Abstract

The hydrological sensitivity of a mid-size basin in the Mediterranean region to global and regional climate patterns is presented in the current study, based on a methodology to generate a basin-scale, long-term monthly surface temperature and precipitation time series that permits modeling the basin’s runoff. To this end, the case of the Litani Basin was selected. This basin is located in Lebanon and is situated east of the Mediterranean Basin. It is known to have a diverse regional environmental setting. This selection was made, first, to point out the importance of the physical and topographical characteristics that cover coastal versus mountainous regions of the basin on its hydro-climatological response and, also to demonstrate the opportunity for conducting related studies in areas with limited long-term measured climate and/or hydrological data. Monthly precipitation and temperature data were collected from different resources including grid based, satellites and gauging stations. The Hillslope River Routing (HRR) model was selected to generate the basin’s discharges.
Due to the lack of long-term runoff data, synthetic daily precipitation data were generated from the available monthly data using a two-part gamma distribution and mixed exponential models in order to produce and examine the resulting watershed runoffs. The Litani Basin is shown to maintain a dry trend in the period between 1900 and 2008. In addition, different climate pattern teleconnections in correlation with basin response were illustrated. The results show significant correlation between many global and regional circulation patterns and Litani’s hydro-climatology. To this end, the basin's streamflow regime was investigated subject to the effects of various hypothetical and predicted climate change scenarios. The results suggest a significant effect of the combination of temperature rise and precipitation decrease on the streamflow regime of the Litani. The results of this study will support water managers, planners and river agencies incorporating the impacts of climate change on watershed hydrology during the development of the basin planning process.