Temporal analysis of water-energy nexus indicators for hydropower generation and water pumping in the Lower Blue Nile Basin

Abstract

This study performs a temporal analysis of nine water-energy nexus indicators for hydropower generation and irrigation water pumping. The Blue Nile, a major tributary of the Nile, within Sudan is taken as an example to demonstrate the temporal evolution of the nine nexus indicators. The indicators are water-energy productivity, firm daily energy generation, percentage of days at power generation capacity, variation in daily energy generation, annual energy generation, highest daily pumping energy, lowest daily pumping energy, variability in daily pumping energy, and annual pumping energy. A daily calibrated and validated water balance model of the Lower Blue Nile is used to construct time series for the nine indicators from 1984 to 2016. Time series analysis is performed to detect significant trends and regime shifts in the nine indicators. The analysis reveals that the heightening of the Roseires Dam in 2012/2013, one of the dams in the study region, resulted in significant shifts in annual energy generation, percentage of days at power generation capacity, variation in daily energy generation, water-energy productivity, and annual pumping energy. The significant shift (an increase in this case) that occurred in the percentage of days at power generation capacity indicates that the hydropower capacity of the Roseires Dam could be raised to utilize its hydropower potential more efficiently. It is shown that annual hydro-energy generation in the study region is dependent on water availability in the dry season (November to June). The temporal analysis of the nexus indicators demonstrates ability to detect significant natural phenomena and human interventions in the hydrological system. Understanding the temporal dynamics of the water-energy nexus is key to efficient utilization of water and energy resources, especially in a basin like the Nile where considerable alterations to the headwaters are underway.