Assessing the Vulnerability of a Deltaic Environment due to Climate Change Impact on Surface and Coastal Waters: The Case of Nestos River (Greece)

In deltaic areas, riverine and coastal waters interact; hence, these highly dynamic environments are particularly sensitive to climate change. This adds to existing anthropogenic pressures from irrigated agriculture, industrial infrastructure, urbanization, and touristic activities. The paper investigates the estimated future variations in the dynamics of surface and coastal water resources at a Mediterranean deltaic environment for the twenty-first century. Therefore, an Integrated Deltaic Risk Index (IDRI) is proposed as a vulnerability assessment tool to identify climate change impact (CCI) on the study area. For this purpose, three regional climate models (RCM) are used with representative concentration pathways (RCPs) 4.5 and 8.5 for short-term (2021–2050) and long-term (2071–2100) future periods. Extensive numerical modeling of river hydrology, storm surges, coastal inundation, water scarcity, and heat stress on irrigated agriculture is combined with available atmospheric data to estimate CCI on the Nestos river delta (Greece). The IDRI integrates modeling results about (i) freshwater availability covering agricultural demands for three water consumption scenarios, i.e., a reference (REF), a climate change (CC), and an extended irrigation (EXT) scenario, combining river discharges and hydropower dam operation; (ii) inundated coastal areas due to storm surges; and (iii) heat stress on cultivated crops. Sustainable practices on irrigated agriculture and established river basin management plans are also considered for the water demands under combinatory scenarios. The differentiations of model outputs driven by various RCM/RCP combinations are investigated. Increased deltaic vulnerability is found under the RCP8.5 scenario especially for the long-term future period. The projected IDRI demonstrates the need for integrated water resources management when compared with risk indexing of individual water processes in the study area.