Integrated water resource management has become the main concern for both scientists and public after recognizing that river ecosystems are deteriorating due to heavy anthropogenic (i.e. originating from human activities) pressures and alterations on both hydrology and geomorphology. This issue has been addressed with the Water Framework Directive (WFD) by the terms ‘ecological status of water bodies’ and ‘quality elements for the classification of ecological status’. Among these quality elements, hydromorphological quality elements cover both hydrology and geomorphology of waterbodies. In this study, two main research questions are investigated:
1- What are the environmental flow requirements in Sakarya watershed?
2- What is the hydromorphological status of Sakarya watershed?
Environmental flows are the water requirements, not only in magnitude, but also in frequency, timing, rate of change and duration, for maintaining both health of river ecosystems and ecosystem services they provide to people. The ‘environmental flows’ term which is initially defined as ‘minimum flows’ have been evolved to more holistic concept where all components have to be defined, including floods to extremely low flows. In this study, both minimum and holistic environmental flow requirements of Sakarya River are calculated. Minimum flows were calculated using Wetted Perimeter, Flow Duration Curve Analysis, and Tennant (Montana) methods at 17 selected points, while as the holistic approach, all components of environmental flows are calculated using natural streamflow data at selected streamflow gages within the basin. Multivariate multiple linear regression models were developed for the natural streamflow estimation. For the hydromorphological assessment, Indicators of Hydrologic Alteration (IHA) – Range of Variability (RVA) methodology is implemented and hydromorphological pressures and alterations indicators are determined. Minimum environmental flow results validated the statement that one environmental flow value is not enough to maintain critical river functions and processes, such as river channel bed formation processes – erosion, aggradation, etc. however they can be used as a preliminary decision tool for environmental flow policies. Thus, a more holistic approach is implemented and the outcomes of this study will help both decision makers and future research studies by providing a detailed environmental flow assessment in Sakarya River based on both hydrologic and geomorphologic functioning. In addition to environmental flows, prioritization of hydromorphologically risky areas in the watershed will be defined using the results of alteration index scores and management actions will be suggested accordingly.
By: Cansu Özcan
Advisor: Assoc. Prof. Dr. Emre Alp
Date: 08.05.2019