The main objective of this study was to calculate the economic value (including externalities) of a created wetland located in a peri-urban park in Catalonia, Spain. The wetland, which covers an area of 1 ha, was constructed in 2003 and receives a secondary treated wastewater flow of between 100 and 250 m3/day. The externalities of the wetland were evaluated using the travel cost method. The value of the wetland is expressed in terms of the price of the water that flows through the system, which is estimated to range from 0.71 to 0.75 €/m3. The value of positive externalities (1.25 €/m3) was greater than private costs (from 0.50 to 0.54 €/m3). These results constitute empirical evidence that created wetlands in peri-urban parks can be considered to be a source of positive externalities when used in environmental restoration projects focusing on the reuse of treated wastewater. This study also illustrates 1) the small influence of the hydraulic infrastructure depreciation costs on the private costs of constructed wetlands (less than 10%), and 2) the low investment costs of constructed wetlands in comparison with operation and maintenance costs (less than 10% of total private costs).
Keywords: cost-benefit analysis, net present value, reclaimed water, treatment wetlands, water reuse