Water Allocation underFuture Climate Change and Socio-Economic Development
The Case of PearlRiver Basin,
Wageningen University, Wageningen, the Netherlands (2017)
With references, withsummary in English
Water shortage has become a majorchallenge in many parts of the world due toclimate change and socio-economic development. Allocating water is critical to meethuman and ecosystem needs in these regions now and in the future. However,water allocation is being challenged by uncertainties associated with climatechange and socio-economic development. This thesis aims to assess the combinedeffects of climate change and socio-economic development on water supply anddemand in the Pearl River Basin (PRB) in China, and identify water allocationplans, which are robust to future climate change and socio-economicdevelopment.To do so,the impact of climatechange on future water availability is first assessed. Next, different modelframeworksare developed to identify robust water allocationplansforimproving reservoir management, ensuring sufficient flow into the delta toreduce salt intrusion, and providing sufficient freshwater for human andindustrial consumptionunder future climate change and socio-economicdevelopment.
Results show thatwater availability is becoming more variable throughout the basin due toclimate change. River discharge in the dry season is projected to decreasethroughout the basin. For a moderate climate change scenario (RCP4.5), lowflows reduce between 6 and 48 % depending on locations. For a high climatechange scenario (RCP8.5), the decreases of low flows can reach up to 72%. Inthe wet season, river discharge tends to increase in the middle and lowerreaches and decreases in the upper reach of the Pearl River Basin. Thevariation of river discharge is likely to aggravate water stress. Especiallythe reduction of low flow is problematic as already the basin experiences watershortages during the dry seasonin the delta.
The model frameworksdeveloped in this study not only evaluate the performance of existing waterallocation plans in the past, but also the impact of future climate change onrobustness of previous and newly generated water allocation plans. Theperformance of the four existing water allocation plans reduces under climatechange.New water allocation plans generated by the two model frameworks performmuch better than the existing plans.Optimising water allocation using carefully selected state-of-the-artmulti-objective evolutionary algorithms in the Pearl River Basin can help limitwater shortage and salt intrusion in the delta region. However, the currentwater allocation system with six key reservoirs is insufficient in maintainingthe required minimum discharge at two selected gauge stations under futureclimate change. More reservoirs, especially in the middle and lower reaches ofthe Pearl River, could potentially improve the future low flow into the delta.
This study alsoexploredfuture water shortage in the Pearl River Basinunder different water availability and water use scenarios. Four different strategies to allocate water were defined. These waterallocation strategies prioritize upstream water use, Pearl River Delta wateruse, irrigation water use, and manufacturing water use, respectively.Results show that almost all the regionsin the Pearl River Basin are likely to face temporary water shortage under thefour strategies.The increasing water demand contributes twiceas much as the decreasing water availability to water shortage.Allfour water allocation strategies are insufficient to solve the water scarcityin the Pearl River Basin. The economic losses differ greatly under the fourwater allocation strategies. Prioritizing the delta region or manufacturingproduction would result in lower economic losses than the other two strategies.However, all of them are rather extreme strategies. Development of waterresources management strategies requires a compromise between different waterusers. Optimization algorithms prove to be flexible and useful tool in adaptivewater resources allocation for providing multiple approximate Pareto solutions.In addition, new technologies and increasing water use efficiency will beimportant to deal with future water shortage in the Pearl River Basin.