A methodological approach for prioritizing water reuse projects in agricultural irrigation: a case study in Spain

Water reuse is a strategic priority for Water Authorities in Europe to reduce the pressure on water resources. However, its implementation is lagging behind expectations largely due to financial concerns. In this context, there is a special interest to identify in which specific Wastewater Treatment Plants it would be interesting to add a Water Regeneration Plant, taking account of potential existing clients in the vicinity and the implied costs and benefits. This paper proposes a methodology to quantify the infrastructure and operation costs of project implementation, and the benefits generated by the additional water offer. An algorithm designs the distribution network, allowing for a quick infrastructure cost analysis. The methodology is applied to the Upper Guadiana in Central Spain, where irrigation led to the overexploitation of the local aquifers and the subsequent restrictions on water use. Taking account of the existing Wastewater Treatment Plants, candidate reuse projects are classified according to their benefit/cost ratio, showing large differences according to the location and potential use of the regenerated water. The methodology allows for a quick assessment of the costs and benefits implied in different reuse projects and scenarios, providing science-based evidence to support water policy decisions.