Effects of the Indian Ocean Temperature on Nile River Flow Volumes

Egypt and Sudan are heavily dependent on the Nile River for sustaining their populations. In high flow years, the Lake Nasser surface water levels rise and overflows filling surrounding natural depressions and forming additional lakes (Tushka lakes) in peak flow years. The underlying Nubian Aquifer is recharged in high flow yeas, whereas the Nubian groundwater discharges into the Nile in low flow years. Previous studies have shown that the variability in flow volumes in the Nile River can be partially (~30%) accounted for by variations in the intensity of El Niño Southern Oscillation (ENSO) events. Other previous studies suggested that rainfall in the upper Blue Nile catchment in Sudan can be linked to changes in the intensity of temperature variations across the Indian Ocean (the Indian Ocean Dipole or IOD). To test which of these events correlate best with Nile flow volumes, Nile flow records in the Blue Nile (above Khartoum), the White Nile (above Kharthoum), and combined flow at Wadi Halfa covering the time period from 1902 to 1962 were analyzed together with SST measurements. Peak and minimum discharge, and quarterly measurement from each gauge were obtained. The intensity of El Nino 3.4 and 4, and of the Indian Ocean Dipole variations from the reconstructed SST dataset hadlSST covering the same time period were used. The best correlation was found to exist between fluctuations in the IOD in the Spring (Apr-May-Jun) preceding the peak flow (usually occurring in August) and maximum discharge at the Blue Nile Gauge above Khartoum (Correlation coefficient of 0.65). Variations in El Nino intensity for the same time period showed lower correlations with peak and base Nile flow in the Blue Nile (0.55). This indicates that the intensity of the Indian Ocean Dipole has been a better predictor than El Nino for peak Nile Flow volume. Results highlight the potential for using the latter relationship for predicting Nile Flow volumes flowing in Lake Nasser and for modeling the corresponding recharge and storage in the Nubian Aquifer under future model climatic scenarios.