## Compute global risk for one objective at a location concerned by several reservoirs

VGEST computes iso-frequency curves for each reservoir and dispatch the task between reservoirs with the so-called New York City rule (Clark 1950). For each reservoir `r \in R`

and each day `d`

of the year isofrequency curves allow to get the probability of failure in the future for one objective `o`

depending on the active volume stored in the reservoir `V_r`

:

`F_{r,d,o}(V_r)`

For a downstream objective location concerned by several reservoir, we get a composite information for each reservoir:

In the example above, risk of failure at the station "ALFOR_16" for the drought threshold "Vigilance" is around 2% for the lake Yonne (Pannecière dam) and 4% for the lake Seine. Depending on the active capacity of each reservoir, the relevancy of each probability should be considered. So, is it possible to compute the global probability of failure in the future?

## References

Clark, E.J., 1950. New York Control Curves. Journal (American Water Works Association) 42, 823–827.