ 17the]. Moreover,Dongting in Lake 2011, area and hundredsextremely lowof thousands water level periodof residents lasted 80suffered days in the the water Dongting shortage Lake area problem and hundreds [17]. of thousands ofPrevious residents studies suffered mainly the water focus shortage on problemthe identification [17]. and characteristics of the hydrological drought Previousas well as studies the mainlyfactors focusthat oninduce the identification the extreme and drought characteristics event of in the the hydrological Dongting drought Lake area [1,8,9,14–16].as well as Few the factors studies that investigate induce the extremehow to droughtenhance event the water in the Dongtingsupply of Lake Dongting area [1, 8Lake,9,14– 16[18,19].]. Actually,Few studies apart from investigate the environmental how to enhance change the water (e.g., supply climate of Dongting change Lake and [ 18human,19]. Actually, activities), apart one from of the the environmental change (e.g., climate change and human activities), one of the main reasons for the main reasons for the water shortage problem in the Dongting Lake area is that the lake cannot contain water shortage problem in the Dongting Lake area is that the lake cannot contain its floodwater till the its floodwater till the dry period since it is connected with Yangtze River directly, as shown in Figure dry period since it is connected with Yangtze River directly, as shown in Figure1. Therefore, to solve 1. Therefore,its water shortageto solve problem, its water one shortage has to convert proble itsm, floodwater one has into to waterconvert resources its floodwater in the dry into period. water resourcesYang etin al. the [20 dry] and period. Liu et Yang al. [21 ]et proposed al. [20] and an innovative Liu et al. flood[21] proposed control scheme an innovative (IFCS) as shownflood control in schemeFigure (IFCS)1. Together as shown with in the Figure existing 1. dike Together surrounding with thethe lake,existing they suggestdike surrounding building an innerthe lake, dike they suggestwith building several gates an inner to form dike an innerwith lakeseveral for mitigationgates to form of flood an inner disaster lake in wet for seasons.mitigation At theof flood beginning disaster in wetof wetseasons. seasons, At the lakebeginning water is of lowered wet seasons, to its dead the water lake level.water Duringis lowered the flood to its period, dead thewater peak level. Duringfloodwater the flood could period, be diverted the peak into floodwater the inner lake could for storage be diverted by opening into the the gates, inner thus lake the for inner storage lake by openingfunctions the gates, as a giant thus flood-detentionthe inner lake pond.functions More as details a giant could flood-detention be found in thepond. previous More study details [21 could]. be foundThe stored in the water previous will be study released [21]. when The the stored gates wa areter open will to regulatebe released the outflowwhen the in the gates dry are seasons. open to Therefore, a huge amount of floodwater stored in the inner lake can be converted to water resources in regulate the outflow in the dry seasons. Therefore, a huge amount of floodwater stored in the inner dry seasons. lake can be converted to water resources in dry seasons. FigureFigure 1. 1.TheThe schematic schematic of of the the IFCS inin Dongting Dongting Lake. Lake. In this paper, the effect of TGD on the hydrological drought was analyzed using 35 years (1981–2016) ofIn hydrologicalthis paper, the data effect observed of TGD at Chenglingji on the hydrological station, which drought is the typical was analyzed station to representusing 35 theyears water (1981– 2016)level of hydrological in Dongting Lake data [8 observed]. The feasibility at Chenglingji of applying station, the IFCS which to increase is the the typical usable station water storage to represent of the waterDongting level Lake in Dongting was examined Lake using [8]. The the hydrodynamic feasibility of applying module of the Mike IFCS 21.

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