Paired catchments with native vegetation as a reference for water quality in streams in forest plantation areas

Abstract

Fast-growing forest plantations can alter catchment hydrological dynamics and stream water quality, for example with turbidity increase after forest harvesting. It is essential that forest management operations be linked to the performance of environmental monitoring, making it possible to identify the magnitude of these changes and contributing to adaptive management aiming to reduce and/or mitigate such effects. The aim of this study was to assess if water quality parameters of native forest are suitable for use as a reference for hydrological monitoring of exotic forest plantations. The study evaluated the water quality values between catchments with Pinus plantation and native vegetation, comparing them with limits established in the legal framework (Resolution n° 357/2005). The results show that the values of the water quality parameters of the stream located in the Pinus plantation catchment are very similar to those observed in the native forest catchment, both of which are within the limits established by legal framework. Thus, for activities that promote few changes in physical-chemical parameters, such as in the case of forest plantations, it was observed that best water quality standard to be used as reference is the one established in streams under the influence of conserved native vegetation, whose geomorphological characteristics are similar, hence the importance of paired catchments. Therefore, the values observed in native forest catchment can serve as reference for establishing maximum permitted values (MPVs) that are more restrictive and consistent with the local reality of forest plantations.