Assessing the sustainability in water use at the basin scale through water footprint indicators

This study aimed to assess the sustainability in water use at the basin scale through the water footprint (WF). The methodology proposed by the Water Footprint Network was integrated with a hydrological and water quality model and in-stream monitoring data to assess the WF in the Canale D'Aiedda Basin (SE Italy). The Soil and Water Assessment Tool was used to estimate runoff, evapotranspiration and nutrients in the runoff. A bootstrap technique, coupled with Monte Carlo simulations, was applied to evaluate the WF uncertainty related to the variability in input data and the unknown natural background level of nutrients in the surface waters. The WF at the basin scale was 124.4 Mm3, of which 78.3%, 17.4% and 4.3% was constituted by the WFgreen, WFblue and WFgrey, respectively. The crops with the highest mean crop water use were vineyards (752.6 mm), followed by olive groves (583.1 mm) and durum wheat (489.1 mm). For the surface water, the total WFblue was unsustainable because the actual runoff (Ract) was not sufficient to satisfy the irrigation requirements. The WFgrey was unsustainable because the Ract was not enough to dilute the pollutant load associated with the diffuse and point sources to reduce it to below the maximum acceptable concentration. The surface water quality was impaired more by the point sources than the agriculture. The proposed modelling framework could be useful for improving water resources management.