Simulation of the hydrological impacts of climate change on the Zayanderud River Basin and the implications for the Gavkhuni Ramsar wetland, Iran.

The hydrological characteristics of wetlands exert important ecological controls that influence the provision of many ecosystem services that wetlands provide. Wetlands are, however, subject to a host of pressures that include changes in their hydrology or the hydrology of the catchments in which they are located. Stressors include climate change, water withdrawals and diversions, as well as land-use change. Resulting alterations in wetland hydrological regime, which in some cases can occur relatively rapidly, outside the ecosystem's natural variability can have profound ecological consequences. Wetlands are, in particular, sensitive to changes in the quantity and timing of water inflows. This is especially true of floodplain and lacustrine wetlands located in the lower reaches of river systems. Assessment of the impacts of these changes and the development of strategies for sustainable wetland management, conservation, and restoration requires the application of numerical models that can accurately represent the hydrological conditions within wetlands and their catchments. High resolution, physically-based models provide a means of representing the often complex interactions between biophysical characteristics and hydrological processes. This study is based on the development of a MIKE SHE / MIKE 11 model of Zayanderud River Basin, which ultimately discharges into the Gavkhuni wetland, a brackish, shallow, lake and one of Iran's Ramsar sites. The wetland is the subject of local and national concern given the drought conditions that have persisted, with inflows from the Zayanderud River being eliminated in recent years. The MIKE SHE model employs a wide range of data obtained from national and global datasets whilst a number of approaches are used to address the significant gaps that characterize meteorological datasets for the river basin. The model also includes irrigation abstractions that are implicated in the decline of the Gavkhuni wetland. Following calibration/validation against observed river discharge at nine stations, the model is used to undertake a preliminary investigation of the impacts of climate change, with a particular emphasis on inflows to the Gavkhuni wetland, using an ensemble of GCMs.