Ecological flow in southern Europe: implementation in temporary rivers

The European Commission in 2015, as part of the Common Implementation Strategy (CIS), defined the Ecological Flow (EFlow) in natural surface water bodies as “a hydrological regime consistent with the achievement of the environmental objectives of the WFD in natural surface water bodies as mentioned in Article 4”. These environmental objectives refer to (i) non-deterioration of the existing status, (ii) achievement of good ecological status in natural surface water bodies, and (iii) compliance with standards and objectives for protected areas. The Report does not define a standard protocol for setting an EFlow but it provides some recommendations.

The approaches for determining the EFlow, which must be defined in the River Basin Management Plans, are grouped into four classes hydrological, hydraulic, habitat, and holistic method. However, few methods have been specifically defined for temporary rivers. Most of these waterways have been poorly monitored in the past. The lack of historical hydrological and biological data in natural conditions ("reference") further complicates the definition of the EF.

This work analyses the implementation EFlow in the European Member States in Southern Europe under Mediterranean climate with specific reference to temporary rivers, which are the most common waterways in Spain, Portugal, France, Greece, and Italy. Through an examination of the case studies reported in the literature, a critical review of the methodologies adopted in these EU Member States for setting an EFlow has been carried out.

Results of this study showed that although all States have integrated into their legislation the EFlow recommendations by the EC, in several cases its implementation is not enforced sufficiently and several difficulties still exist in setting an EFlow. Case studies where the EFlow implementation was specifically designed for temporary rivers are still very few and most of the applications are based on hydrological methods. The paucity of hydrological and water quality data is the most important limit in setting an EFlow.