Lake Tai Basin, China
In February 2012, eWater CRC completed work on the Lake Tai Water Pollution Treatment Project.
Under a joint Australian China Environmental Development Partnership (ACEDP) project, the eWater Source modelling system was applied to model water quantity and quality for a pilot area on the Dongshan Peninsula in the Lake Tai Basin.
About the Basin
Lake Tai is the third largest freshwater lake in China, bordering Jiangsu and Zhejiang provinces, providing water to 30 million residents and covering an area of 2,338 km2.
Rapid industrial and agricultural development in the last 20 years have caused water eutrophication in Lake Taihu watershed to become one of most serious environmental issues in Southeast China.
A severe algal bloom in the Lake in 2007 led to the development of the Lake Tai Master Plan (NDRC 2008), launched by the National Development and Reform Commission (NDRC), to improve nutrient management in the basin.
Under the ACEDP a joint project team was formed for the Lake Tai Water Pollution Treatment Project. The Project’s objective was to strengthen management and policy approaches in the Lake Tai basin by increasing awareness of Integrated River Basin Management (IRBM) and science-based management approaches and identify priority areas for further assistance.
eWater's aims for the project were to: a) build capacity in the use of the Source modelling system; b) apply the model to a small pilot area; and c) investigate strategies to improve nutrient (total nitrogen and total phosphorus) management in the Lake Tai Basin.
Source was applied to the 7.7 km2 (116,055 Mu) Dongshan Peninsula. The model consisted of 50 subcatchments with seven major landuse categories including aquaculture(46%), upland and lowland fruit trees (31%), low and high density urban (11%), vegetables (6%) and industrial (2%). The daily timestep model was run for the period 2001 to 2010.
The flexible nature of the Source software enabled a number of novel approaches to be integrated into the model. For example, the 3.8 km2 of aquaculture ponds on the Peninsula, were aggregated into 20 larger ponds and configured to simulate the filling and draining cycles of the aquaculture ponds on a daily basis.
The limited local data available to parameterise and calibrate the model was augmented with local knowledge and consultation, expert opinion from the Chinese and Australian technical working group and literature, to build and apply Source to the Dongshan Peninsula. Three future scenarios were investigated: (a) the removal of all septic systems from the low density urban areas and piping of STP outflow to main network (b) improved management of aquaculture, vegetables and upland fruit trees and (c) implementation of a major wetland to filter runoff from the aquaculture ponds.
Source model construction
A land use map was developed for the Dongshan Peninsula from local maps, local knowledge and Google satellite imagery (figure 1). The Source water modelling system was used to generate subcatchments for the upland areas (figure 2). For the lowland areas, subcatchments were drawn manually based on the land use map, location of the aquaculture pond clusters and canals and streams. The two models were combined to produce a single subcatchment map (figure 3).
A project technical working group was established comprised of Australian experts from eWater Cooperative Research Centre (eWater) and Earth Systems, along with Chinese officials and scientists from Suzhou Municipality, the Taihu Basin Authority (TBA) and the Nanjing Institute of Geography and Limnology (NIGLAS).
A series of workshops and training activities were conducted in China and Australia to build capacity for the development and use of the eWater Source framework.
A substantial amount of training material was translated into Chinese. Two site visits were then undertaken to assist in developing and modifying the base model for the Dongshan Peninsula and to develop scenarios based on proposed nutrient management strategies. Over 40 Chinese and English papers were sourced and reviewed in the collation of model input parameters.
Local water and agricultural managers and farmers from within the Peninsula were also consulted to obtain flow and water quality data and advice on agricultural practices, for example, current practices and operations of aquaculture ponds.
The management of Lake Tai Basin is a challenge that requires long-term commitment. Significant gains have been achieved to date. The Lake Tai Master Plan provides a solid basis and broad scale assessment of the relative contributions of pollutant sources to Lake Tai, both spatially and by industry. This modelling exercise supported the planning process. It demonstrated how Source could be used to explore pollutant generation sources and the relative changes in nutrient inputs to the Lake resulting from alternative management strategies at a finer scale. The flexibility of the Source, in allowing a variety of sub-models to be chosen and particularly in allowing addition of ‘expressions’, was useful in developing a model rapidly.
A number of challenges were identified through the project including the inability to access base data layers such as topographic data and landuse. The lack of runoff and water quality data prevented comprehensive calibration and validation of the model. Despite these challenges, the modelling exercise has improved our understanding of the Dongshan Peninsula, allowed key data gaps to be identified and enabled a range of management options to be explored.
- Academy of Environmental Science, Suzhou Environment Institute
Earth Systems, Australia
- Earth Systems, China
- Department of Primary Industries, Victoria, Australia
Lake Tai Basin Authority
- Nanjing Institute of Geography and Limnology Science, China