Assessing the impacts of climate change on the water resources of the Seyhan River Basin in Turkey: Use of dynamically downscaled data for hydrologic simulations

We explored the potential impacts of climate change on the hydrology and water resources of the Seyhan River Basin in Turkey. A dynamical downscaling method, referred to as the pseudo global warming method (PGWM), was used to connect the outputs of general circulation models (GCMs) and river basin hydrologic models. The GCMs used in this study were MRI-CGCM2 and CCSR/NIES/FRCGC-MIROC under the SRES A2 scenario, and the downscaled data covered two 10-year time slices corresponding to the present (1990s) and future (2070s). The hydrologic models along with a reservoir model were driven using the downscaled data for the present period. As a result, the temperature and precipitation, which were dynamically downscaled through bias-correction, were in good agreement with the observed data. The hydrologic simulation results also matched the observed flow, reservoir volume, and dam discharge. Therefore, we concluded that the PGWM combined with bias-correction is extremely useful to produce input data for hydrologic simulations. The simulation results for the future were compared with those for the present. The average annual temperature changes in the future relative to the present were projected to be +2.0°C and +2.7°C by MRI and CCSR, respectively. The annual precipitation decreased by 157mm (25%) in MRI-future and by 182mm (29%) in CCSR-future, and the annual evapotranspiration decreased by 36mm (9%) in MRI-future and by 39mm (10%) in CCSR-future; the annual runoff decreased by 118mm (52%) in MRI-future and by 139mm (61%) in CCSR-future. The analysis of water resource systems was conducted by using a simple scenario approach to take into account changes in water use. This analysis indicated that despite the impacts of climate change, water scarcity will not occur in the future if water demand does not increase. However, if the irrigated area is expanded in the future under the expectation of current flow, water scarcity will occur due to the combination of decreased inflow and increased water demand. Thus, in the Seyhan River Basin, water use and management will play more important roles than climate change in controlling future water resource conditions.