Artificial neural networks are alternatives to stochastic models even if th
e optimization of their architectures remains a tricky problem. Two differe
nt approaches in long-term forecasting of potential energy inflows using a
feedforward neural network (FNN) and a recurrent neural network (RNN) are p
roposed The problem of overfitting, particularly critical for limited hydro
logic data records, is addressed using a new approach entitled optimal weig
ht estimate procedure (OWEP). The efficiency of the two models using OWEP i
s assessed through multistep forecasts. The experiment results show that in
general, OWEP improves the models' performance and significantly reduces t
he training time on the order of 60 percent. The RNN outperforms the FNN bu
t costs about a factor of 2 longer in training time. Furthermore, the neura
l network-based models provide more accurate forecasts than traditional sto
chastic models. Overall, the RNN appears to be the best suited for potentia
l energy inflows forecasting and therefore for hydropower systems managemen
t and planning.