Key lessons:
- Artificial water retention measures (i.e. dam) do induce significant hydromorphological pressures on streams, thus hindering, among other things, natural water retention capacity downstream.
- Forested riparian zones deliver a number of ecosystem functions and services such as storing and fixing carbon; serving as wildlife habitats and ecological corridors; stabilizing riverbanks; providing shade, organic matter, and food for streams and their biota; retaining sediments and filtering chemicals (fertilizers and pesticides). Therefore, further to their effect on water yield, they contribute to a wide range of benefits for society.
- Riparian afforestation is by no means just about planting trees but also about introducing other vegetation types such as scrub, mostly through laterally recovering space for the river. Afforestation is compatible (and there are synergies indeed) with riparian clearing (in this case of invasive species).
- Although there is still no evidence available for the Odelouca sub-catchment, it all suggests that nitrogen levels can be reduced in rivers (by plants or microbial denitrification) through forcing water to circulate through afforested riparian buffers.
- The Odelouca case study is a good example about the characterization and assessment of intermittent Mediterranean river systems for restoration and requalification measures, including bioengineering techniques, closely related to green infrastructures.
- Monitoring is critical. River Habitat Survey (RHS) is a good way of assessing habitat quality including riparian complexity, diversity of hydromorphological features and artificialisation of aquatic habitats (features that may affect facets of the local water cycle).
- Riparian vegetation is central to the physical, chemical, and trophic health of streams. However, riparian restoration is still its formative stage and can be a complex process.
- Further efforts on the ex-post assessment of the impacts of vegetation changes on seasonal water yield and flow regime would be required.