Thread by @davidhelms570

#KakhovkaReservoir #KakhovkaHPP Status Follow-up: 8 May 2023. Upon further analysis of 6 May 2023 Sentinel-2 imagery and consultation with @tom_bike @Gergyl & @BruckenRuski, we believe the #KakhovkaReservoir water is "over-topping" the #KakhovkaHPP dam. /1

https://twitter.com/davidhelms570/status/1655226067425062912?s=20

Time-series loop from 27 March 2023 to 6 May 2023. Note the "brightening" downstream (left side) of the #KakhovkaHPP sluice gates last frame in loop which is water flowing over the top of the dam. Over-topping is particularly evident on the 3 northern most sluice gates. /2

Why is this happening? Recall the Russian occupiers blew up the road and rail deck above the #KakhovkaHPP dam sluice gates on 10 NOV 2022 as part of the RF retreat ("strategic repositioning") from the Dnipro right bank. /3

https://twitter.com/bayraktar_1love/status/1591370252474253313?s=20

The damage to (removal of) the road and rail deck allowed the right bank (north-side) sluice gates #26-28 to be visible using satellite and drone reconnaissance. This is why the 6 May 2023 Sentinel-2 image shows over-topping of these sluice gate more readily in that section. 4/

What is the impact to structural integrity of #KakhovkaHPP dam from over-topping? We can't say with certainty, but as long as the water is flowing over the concrete raceways, the dam should be stable. However, persistent water over-topping forces risks damaging the gates. 5/

What should we look for in the near future? Over-topping may continue through the Dnipro spring peak water flow which should last through June 2023. Water which otherwise would be diverted from #KakhovkaReservoir to the Kakhovsky and Dniprorudne Channels is not being diverted. 6/

Russian occupiers have destroyed most of the hydro-technical facilities in occupied Kherson and Zaporizhzhia in addition to disabling #KakhovkaHPP ability to manage water discharge rates by destroying the lock, the HPP turbines, and gantry cranes. 7/

Dnipro river water which would otherwise be diverted or allowed to flow downstream is being retained in the #KakhovkaReservoir thereby raising the water level as a consequence of Russian destruction of water management facilities. 8/

The good news is, for now, #KakhovkaHPP dam is stable with minimal chance of downstream flooding and the #ZaporizhzhiaNPP has sufficient access to water. The risk of catastrophic dam failure remains as long as Russian occupiers control #KakhovkaHPP. 9/

In summary, #KakhovkaHPP water over-topping is occurring and could last through the end of June 2023. We believe risk to the dam integrity is not threatened at this time. 10/

cc/ @iaeaorg
@energoatom_ua
@DefenceU
@Ukrhydroenergo
@pwebbr
@ResponsibleSci
@eugenesimonov2
@NFLAUKandI
@BrianKuns
@PeterGleick
@DetectorMedia
@a_prokip
@USDAForeignAg
@MarkHibbsCEIP

@threadreaderapp please unroll