International Research Fellowship Program: Risk Analysis of a Near-Future Urban Water Crisis in Turkey's Mega-City, Istanbul from Natural Processes

[401836]“国际研究奖学金计划”使美国科学家和工程师能够到国外进行3至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Lisa Doner博士与Namik M. Cagatay博士在土耳其伊斯坦布尔马斯拉克的伊斯坦布尔技术大学进行为期22个月的研究。土耳其的伊斯坦布尔依靠两个沿海湖泊提供超过55%的饮用水：Terkos湖和Buyukcekmece湖。这两个湖都是自然形成的泻湖河口，被筑坝后变成了湖泊；1883年的Terkos和100多年后的1989年的Buyukcekmece。如果这两个湖中的任何一个失去淡水来源，伊斯坦布尔将立即面临严重的缺水问题，但这两个湖的地质特征都不稳定。这些盆地正在经历自然过程，在短期和长期的时间尺度上发挥作用，这限制了它们作为淡水湖的寿命。不幸的是，对于这些湖泊过去和现在的沉积速率、湖盆下的海洋地下水位深度，以及影响这两个地点的海啸（潮汐波）频率，人们几乎一无所知。该项目与伊斯坦布尔技术大学合作，正在审查通过自然（渐进和灾难性）过程失去这些淡水资源的风险。影响湖泊的渐进过程包括由于沉积物填充、藻类过度生长和盐水入侵而导致的湖泊容量和整体水质的损失。这些渐进过程是重要的短期风险，因为其他因素，如极端气候事件，可能与渐进变化结合并放大。本项目主要研究填充率及藻类生长对水质的影响。它还绘制了第一张现代湖泊深度和两个湖泊的咸水地下水位深度地图。如今，特尔科斯湖和布尤克梅克湖被水坝和屏障加固与海洋隔离开来。这些屏障是每个盆地完整性中最薄弱的环节，如果进一步削弱，很容易发生灾难性的崩塌。该项目正在研究屏障完整性的变化，使用覆盖过去30年的屏障宽度的卫星图像，并检查屏障两侧的沉积物沉积和侵蚀模式。另一个渐进的过程是斑马贻贝的入侵，斑马贻贝是里海（黑海东北部）的一种物种，已经开始出现在土耳其的湖泊中。到目前为止，它的传播记录很少。因此，在这个项目中，来自这些沿海湖泊的地表样本，以及马尔马拉海周围湖泊网络的常规采样策略，正在被用来创建一个基于gis的物种分布图系列，这可以用于管理和保护未受感染的流域。地震和/或海啸可能导致湖泊水的灾难性损失。土耳其地震活跃，未来几十年伊斯坦布尔附近发生强烈地震的可能性很高（60%）。除了地震对大坝和海洋屏障造成的破坏外，这些沿海泻湖还面临海啸的威胁。该项目通过表明淡水环境和咸水环境之间急剧转变的沉积物特征变化，以及大规模流域扰动的迹象，寻找过去与地震有关的事件的证据。

0401836DonerThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-two month research fellowship by Dr. Lisa Doner to work with Dr. Namik M. Cagatay at the Istanbul Technical University in Maslak, Istanbul, Turkey.Istanbul, Turkey relies on two coastal lakes for more than 55% of it's drinking water: Terkos Lake and Buyukcekmece Lake. Both of these lakes are naturally occurring lagoonal estuaries that were dammed and turned into water lakes; Terkos in 1883 and Buyukcekmece over 100 years later, in 1989. Istanbul would face an immediate and severe water shortage if either of these two lakes were lost as freshwater sources, yet neither lake is a geologically stable feature. The basins are undergoing natural processes, acting over short and long timescales, that limit their lifespan as freshwater lakes. Unfortunately, almost nothing is known about the lakes' past and present sedimentation rates, the depth of the marine water table beneath the lakes' basins, or the frequency of tsunami (tidal wave) affecting either site. This project, in partnership with Istanbul Technical University, is examining the risk of losing these freshwater resources through natural (gradual and catastrophic) processes. Gradual processes affecting the lakes include the loss of lake capacity and overall water quality due to sediment infilling, excessive algal growth, and saltwater intrusion. These gradual processes are important short-term risks because other factors, such as an extreme climate event, can combine with and amplify the progressive change. This project is studying the infilling rate and the affect of algal growth of water quality. It is also producing the first modern maps of lake depth and depth of the saltwater table for both lakes. Terkos and Buyukcekmece lakes are isolated from the sea today by dams and barrier reinforcements. These barriers are the weakest points in the integrity of each basin and are susceptible to catastrophic collapse if further weakened. The project is studying the change in barrier integrity, using satellite images of barrier width covering the last 30 years, and examining the pattern of sediment deposition and erosion on both sides of the barrier. Another gradual process is invasion of the zebra mussel, an species from the Caspian Sea (northeast of the Black Sea), which has started to appear in lakes in Turkey. The spread of it is poorly documented so far. So, in this project, surface samples from these coastal lakes, as well as a regular sampling strategy at a network of lakes around the Sea of Marmara, are being used to create a GIS-based distribution map-series for this species which could be used in management and protection of uninfected watersheds.Catastrophic loss of the lakes' water can result from earthquake and/or tsunami. Turkey is seismically active and there is a high (60%) probability of a strong earthquake near Istanbul for the next few decades. Aside from the damage to the dams and marine barrier caused by earthquake, these coastal lagoons face tsunami hazards. This project is looking at evidence of past seismic-related events, through changes in sediment characteristics that indicate a sharp transition between fresh and saltwater environments, and indications of massive watershed disturbance.