"Hydronomeas" is an operational tool for the management of complex water resource systems. The model is applicable to a wide range of hydrosystems, consisting of river branches, reservoirs, boreholes, pumping and hydropower stations, aqueduct networks, demand points, etc. The model implements the parameterisation-simulation-optimisation scheme. The former refers to the formulation of parametric control rules for the major infrastructures (reservoirs, boreholes), where the number of parameters is kept as low as possible. Simulation is applied to faithfully represent the processes. Specifically, real economic values in addition to virtual costs are assigned to network components to preserve the physical constraints and water use priorities, ensuring also the lowest-cost transportation path of water from the sources to the consumption. Finally, optimisation is applied to derive the optimal management policy on the basis of multiple performance criteria, thus ensuring simultaneous minimisation of the risk and cost of decision-making. Note that the modelling framework adopts a stochastic approach, providing predictions for all hydrosystem fluxes (storages, discharges, withdrawals) on the basis of synthetic scenarios of inflows.