Ecosystem services review of water storage projects in Canterbury: the Opihi River case

There is an ever‐increasing demand for freshwater that is being used for the purposes of irrigation and land use intensification in Canterbury. But the impact of this demand has lead to unacceptable minimum river flows. In an effort to resolve these problems water storage projects that hydrologically modify rivers are considered. In order to consider the full range of values of the impact of impounding rivers, local and regional governments are considering the use of an ecosystem services approach. Ecosystem services are the various benefits that people can obtain from ecosystems. In this report an ecosystem services review is undertaken using a method that evaluates each ecosystem service with a selection of indicators. Specfically, in order to adequately capture ecosystem services, both biophysical and socio‐economic indicators need to be considered. To demonstrate an ecosystem services review, the method is used to assess the impact of the Opuha Dam on the ecosystem services provided by the Opihi River. A summary table of the impacts of the Opuha Dam is developed. It shows that there is conclusive evidence for a positive impact on only one ecosystem service, that of Freshwater Supply. The impact on other ecosystem services is uncertain, mixed or inconclusive. The inconclusiveness in the ecosystem services review about the impact on many ecosystem services occurs because only a few ecosystem services are adequately captured by both biophysical and socio‐economic indicators. Hence, efforts are needed to develop further indicators for many ecosystem services. Once these indicators are developed, an ecosystem services index can be established to quantify changes to the level of ecosystem services