Will a nonstationary change in extreme precipitation affect dam security in China?

Due to the changing climate and environment, the stationary assumption used to calculate the design precipitation or flood of dams is no longer suitable, threatening dam reliability and safety. To see whether nonstationary changes in extreme precipitation will impact existing dams in China, we quantify the exceedance of extreme precipitation over the design intensity by the impact level (R), where the future extreme precipitation intensity is calculated from the nonstationary generalized Pareto (GP) distribution. We mainly focus on medium- (reservoir capacity greater than 0.1 billion m(3)), large- (reservoir capacity greater than 1 billion m(3)), and super-sized dams (reservoir capacity greater than 10 billion m(3)), which have design return periods longer than 100 years. We find that about 15 %-20 % of regions in China may have significant increases in extreme precipitation in the future, mainly in the southeast and northwest. 15 % of medium- and large-sized dams of China may be significantly affected (R greater than 50 %), and more dams are expected to be affected by 1-DAY (156) and 3-DAY (149) precipitation, compared as opposed to 5-DAY (128) precipitation. For super-sized dams, there is no possible significant impact in any of the basins (all R < 100%) by 2100 under the current nonstationary assumption, but results using CMIP6 data show that dams over the Zhujiang River Basin and Xinanjiang River Basin are expected to be impacted (R greater than 100 %) under the SSP585 scenario. However, under the SSP126 scenario, the impacts of extreme precipitation are consistent with the nonstationary analysis results, which suggest non-significant impacts in all basins.

Automated summary

The study found that in the future, about 15% to 20% of regions in China may experience significant increases in extreme precipitation, mainly in the southeast and northwest. 15% of medium and large-sized dams in China may be significantly affected, with more dams expected to be impacted by 1-day and 3-day precipitation compared to 5-day precipitation.