Impact of dense reservoir networks on water resources in semiarid environments

The northeast of Brazil is a semiarid region where water scarcity is a major problem dealt with by the construction of dams. This policy generated a dense reservoir network in the region, resulting in a complex system. The impacts of the network have been assessed, and the results showed that the existence of a large number of small dams upstream the strategic ones, impact both negatively and positively the overall water availability. The negative effects of the network are mainly high evaporation losses from small reservoirs, and the fact that they add considerable complexity to the management of the system. On the other hand, the reservoirs generate a more democratic water distribution and higher energy rationality, as a consequence of the better spatial distribution of the water resources. In addition, sediment retention in the network leads to lower silting rate of strategic reservoirs, meaning lower temporal decay in water availability in the already water-scarce region.