Impacts of Climate Change on the Red Sea Region and its Watersheds, Saudi Arabia

This chapter evaluates the impacts of projected climate change (period: 2020–2100) on the hydrologic systems along the Eastern Red Sea coastal plain. Shuttle Radar Topography Mission (SRTM) data and Landsat Thematic Mapper (TM) scenes were used to delineate watersheds and their channel networks (155 watersheds) that collect precipitation over the Red Sea Hills in the Kingdom of Saudi Arabia (KSA) and drain toward the Red Sea coastal plain. Continuous rainfall-runoff models were constructed and calibrated for each of the 19 major watersheds (watershed area: 1,825–107,769 km²; total area: 176,683 km²). Regionalization techniques were applied to extrapolate catchment-specific parameters from proximal calibrated catchments (i.e., Wadi Girafi, which has an area of 5,057 km²). The calibrated Soil Water and Assessment Tool (SWAT), and climatic inputs from the Climate Forecast System Reanalysis (CFSR) database, and from Tropical Rainfall Measuring Mission (TRMM) measurements were used to calculate the partitioning (runoff, evapotranspiration, and potential groundwater recharge) of precipitation for the time period from 1998 to 2010. TRMM data were validated by comparing them to rain gauge data (period: 1998–2012; number of rain gauge stations: >100) across the study area. Downscaled outputs of the Community Climate System Model (CCSM4) were used to simulate (for the period 2020–2100) the effects of climatic changes on the selected 19 Red Sea watersheds. Findings indicate that (1) the average annual precipitation is 130 mm and the total annual amount is 23 × 10⁹ m³; (2) with time, precipitation will increase over the northern and central watersheds and decrease over the southern watersheds; and (3) global warming is causing a rise in sea surface temperature, enhancing evaporation, intensifying northerly and northwesterly winds and precipitation over the northern and central watersheds, and possibly causing shifts in monsoonal fronts and modifying precipitation patterns over the southern watersheds.