The aim of this work is to analyze the extent to which the demand-related uncertainty and long-term effects impact the optimization of the operation of a small hydropower system (SHPS). To this end, a SHPS is assumed to be installed in a real Alpine water distribution system, and its settings are optimized in order to investigate the SHPS long time performance (10-year simulations with EPANET 2) under different future scenarios. Results show that neglecting demand uncertainty and the long-term sequence of demand patterns prevents obtaining a realistic assessment of the profits connected with the SHPS operation. Furthermore, the issue of setting optimization is marginal compared to that of uncertainty assessment and long-term effects.