hydroeval.rmse hydroeval.rmse(simulations, evaluation) Root Mean Square Error (RMSE). Calculation Details \[E_{\text{RMSE}} = \sqrt{\frac{1}{N}\sum_{i=1}^{N}[e_i-s_i]^2}\] where N is the length of the simulations and evaluation periods, e is the evaluation series, s is (one of) the simulations series.