National Institute of Education, Nanyang Technological University, Singapore.
National Institute of Education, Nanyang Technological University, Singapore; Asian School of the Environment, Nanyang Technological University, Singapore.
Sci Total Environ. 2021 Jul 10;777:146180. doi: 10.1016/j.scitotenv.2021.146180. Epub 2021 Mar 3.
This paper investigates the impacts of extensive riverbed mining in the Lower Mekong on the water level, extent and volume of the Tonlé Sap Lake, the largest freshwater lake in Southeast Asia. Our results indicate that the lake's volume has decreased from 1980 to 2018 (p-value = 0.016), with water levels at Phnom Penh Port and Phnom Penh Bassac showing decreasing trends since 1980 (p-values <0.0001). However, discharge at Phnom Penh Bassac (1960-2002) presented an insignificant trend (p-value = 0.147), indicating that riverbed incision due to extensive sand mining in Phnom Penh has affected the Mekong's water levels more than basin-scale climatic factors. Similarly, the modulation of a limited portion of water by upstream dams is unlikely to have caused dramatic inundation variation along the Lower Mekong River around Tonlé Sap. A hysteretic relationship between water levels at Prek Kdam and Tonlé Sap indicates that Tonlé Sap's water level is largely controlled by Tonlé Sap River and the Mekong, and declining water levels at Prek Kdam due to extensive sand mining in Phnom Penh is directly related to the shrinking of the lake. Although there are three main inflows into Tonlé Sap (from the Mekong, local tributaries and direct precipitation), the Mekong's contribution is the largest; tributary discharge and rainfall did not display any significant trend over the investigated period as well. Additionally, the analysis of high-resolution images revealed a recent intensification of riverbed mining, with Phnom Penh being a mining hotspot in the Lower Mekong. Considering its economic and ecological importance, the shrinking of Tonlé Sap would have grave repercussions for the region. Since sand demand is unlikely to weaken in the foreseeable future, these new insights can potentially help inform regulatory frameworks in ensuring sustainable sand extraction rates.
本文研究了湄公河下游大规模河床采砂对东南亚最大淡水湖洞里萨湖水位、面积和水量的影响。研究结果表明，自 1980 年以来，洞里萨湖的水量已经减少（p 值=0.016），金边港和金边巴萨克的水位呈下降趋势（p 值均<0.0001）。然而，1960 年至 2002 年期间，金边巴萨克的流量没有明显的趋势（p 值=0.147），这表明由于金边大规模采砂导致的河床下切对湄公河水位的影响大于流域尺度的气候因素。同样，上游大坝对有限水量的调节不太可能导致洞里萨湖周围湄公河下游的洪水变化显著。普雷克德姆和洞里萨湖水位之间的滞后关系表明，洞里萨湖的水位主要由洞里萨河和湄公河控制，由于金边的大规模采砂，普雷克德姆的水位下降与湖泊的缩小直接相关。尽管洞里萨湖有三个主要的入流（来自湄公河、当地支流和直接降水），但湄公河的贡献最大；支流流量和降雨量在研究期间也没有显示出任何显著的趋势。此外，对高分辨率图像的分析显示，最近河床采砂活动有所加剧，金边是湄公河下游的一个采砂热点。鉴于其经济和生态重要性，洞里萨湖的缩小将对该地区产生严重影响。由于在可预见的未来，对沙子的需求不太可能减弱，这些新的见解可以为确保可持续的采砂率的监管框架提供潜在的帮助。
