DETECTING RISKS FOR TURKEY’S WETLAND SYSTEMS IN TERMS OF RIVER FLOWS AND ENVIRONMENTAL FLOW REQUIREMENTS

Ali Gul, Gulay Onusluel Gul, Aysegul Kuzucu

Dokuz Eylul University, Faculty of Engineering, Department of Civil Engineering, Izmir, Turkey

Abstract

Wetlands in Turkey, as a significant component of the protected areas network additionally containing national parks, nature protection areas, special protection areas (SPAs) and wild-life development areas, represent a very diverse set of ecosystems. They are, however, subject to considerable risks of biodiversity loss also arising from the changes in their hydrology as an expected consequence of the breaks in their natural water regimes, due to damming of rivers, the overuse of water upstream as well as hydrologic impacts of climate change. Maintaining the full spectrum of naturally occurring flows in a river is almost impossible in Turkey’s economically competing watersheds due to catchment landuse changes and accompanying water resources development. In this regard, environmental flow requirements, which generally refer to an ecologically acceptable flow regime designed to maintain a river in an agreed or predetermined ecological state, should represent a compromise between water resources development on one hand, and river ecology maintenance on the other. Quantifying this demand, however, is a difficult task due to the lack of both the understanding of, and quantitative data on, relationships between river flows and multiple components of river ecology. The major criteria for determining environmental requirements include the maintenance of flow variability. In the presented study, over 35 wetlands belonging to different ecological regions in Turkey are assessed together. The changes in the water regimes observed in the period 1960-2000 are considered together with concurrent ecological conditions (so-called environmental management classes). The desktop approach integrated into the Global Environmental Flow Computation (GEFC) software of the International Water Management Institute (IWMI) is implemented for all analyzed sites in several steps by considering, in the first step, a period-of-record flow duration curve (FDC), i.e. a cumulative probability distribution function of flows. Once such a curve is determined, it is possible to convert it into an environmental FDC for any present ecological condition and finally actual environmental monthly flow time series. The monthly series of environmental flows computed in this wise are further analyzed in the study for the set of selected wetlands in order to reflect the spatially varying risks on wetlands collectively arising from human intervention and changing climatic conditions. The results are presented in different forms of indicator-based risk maps and graphs to help correlate biodiversity loss in wetlands to the decrease in environmental flows in course of time.

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