Stochastic Approach to Hydrological Dam Safety in the Framework of the New Dam Safety Standards in Spain

The approval of the Technical Safety Standards for dams and reservoirs in Spain in 2021 increased the hydrological safety requirements, being necessary to check if measures have to be implemented in dams designed according to the prior standards. Some of these dams have scarce instrumentation and lack of hydrometeorological data. This work proposes a simple but sounded fully-stochastic methodology for assessing the hydrological safety of dams within this situation, potentially applicable outside academia. The methodology has been applied to a case study based on a real dam, and compared the results obtained to those of the standard deterministic procedure. We have found that the fully-stochastic methodology leads to higher maximum reservoir levels for the same return period, leading therefore to more conservative results for the case study. On this regard, potential flaws have been detected regarding the hypothesis of the standard deterministic procedure, discussed and solved by the proposed fully-stochastic methodology, which accounts for the stochastic nature of variables such as rainfall temporal patterns and antecedent runoff conditions. Moreover, the proposed methodology can be adapted for accounting for operational variables such as the initial reservoir level when the flood event occurs, providing results that resemble more to the reality of nature and the reality of dam-reservoir systems