This paper studies the problem of non-cooperative water allocation between heterogeneous communities embodied in an acyclic network of water sources. The extraction activity of a community has a negative impact on the extraction activity of its direct successors: it reduces the intensity of water flows entering their source, and thus, increase their convex costs of water extraction. We show that the equilibrium profile is unique and may be expressed through complementarity and substitutability effects which sharacterize the incoming centrality of a community in the network of sources. For each community, the efficient activity is a combination of two opposite network effects, the incoming centrality and the outcoming centrality. Then, the optimal tax rate imposed to a community depends on the network structure, and reflects both the marginal damages and the marginal benefits this community delivers to other communities at the efficient extraction activity profile.
