"Ecosystems are silent water users," said Louise Korsgaard of the Technical University of Denmark, speaking at the IUGG conference in Perugia, Italy. "The values of ecosystem services supported by environmental flows are rarely included in international water planning. Loss of ecosystem services affects the poor most."
Korsgaard advocates the use of the Service Provision Index as a decision support tool that can put a value on the ecosystem services provided by environmental flows. She believes the approach can help internalize externalities and safeguard poverty reduction strategies. The calculations can be run from standard spreadsheet software, are flexible and it's easy to see the data that's being used.
The value of the service provision index tends to converge on a maximum as flow increases, but may also peak if the flow becomes too high. Assessing the optimum value of the flow involves expert judgement.
Korsgaard has carried out a case study for the East Rapti river basin in Nepal, looking at the value of fish production, recreation and tourism and biodiversity conservation services provided by the river.
"Explicit valuation of services sustained by environmental flows is possible and needed to inform decision-making," she said.
A discussion forum on environmental flows will be available by August at environmentalflows.net.