Ecological flow in southern Europe: implementation in temporary rivers

The European Commission in 2015, as part of the Common Implementation Strategy (CIS), definedthe Ecological Flow (EFlow) in natural surface water bodies as "a hydrological regime consistentwith the achievement of the environmental objectives of the WFD in natural surface water bodiesas mentioned in Article 4". These environmental objectives refer to (i) non-deterioration of theexisting 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 astandard protocol for setting an EFlow but it provides some recommendations.The approaches for determining the EFlow, which must be defined in the River Basin ManagementPlans, are grouped into four classes hydrological, hydraulic, habitat, and holistic method.However, few methods have been specifically defined for temporary rivers. Most of thesewaterways have been poorly monitored in the past. The lack of historical hydrological andbiological 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 Europeunder Mediterranean climate with specific reference to temporary rivers, which are the mostcommon waterways in Spain, Portugal, France, Greece, and Italy. Through an examination of thecase studies reported in the literature, a critical review of the methodologies adopted in these EUMember States for setting an EFlow has been carried out.Results of this study showed that although all States have integrated into their legislation theEFlow recommendations by the EC, in several cases its implementation is not enforced sufficientlyand several difficulties still exist in setting an EFlow. Case studies where the EFlow implementationwas specifically designed for temporary rivers are still very few and most of the applications arebased on hydrological methods. The paucity of hydrological and water quality data is the mostimportant limit in setting an EFlow.