Water Crisis of Lake Taihu, China Guangwei Zhu Taihu Laboratory for Lake Ecosystem Research (TLLER) Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences (NIGLAS) FEW Workshop: Food, Energy, and Water Nexus in Sustainable Cities

ACKNOWLEDGEMENTS Contract No. 2015DFG91980 Contract No. 2012ZX

Taihu Laboratory for Lake Ecosystem Research(TLLER) 中国科学院南京地理与湖泊研究所太湖湖泊生态系统研究站 Main campus is 110km west of Shanghai Hongqiao airport

Taihu Laboratory for Lake Ecosystem Research(TLLER) 中国科学院南京地理与湖泊研究所太湖湖泊生态系统研究站

Taihu Laboratory for Lake Ecosystem Research(TLLER) 中国科学院南京地理与湖泊研究所太湖湖泊生态系统研究站

Lake in China and where is Lake Taihu? Ma et al., Geophysical Research Letters, Taihu 2009 data 2693 lakes (> 1 km 2 ) km 2 (smaller than Superior) 243 disappeared In recent 40 years 13% shrink by size Lakes in China and the location of Taihu

Catchment of Taihu, megacity of Changjiang Delta Population density: >1200 Water surface: 2338 km 2 Average depth: 2 m Maximal depth: 3 m A big plate! Catchment: km 2 Wuxi Suzhou Shanghai Jiaxing Hangzhou Huzhou Changzhou Zhenjiang

Taihu is Water source of Wuxi, Suzhou and Shanghai Water intakes for water plants in Taihu.

Cyanobacterial blooms in Taihu

1950’s1970’s History of blooms in Taihu

Major player: Microcystis spp. Microcystis spp. in Taihu Microcystis aeruginosaMicrocystis wesenbergiiMicrocystis flos-aquae Photos by Gregory Boyer, at May

Supporting actor: Anabaena spp. Photos by Gregory Boyer, at May

Microcystis and Anabaena are Toxic produced species Su et al., Toxins, 2015 Microcystin

Water crisis caused by black patch in Taihu Water crisis happened at Wuxi during May 29 – 3 Jun 2007, for the block of intake at Gonghu blocked by black patch.

The cause 1: Extreme serious bloom, black patch Serious bloom start 8 April, a month earlier than normal.

The cause 2: Extreme warmer spring Spring Water temperature Spring Air temperature Qin et al, 2010

The cause 3: Suitable wind direction

3. Actions after water crisis of 2007

Catchment: In lake:Bloom collectionSediment dredgingEcological engineering Fertilization controlEcological restoration Water hyacinth The total investigation is over 100 billions RMB

What we done: Monitor and forecast the bloom

Based on Remote sensing image interpret bloom Chlorophyll aTemperatureSuspended solid Transparency Data sources: HJ – CCD MODIS MERIS GOCI Interpret model: APPLE model or 3 wavelengths model: nm; nm; > 730nm

And high frequency sensors buoy system monitor 水环境自动监测站点分类 EMB01EMB02EMB03 EMB08EMB10EMB11EMB12EMB13 EMB14 EMB4EMB5EMB6EMB7

Hydrodynamical bloom simulation model 3D model Model result Field data Model calcultion Model calibration Model development and calibration Stereo-monitoring system inLake Taihu Chlorophyll a and DO model Chl-a DO

3-days forecast report to local goverment

Possible reaction of local managers Water plants: Change the intake site, or use Yangtze river as source, prepare the active carbon addition. Tourism agency: Change the travel lines. Monitoring agency: Pay more attention to High possible zone. Bloom emergency action organization: adjust the collection power invest.

Other solution: reservoirs

Reservoir Qiandaohu: Surface area of 571 km 2, and volume of 18 billion m 3, 4 times of Taihu Invested 1 billion to protect water quality in recent 5 years. Will supply Hangzhou, one of the big cities in Changjiang Delta soon.

Take home messages Taihu, located in the center of megacity Changjiang Delta region, is seriously over-burden to supply the cities around it, largely affect the sustainable development of these cities. Environmental sensors and information technology, include high- frequency buoy and models, has been used to prevent drink water pollution event in Taihu. The ability of environmental technology to is limited. The over burden water issue is a social and economic issue, too. To solve the problem, more social and economic solutions should be involve in.

Thank you for your attention! Guangwei Zhu, professor Executive vice director of TLLER