Lin Zihan, Qi Jiaguo
Center for Global Change and Earth Observations, Michigan State University, East Lansing, MI 48823, USA.
Center for Global Change and Earth Observations, Michigan State University, East Lansing, MI 48823, USA; Institute of Islands and Coastal Ecosystems, Zhejiang University, Hangzhou, China.
Environ Res. 2017 Oct;158:24-32. doi: 10.1016/j.envres.2017.05.016. Epub 2017 Jun 6.
Recent proliferation of hydro-dams was one of the nature-based solutions to meet the increasing demand for energy and food in the Lower Mekong River Basin (LMRB). While construction of these hydro-dams generated some hydropower and facilitated expansion of irrigated lands, it also significantly altered the basin-wide hydrology and subsequently impacted wetland ecosystems. Unintended adverse consequences of ecosystem services from lakes and wetlands offset the intended gains in hydroelectricity and irrigated agriculture. The trade-offs between gains in energy and food production and losses in aquatic ecosystem services were perceived to be significant but knowledge of the magnitude, spatial extent, and type of ecosystem services change is lacking and, therefore, the question whether the hydro-dam is an optimized solution or a potential ecological problem remains unanswered. In this study, as the first step to answer this question and using the Tonlé Sap Lake as an example, we quantified one of the impacts of hydro-dams on lake ecosystem's phenology in terms of open water area, a critical ecological characteristic that affects lake systems' fish production, biodiversity, and livelihoods of the local communities. We used the MODIS-NDVI time series, forecast function and the Mann-Kendall trend test method to first quantify the open water area, analyzed its changes over time, and then performed correlation analysis with climate variables to disentangle dam impacts. The results showed reduced hydro-periods, diminishing lake seasonality and a declining trend in Tonlé Sap Lake open water area over the past 15 years. These changes were insignificantly related to climatic influence during the same period. It is concluded that basin-wide hydro-dam construction and associated agricultural irrigation were deemed to be the primary cause of these ecological changes. Further analyses of changes in the lake's ecosystem services, including provision and cultural services, need to be carried out in order to have a holistic understanding of the trade-offs brought by the hydro-dam proliferation as a solution to the emerging energy and food demand in the LMRB.
近期水坝的激增是满足湄公河下游流域（LMRB）不断增长的能源和粮食需求的基于自然的解决方案之一。虽然这些水坝的建设产生了一些水电并促进了灌溉土地的扩张，但它也显著改变了全流域的水文状况，进而影响了湿地生态系统。湖泊和湿地生态系统服务产生的意外负面影响抵消了水电和灌溉农业的预期收益。能源和粮食生产的收益与水生生态系统服务损失之间的权衡被认为是巨大的，但目前缺乏对生态系统服务变化的幅度、空间范围和类型的了解，因此，水坝是一个优化的解决方案还是一个潜在的生态问题，这个问题仍然没有答案。在本研究中，作为回答这个问题的第一步，并以洞里萨湖为例，我们从开阔水域面积的角度量化了水坝对湖泊生态系统物候的影响之一，开阔水域面积是一个关键的生态特征，影响着湖泊系统的鱼类产量、生物多样性和当地社区的生计。我们使用MODIS-NDVI时间序列、预测函数和曼-肯德尔趋势检验方法首先量化开阔水域面积，分析其随时间的变化，然后与气候变量进行相关性分析以厘清大坝的影响。结果显示，在过去15年里，洞里萨湖的水周期缩短，湖泊季节性减弱，开阔水域面积呈下降趋势。这些变化与同期的气候影响关系不显著。研究得出结论，全流域的水坝建设和相关的农业灌溉被认为是这些生态变化的主要原因。为了全面了解水坝激增作为应对湄公河下游流域新出现的能源和粮食需求的解决方案所带来的权衡，需要进一步分析湖泊生态系统服务的变化，包括供给服务和文化服务。
