Thread by @sebastiansterl

(1/22) Our new paper @NatureEnergyJnl (rdcu.be/cikbq) proposes a solution to break the deadlock in negotiations between #Ethiopia 🇪🇹, #Sudan 🇸🇩 & #Egypt 🇪🇬 on the Grand Ethiopian Renaissance Dam (#GERD) on the #BlueNile – with help of #solar and #wind power. Thread👇

(2/22) The #BlueNile (Abay) is highly seasonal, with extreme differences in flow between dry and wet months. #GERD’s reservoir is so large it can store the full annual flow & deliver #hydropower at a stable rate throughout the year - suppressing the river flow #seasonality.

(3/22) Delivering hydropower w/o seasonality makes loads of sense from Ethiopian perspective, but overhauls natural timing of water reaching #Sudan & #Egypt. Behind many disagreements on #GERD lies downstream countries’ fear of s/o upstream having control over #BlueNile flow…

(4/22) What have #solar & #wind power (VRE: variable renewables) got to do with this? Like river flow, the region's sunshine & winds, too, are highly seasonal. But here’s the point: their profile is OPPOSITE to that of river flow. In 🇪🇹🇸🇩 VRE is strongest during the DRY season.

(5/22) Hydro plants like #GERD can be used flexibly to "firm up" intermittent VRE year-round, 24/7. What if GERD were operated in this way? Given the seasonality of VRE in the region, GERD #hydropower production would have to be relatively low in dry season, high in wet season.

(6/22) We design 4 scenarios to showcase what this would mean for GERD outflow: S1 (GERD operated independently of VRE), S2 (GERD operated w/ VRE in 🇪🇹), S3 (GERD operated w/ VRE in 🇪🇹+🇸🇩), and S4 (same as S3, but w/ so much VRE that full range of GERD flexibility needed).

(7/22) Now, the crucial point: This would *reintroduce* #seasonality in #GERD outflow, mimicking natural pattern. Without VRE this would make no sense (since ETH power demand isn't very seasonal, cf. S1) - but w/ lots of VRE (S2-S4), it’s a very logical approach to operating GERD

(8/22) What would that mean for 🇸🇩🇪🇬? While #Ethiopia would have all benefits of a big dam, for #Sudan+#Egypt, it would look as if Ethiopia only built a modest, relatively small reservoir. Many such reservoirs already exist on the #Nile, whose presence is uncontested.

(9/22) Interestingly, this works BETTER in a joint Power Pool w/ countries trading electricity. E.g. VRE in Sudan is a better complement to GERD’s hydro than VRE in Ethiopia. Hence, there are mutually beneficial links between the sharing of #energy resources & #water resources.

(10/22) Next to increasing VRE penetration and reducing downstream objections to GERD operation, synergetic GERD-VRE operation has various other benefits - e.g. it improves compliance w/ environmental flows in Sudan, while still protecting Sudan from extreme droughts and floods.

(11/22) Synergetic GERD-VRE operation would also dispel any allegations that #GERD is "oversized" – the alleged oversizing actually becomes an asset for #Ethiopia with increasing VRE infeed, because VRE benefits from the high “operating reserve” of GERD.

(12/22) Further, by retaining seasonality in #BlueNile flow, the timing of water reaching #Egypt’s High Aswan Dam (HAD) wouldn't be drastically overhauled - so there won't be prolonged periods in which #GERD fills up while #HAD empties, thus assuaging Egypt’s anxiety over GERD.

(13/22) Our simulations cover 26 years of river flow, and thus contain information on extremely dry years as well. Under all scenarios, GERD can mitigate the extremes in natural flow. Egypt+Sudan will benefit from GERD by receiving more water during dry years than previously.

(14/22) What does this mean for the ongoing talks around a tripartite agreement for GERD operation? We suggest that such an agreement could be centered on *energy*, not *water* objectives - eg Ethiopia operating GERD in synergy w/ large VRE fleet in Eastern Africa Power Pool

(15/22) Given all of the above, such an agreement would reassure Egypt+Sudan that GERD does no harm; meanwhile, as Ethiopia wishes, it would decouple GERD talks from overall water sharing issues, bc agreement would be centered on energy, not water.

(16/22) If #Ethiopia pursued similar operational schemes for its other #hydropower plants, it could integrate massive amounts of #solar and #wind power on its electricity grid, diversifying its power mix. ETH power generation by 2030 could be nearly 50% #VRE.

(17/22) On the long term, this will help Ethiopia lower electricity costs. Thanks to ever-plummeting #solar & #wind power costs, the time that these will become cheaper than #hydropower is fast approaching. Sudan, too, would benefit - displacing #fossilfuels with hydro-firmed VRE

(18/22) At the same time as VRE costs are plummeting, massive #hydropower projects are falling out of favour with international donors, and the #ParisAgreement strongly discourages new #fossilfuel investments. Our proposed solution fits well into these worldwide trends.

(19/22) In summary: To support the ongoing #GERD negotiations between #Ethiopia, #Sudan & #Egypt, we call for integrated hydro-solar-wind planning to be taken up in the talks as soon as possible. It could be a win-win-win-win-win situation for the region.

(20/22) Tagging a few who may be interested: @TirusewAsefa @WeAspire @eipsa_nile @nbiweb @Antex_GD @Mekdi_Messay @anacascao @Haimanotwua @MulugettaYacob @mzjacobson @ChristianOnRE @oyewo_solomon @iyoba4u @grand_gerd @AfeworkDagim @Presidence_RDC @_AfricanUnion #Nile #Abay #GERD

(21/22) Finally, big thanks to co-authors Dalia Fadly (@KU_Leuven), Stefan Liersch, Hagen Koch (both @PIK_Climate), @WimThiery (@VUBrussel), and an anonymous Ethiopian fellow researcher for inspiring discussions and great collaboration.

(22/22) Link to article: nature.com/articles/s4156…