Climate Change Impact and Water Resources Management of Blue Nile River Basin, Africa

• Author / Creator

  Tariku, Tebikachew

• Climate change is likely one of the key challenges of the 21st Century for it could impact the livelihood, water and food security, economic growth and social well beings of countries worldwide. In recent decades the water resource of the Nile River Basin (NRB) has suffered from increasing demands from competing users, and more frequent and severe hydrologic extremes. This research addresses the climate change impact on the climate and water resources of the NRB, and to management of its water resources to mitigate such impacts.
  First, the sensitivity of the Regional climate model, Weather Research and Forecasting (WRF), in regional climate modeling of NRB was investigated using 31 combinations of physical parameterization schemes of WRF. Using the ERA-Interim reanalysis data as initial and lateral boundary conditions, WRF was configured to model the climate of NRB at 36 km resolution and 30 vertical levels for 1999-2001. WRF simulated more accurate surface air temperature (T2) and downward longwave radiation than shortwave radiation and rainfall for the NRB. The simulation of rainfall is more sensitive to planetary boundary layer (PBL), cumulus and microphysics schemes, while the simulation of T2 is more sensitive to land-surface model (LSM) and radiation, than other schemes of WRF. In summary, the following schemes simulated the most representative regional climate of NRB: WSM3 microphysics, KF cumulus, MYJ PBL, RRTM longwave and Dudhia shortwave radiation schemes, and Noah LSM.
  Next, WRF was used to dynamically downscale the future precipitation and temperature of NRB for the base period (1976-2005), RCP4.5 and RCP8.5 climate scenarios of four GCMs over NRB for 2050s (2041-2070) and 2080s (2071-2100). Under these downscaled climate scenarios, the annual precipitation of Blue Nile, Atbara, and Sobat river basin, Bahar El Ghazal and Lake Victoria regions are projected to change by about [-7, 14.2], [-19, 25.3], [-7, 39], [-5.9, 23], and [3.6, 27] % in the 2050s, and [-14, 25], [-22.5, 39], [-4.7, 60.4], [-11, 31], and [11.8, 41] % in the 2080s, respectively. The mean annual air temperature for sub-basins of NRB is projected to increase by 1.67–2oC in the 2050s, 2–2.5oC in the 2080s under RCP4.5, and by 2.5–3oC in the 2050s and 3.9–4.6oC in the 2080s under RCP8.5, respectively. Since most precipitation extreme indices are projected to increase, NRB could experience more severe and frequent extreme precipitation in future. Furthermore, extreme temperature indices of NRB are projected to increase (decrease) in warm (cold) night/days.
  Next, climate change impact on the mean and extreme streamflow of the Upper Blue Nile river basin (UBN) in 2050s and 2080s was projected by three hydrological models (NAM, VIC and Watflood models) driven with RCP4.5 and RCP8.5 climate scenarios of four GCMs downscaled by WRF. All hydrological models were able to accurately capture the flow dynamics in both calibration and validation periods. Mainly due to a projected increase in evapotranspiration, the median of mean annual streamflow of UBN is projected to decrease to by 7.6% with a range of -19.7 to 17.7% in the 2050s, and by 12.7% with a range of -26.8 to 31.6% in the 2080s. The ensemble mean of annual maxima (minima) of high return periods are projected to increase (decrease) in 2050s and 2080s by all hydrologic models, respectively.
  To assess climate change impact on the water resource of Blue Nile River basin (BNRB), from changes in the streamflow of BNRB simulated by VIC driven by RCP4.5 and RCP8.5 climate change scenarios of four GCMs downscaled by WRF for 2050s and 2080s, the maximum, median and minimum projected changes in streamflow for BNRB were estimated. These projected changes in streamflow for BNRB were used to assess climate change impact to its future water allocations using a stochastic dual dynamic model. The results show that the outflow from the GERD reservoir, or the annual flow of BNR at Khartoum is projected to increase under maximum, but will decrease under median and minimum projected changes in streamflow for 2050s and 2080s. Since the annual net benefit is projected to increase (decrease) under the maximum (median and minimum) projected change in streamflow, the potential impact of climate change should be incorporated in the future design and development of the water resources of BNRB.

• Subjects / Keywords

  • Climate Change Impact
  • Extreme flow
  • WRF
  • Regional Climate Model
  • Hydrological Models
  • NAM
  • VIC
  • Watflood
  • GCM
  • RCP Climate scenarios
  • Dynamic downscaling
  • Extreme Precipitation and Temperature
  • Optimization
  • Water management
  • Stochastic dual dynamic programming
  • Nile River Basin
  • Blue Nile River Basin

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R33B5WQ66

• License

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