The implementation of small hydropower systems (SHPS) in existing Alpine Water distribution systems (WDS) is a meaningful strategy for the reduction of CO2 emissions. Typically, the water consumption patterns of one or several representative days are used for the design procedure of these systems. For the design of the SHPS in WDS, the most important issue is to preserve the water supply without constraints. However, regarding water quality issues (especially related to water age), SHPS can exert a positive influence on the WDS performance. In this study, a long-time simulation model (10 years) is established for a WDS model and is subsequently used for the design of the SHPS. This study is performed to establish a more efficient design of these systems and to evaluate the long-term effects on the pressure and water quality issues, i.e., water age. With a simulation time over one decade on an hourly basis, full load hours and water flows for different turbine sizes are determined in detail. Based on that information, the detailed design and optimisation of the SHPS were performed, and the most cost-efficient device size was determined. (C) 2014 Elsevier Ltd. All rights reserved.