Grey water footprint assessment at the river basin level: Accounting method and case study in the Segura River Basin, Spain

Measurement and monitoring of the pollution in continental waters is one of the main challenges in water resources management as pollution is the principal cause of degradation of aquatic ecosystems, leading to the subsequent reduction of ecosystem services. The grey water footprint (GWF), defined as the volume of fresh water required to assimilate the load of pollutants discharged into water, is an indicator used to measure the degree of water pollution in a homogeneous unit The GWF allows examination and contrast of the impacts of different pollutants located in different geographical areas, although it can also be used to compare the contamination impact with other types of impacts, such as the water extraction in aquifers. Although the potential and the foundations of the GWF formulation are well developed, the existing methodologies for calculating the GWF are still in an initial stage, which complicates matters when dealing with complex cases due to the newness of this indicator. This paper aims to develop a methodology that is appropriate for the comprehensive evaluation of the GWF at the river basin level. The methodology proposed considered the load of pollutants discharged in a basin, simulating the anthropised water cycle. This simulation, conducted by combining a hydrological model and a decision support system, enabled the calculation of GWF under present and future scenarios and/or the ex-ante analysis of the impact of different river basin management policies (e.g., wastewater treatment, water reuse, the joint use of surface and groundwater). Owing to all these advantages, the GWF is a highly useful indicator within the framework of integrated water resources management The GWF assessment in the Segura River Basin (South-eastern Spain) highlighted both the validity and the general applicability of the methodology. The basin under study is affected by serious pollution issues and is one of the most complex exploitation systems in Europe. Additionally, fostering of the use of natural water resources, wastewater treatment actions, water reuse, desalinisation and external transfers are performed in this basin. The results indicate that the GWF of the Segura River Basin is greater than its renewable water resources, making it markedly unsustainable in both the short- and medium-term. (C) 2015 Elsevier Ltd. All rights reserved.