This a video tutorial of the TREHS open access software tool. TREHS has been developed within the LIFE+ TRivers project (LIFE13 ENV/ES/000341) with the aim of improve the management of temporary rivers. This software allows for the input and storage of hydrological information coming from flow simulations, flow gauging records, interviews made to local citizens, in situ observations, and interpretation of aerial photographs. River regime is then classified based on this information, using a new categorization that takes into account the frequency of the three main aquatic phases: flow, disconnected pools and dry river bed. Up to six metrics describing these frequencies and their temporal patterns of occurrence are used to determine the natural and observed river regime. TREHS also characterizes the differences between the natural and observed regimes, performs a diagnosis of the hydrological status (degree of hydrologic alteration) along with an assessment of the significance and robustness of this diagnosis, and recommends the best period for biological quality sampling. Finally, in order to evaluate the ecological status, TREHS also allows calculating hydromorphological and biological quality of a river stretch.