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Water regime

The presence of water and the pattern(s) of wetland water levels are primary drivers of virtually all aspects of wetland ecology.

Understanding the water regime of wetlands is important for Australian wetlands as many go through natural, often extended, dry phases and support a suite of specially adapted organisms. Conversely wetlands that hold water permanently are also valuable ecologically as they provide refugia for flora and fauna during naturally extended dry periods or times of drought, potentially making them a source of colonisers for nearby or connected ephemeral wetlands.

The regularity and intensity of flows can influence water plant growth Photo by DES

Quick facts

1841
flooding reached the highest ever levels in the Brisbane region. In Ipswich the waters rose '55 feet above the ordinary height of the Bremer'[1]
1877
All States were affected by drought with disastrous losses in Queensland. In Western Australia many native trees died, wetlands dried up and crops failed[4]

The main features of water regime include timing and predictability, frequency, duration, extent and depth, variability and rate of change[2].

Feature definition Definition
Timing or predictability
  • When water is present
  • Within year-patterns are most important in seasonal wetlands whereas among-year patterns and variability in timing are relevant to temporary wetlands.
  • Can mean the month or season when a flow event is likely to occur and can be determined annually, within a season, or over a decade
  • Predictability means the degree to which flow events occur at particular times of the year or at particular intervals of time.
  • Flooding is typically far less predictable in arid regions for any given year, where flood frequencies and timing depend on regional climatic factors and erratic local rainfall and run-off[3]. 
Frequency
  • How often filling and drying occur over time
  • Ranges from zero to frequent filling and drying in shallow wetlands many times throughout the year
  • For example, a 100-year flood means the size of flood that is equalled or exceeded once in 100 years. This 1-in-100 chance means that there is a 1% probability of such a flood occurring in any given year.
Duration
  • Period of inundation or the discharge event
  • Days to years, varying within and among wetlands
  • Rates of rise and fall may be important
Extent and depth 
  • The area of inundation and depth of water
  • Water depth affects light penetration and other variables
Variability
  • The degree to which these above features change at a range of time scales
Rate of change
  • Refers to the ‘flashiness’ or stability of a river system.
  • ‘Flashy’ streams have very rapid rates of rise in flow (and often of fall in flow). Stable streams have a steady pattern of flow, and any changes take place relatively slowly.

References

  1. ^ Telegraph. Australia floods: History of Queenslands worst floods. [online] Available at: http://www.telegraph.co.uk/news/worldnews/australiaandthepacific/australia/8256385/Australia-floods-history-of-Queenslands-worst-floods.html [Accessed 16 August 2012].
  2. ^ Boulton, AJ & Brock, MA (1999), Australian Freshwater ecology: prcesses and management, no. Australian Freshwater ecology:processes and management, Cooperative research Center for Freshwater Ecology, Gleneagles publishing, Australia.
  3. ^ Queensland Museum (2022), Wetlands of Queensland Book, p. 437, Queensland Museum, Brisbane, Queensland.
  4. ^ R., N (2009), Drought Assessment, Capital Printing Company, India.

Last updated: 14 August 2023

This page should be cited as:

Department of Environment and Science, Queensland (2023) Water regime, WetlandInfo website, accessed 27 October 2023. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/ecology/processes-systems/water/hydrology/regime/

Queensland Government
WetlandInfo   —   Department of Environment and Science