As winter approaches, international hydrologists have issued a timely reminder about building on intermittent or seasonal non-perennial rivers and streams.
Dry for most of the year, these waterways are prone to occasional flooding but manmade structures can impede the flow of large volumes of runoff leading to property and environmental damage, Australian and American researchers warn in a new article in the journal Wiley Interdisciplinary Reviews: Water.
At the same time, the researchers point out more needs to be done to protect the future of these important watercourses, which may also provide water for wildlife and agriculture during wet months or drought periods.
“With growing global water shortages and ever-changing laws and management policies, it is important that more actions are taken to protect these rivers and their environs,” says lead author of the report Flinders University hydrologist Dr Margaret Shanafield, an SA Tall Poppy of Science 2021.
As global populations rise, many non-perennial rivers are subject to development and overuse as they run through semi-urban or farmland areas.
“Non-perennial rivers haven’t been studied as much as continuously flowing rivers so we need more studies of streamflow generation processes, water losses and flow variability to understand and protect these waterways – particularly as more people move to dry regions and because many of these regions are projected to get hotter and dryer in the future.”
In Australia’s parched landscapes, non-perennial streams feed lakes and wetlands and help refill important groundwater. Around the world, they support a rich diversity of flora and fauna vital to the environment.
Already hydrologists in the US, Australia and elsewhere are reporting a decline in the number of days non-perennial rivers run every year.
About half of the world’s flowing waterways are categorised as non‐perennial, meaning they do not have continuous surface water flow throughout the year.
In Australia, more than two-thirds of our waterways are non-perennial – including long reaches of our largest river system, the Murray-Darling.