The 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.
