Effects of water quantity on connectivity:the case of the upper Parana River floodplain

摘要

The hydrological regime is the main force driving processes in river-floodplain sys-tems. The flood pulse concept serves as a base from which to study the processes acting in such a system. However, when the flood pulse is regulated and there is a need to re-establish the hydrography at close to natural conditions, the best way to achieve this is via ecohydrology, a newly emerging paradigm. In this paper, we use principles of ecohydrology to evaluate the effect of water quantity on the limnology, biota and fishery of the upper Parana. River systems, where a UNESCO demonstra-tion site on ecohydrology is located. In addition, we argue that dam operation can be crucial for restoring the hydrography of the Parana River to near natural conditions. The data used were collected between 1986 and 2006 in several habitats of the flood-plain. The limnology, biota (periphyton, phytoplankton, zooplankton, benthic inver-tebrates, fish, macrophytes and riparian vegetation) and fishery (ecosystems services) were all influenced by the alteration in the hydrography prompted by the functioning of the dams located upstream from the demonstration site area. Moreover, the observed deterioration of the water quality due to the presence of toxic cyanobacteria is another strong argument for adjusting the dam's operation to re-establish the tim-ing of the floods to match critical periods of the biota in order to restore ecosystem biodiversity and services.