Case study:Restoration of R. Odelouca
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Project overview
| Status | Complete |
|---|---|
| Project web site | |
| Themes | Environmental flows and water resources, Fisheries, Hydromorphology, Monitoring |
| Country | Portugal |
| Main contact forename | Rui |
| Main contact surname | Cortes |
| Main contact user ID | User:Rcortes |
| Contact organisation | UTAD |
| Contact organisation web site | http://www.utad.pt |
| Partner organisations | |
| Parent multi-site project | |
| This is a parent project encompassing the following projects |
No |
Project summary
The Odelouca River, situated in the Algarve Region of southern Portugal is considered to have high conservation value because of the former presence of intact and floristically diverse riparian galleries along the large stretches of the river corridor (now cleared and submersed following completion of the Odelouca Dam in 2010) and the presence of critically endangered species such as the endemic fish species, the Iberian nase Iberochondrostoma almacai and the Iberian Chub Squalius aradensis and the presence of the Iberian Lynx Lynx pardinus (Fernandes et al., 2007; Hughes et al., 2012; Hughes et al., 2009; Hughes, Ferreira & Cortes, 2008; Hughes et al., 2010). The River Odelouca is situated in the Monchique Natura 2000 Network (PTCON0037).
The construction and completion in 2010 of the Odelouca Dam, ostensibly for improving water supply in the Algarve Region, has been highly contested. Initially embargoed as a result of protests presented to the European Commission (EC) by the Liga para a Protecção da Natureza (LPN) concerning violation of the area’s intrinsic conservation value and Natura 2000 status, construction finally went ahead following a ministerial decision (2005) to reactivate the dam under the condition, stipulated by the EC, that an extensive programme of monitoring, mitigation and compensatory measures be implemented to offset dam construction impacts and habitat loss.
The intact riparian corridors of the Odelouca basin were diverse in plant species. The original riparian communites of this basin have overstoreys of Fraxinus angustifolia, Salix atrocinerea, S. australis, Alnus glutinosa with sedges of Nerium oleander and Tamarisk africana and Erica lusitanicum. Community continuity and integrity changed along the watercourse, as well as habitat quality and diversity. The highest quality and most diverse riparian corridors occurred in the midsection of the course, most of which is now submerged by the Odelouca reservoir. Upstream and downstream, less well preserved corridors occur in a predominantly agricultural landscape. The lower course is the most degraded stretch in terms of habitat quality, subject to resectioning and canalization in some areas. In many places the riparian woody vegetation has been replaced by invasive reed and giant reed beds.
Monitoring surveys and results
Research actions included in the protocol were:
• characterization of the presently existing composition and structure of the aquatic and riparian vegetation in the Odelouca river and assessment of its integrity and longitudinal continuity;
• characterization of in stream habitats and banks; assessment of quality and degree of human disturbance;
• Characterization of key animal communities of the river banks (birds) and river channel (macroinvertebrates and fish) and their relation with riparian and habitat features and human disturbance;
• development of nursery practices for local woody species and best methodologies for field implanting during rehabilitation,
• The study of the functional role of riparian communities in shaping and structuring in-stream habitats and driving river processes.
o Application of this knowledge to the development of rehabilitation proposals for selected river stretches (next phase).
• Modelling abiotic and biotic changes resulting from river rehabilitation actions. Validation of the model results through biomonitoring.
The next phase of activities carried out following the work described above comprised:
• Development and implementation of a proposal for a programme of requalification and rehabilitation measures for Odelouca riparian galleries and fish habitats for selected river stretches;
• Monitoring of requalification and rehabilitation measures for Odelouca riparian galleries and fish habitats at sites situated along a selected reach of river.
A set of monitoring sites provides data that (i) enable validation of proposals based upon modelling results and in depth data analyses and (ii) to correct deviations from the original line of desirable change.
Characterisation of the Odelouca study site was carried out at a total of 30 sites in 2005 and 2006 covering almost the entire length of the river, except the final downstream tidal section (Fernandes et al., 2007; Hughes et al., 2009; Hughes, Ferreira & Cortes, 2008; Hughes et al., 2010). Sampling programmes comprised detailed phytosociological surveys, habitat quality surveys using the River Habitat Survey methodology (Raven et al., 2009) and sampling of biological quality elements comprising fauna and flora (BQE; benthic macroinvertebrates, fish, birds and macrophytes) and physicochemical parameters following WFD compliant protocols (INAG, 2008b; INAG, 2008c; INAG, 2008). The character of BQE was assessed in relation to longitudinal changes in habitat quality, including riparian quality (Fernandes et al., 2007; Hughes et al., 2009; Hughes, Ferreira & Cortes, 2008; Hughes et al., 2010). Using the KT method which divides the study area into groups of physically similar units and then assesses the extent of given pressures within each unit, habitat and riparian integrity and types of impact were quantified in the study area (Figure 4) allowing impact specific rehabilitation and mitigation measures to be drawn up (Fernandes et al., 2007; Cortes et al., 2002). The KT method can also be applied to characterise and resolve issues in the NWRM context. Macroinvertebrate communities were found to respond to key habitat elements particularly depth, flow and flow while fish species showed distinct distribution patterns in relation to large scale impacts related to changes in land use and river regulation. Bird communities associated with woods and associated features (canopy cover) predominated in the midsection but were substituted by aquatic and generalist species in the downstream reaches (Hughes et al., 2010; Hughes, Ferreira & Cortes, 2008a; Hughes et al., 2009b. Cuttings and seeds from all dominant woody species were collected and tested for survival in greenhouse conditions at ISA. Regional nursery managers have been encouraged to be actively involved in this process to debate and demonstrate greenhouse techniques for growing on local tree species. The well preserved middle course riparian communities, now cleared and submerged, were used as reference sites for the rehabilitation of the selected degraded river sections earmarked for rehabilitation. Emphasis was given to the river segment immediately upstream of the area to be inundated and to the river segment immediately downstream of the dam where minimal flow requirements for maintaining the aquatic biota are now applied. Habitat modelling (river 2D model) was be used to predict fish habitat preference changes according to suggested rehabilitation proposals (Boavida et al., 2011b).
Biophysical Impacts: description of the impact Biophysical impacts along the Odelouca River were primarily linked to (i) the process of river regulation such as major earthworks, changes in flow regime and associated biophysical processes (natural patterns of erosion and deposition) and habitat destruction (e.g. clearance of riparian galleries) and (ii) changes in land use due to agricultural activities (Fernandes et al., 2007; Hughes et al., 2009; Hughes, Ferreira & Cortes, 2008; Hughes et al., 2010). The large scale pressures describe changes in land use related to agriculture (e.g. the presence of monocultures) and associated physical impacts at lower spatial scales (river reach and habitat) to bank side and channel (clearance of native riparian vegetation, reinforcement and embankment of the banks to protect against flooding and maximize space for cultivation).
A subsequent programme of requalification, based mostly on natural engineering techniques, was carried out as part of an INTERREG SUDOE financed project called RICOVER (River Recovery in the SUDOE Region). A reach of over 7km in length, situated downstream of the now completed Odelouca dam, was selected and a total of 6 sites selected for intervention measures and subsequent monitoring. Three sites where no intervention measures were carried out were “set aside” as control sites for comparison with the 6 intervention sites as part of the ongoing monitoring programme. Summary of some of the natural/bio- engineering measures The construction works commenced in 2011 (Fig. 6, 7 and 8). Most of the natural engineering methods were used to rehabilitate highly eroded and degraded river banks as a result of human intervention (see Table 1) and are briefly summarized below: • Resectioning of river banks and placement of geotextile (in some cases pre-treated with herbicide) to prevent erosion, retain soil moisture, prevent (re)growth of weeds and invasive plants and create favourable conditions for planted native plants; • Construction of a crib wall and placement of stone filled gabions to stabilise river banks; • Planting of rehabilitated banks with native plant species, collected from cuttings and seeds in the area and grown on in local nurseries (e.g. Tamarix, Oleander, buckthorn and ash); • Construction of artificial islands in the river channel to augment habitat heterogeneity; • Clearance of invasive riparian plant species (Arundo donax and Acacia sp).~
The rehabilitated sites were monitored in 2011 and 2012 as part of the RICOVER project (benthic macroinvertebrate and fish fauna; physicochemical quality) and in 2013 – 2014 as part of a contract with Águas do Algarve, SA (River Habitat Survey – to assess habitat quality, sampling of benthic macroinvertebrate and fish fauna; physicochemical quality and phytosociological surveys of the river banks). Water Framework Directive compliant protocols are followed in the field, with the exception of the phytosociological surveys. • Total cost of the initial sub programme of compensation measure (avifauna, fish fauna, riparian galleries and monitoring studies) 5,430,664 € • Project RICOVER – Rehabilitation of the riparian galleries 267,636 €. • Ecological Monitoring of the Odelouca River is carried out by UTAD under contract to Águas do Algarve, SA. and is ongoing. Results show overall ecological status as “Excellent” and “Good”, despite the fact that the Monchique site continues to be heavily organically polluted. This anomalous result may be due to the innate “hardiness” of the Mediterranean BQE, which are adapted to the extreme environmental conditions of drought and flow and therefore may be more resistant (and therefore less responsive) to some types of impact.
Lessons learnt
Expect the unexpected: Planting carried out in the winter of 2011 was followed by an exceptionally dry spring and summer, which placed the planted native species under considerable hydric stress and presented a real threat to their survival during the 1st year. However, surveys carried out in 2013 show that although the plants had a “rough start”, most of them have survived. The Mediterranean climate is characterised by notable annual and interannual variation in precipitation levels as a result of different phases of the North Atlantic Oscillation or NAO (Hughes et al., 2012; Trigo et al., 2004). Negative phases result in higher precipitation levels while positive phases result in higher temperatures and lower precipitation levels. Although these large scale climate patterns are beyond the control of any rehabilitation or NWRM project, they must be taken into account as part of the programme of measures.
Poor local stakeholder engagement: The implementation of the characterisation programme and subsequent rehabilitation programme along the river banks was initially met with much suspicion and some resistance by local farmers and land owners. The local farmers’ general perception was that land that was subject to intervention was being taken away from them, that risk of flooding would be increased, that project personnel were “trespassing” although, according to Decreto–Lei 54/2005 (República, 2005), the river banks and channel are in the public domain (although access has never been refused, local residents and land owners remain suspicious) and that the native plants planted along the intervention zones were of no commercial value and should be replaced by fruit trees, for example. Future actions to alert and educate locals to the value of lotic ecosystems, the presence of threatened species and NWRM must be more effective and interactive.
Image gallery
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Catchment and subcatchment
Site
Project background
Cost for project phases
Reasons for river restoration
Measures
MonitoringHydromorphological quality elements
Biological quality elements
Physico-chemical quality elements
Any other monitoring, e.g. social, economic
Monitoring documents
Additional documents and videos
Additional links and references
Supplementary InformationEdit Supplementary Information
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