Temporary waterways are dominant in dryland river networks, and occur throughout the world. There is a growing scientific recognition of their importance. They support high biodiversity and provide ecosystem goods and services. They are important conduits for exchanges of water, energy, material and biota, even when water is absent.
Despite these values, temporary streams are being degraded in many places, in part because their legal status is at best uncertain in many countries, meaning many are not considered in regulation, policy and management. In the US and in the EU their status is determined on a case by case basis. Australia is more inclusive and our approaches can guide other regions. To align policy with scientific thinking, temporary waterways should be recognised as part of the river network if they flow and connect to the network, and if they are habitat for obligate aquatic biota or terrestrial biota unique to dry river beds.
To better implement water policy in temporary waterways, there needs to be i) better mapping of temporary waterways - they can be recognised by the presence of defined channel banks and fluvially sorted sediments; ii) better methods to measure and predict flow intermittency; iii) better biological indicators to monitor and assess their ecological condition. Costs to recognise and manage intermittent systems have been estimated to be minimal and offset by resulting economic benefits, especially where people critically depend upon them. This paper is based on Acuña et al., 2014, Science 343:1080-1081, with full acknowledgement of all co-authors.