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Ecosystem Functions

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Water Supply

The role of ecosystems in providing water through sediment trapping, infiltration, dissolution, precipitation and diffusion.


ecosystem FUNCTION CATEGORY

Provisioning Functions


How does water supply contribute to ecosystem service provision?

Rain falls over Moreton Bay obscuring the view from the mainland to North Stradbroke Island.

Coastal processes play an important role in regulating atmospheric processes and providing our water supply.

This ecosystem function is closely associated with the hydrological cycle. Although the hydrological cycle is a global cycle that remains fairly constant over time, there are regional variations to the hydrological cycle and therefore regional importance and implications for the provision or loss of this function. At various places in the hydrological cycle in SEQ, water transfers from the atmosphere (e.g. in clouds) to the land (e.g. in soils, lakes and oceans), as it changes between vapor (e.g. mist) to a liquid (e.g. rain) and occasionally solid (e.g. hale) states.

The water supply function can generally be characterised as: 1) finite - there is a fixed quantity; 2) sensitive - it is easily degraded by human activities or use; and 3) irreplaceable - there are no substitutes. The hydrological cycle links regional ecosystem components of water, land and the atmosphere through precipitation, runoff, infiltration and evaporation. In contrast to other resources, no organism can survive in the complete absence of water, making it central to the resilience of ecosystems, species and all aspects of the other provisioning goods and services provided by ecosystems. Water supply replenishes the regional landscape with freshwater.

Table 1 presents the magnitude water supply contributes to different ecosystem services relative to other ecosystem functions in SEQ. Of all the provisioning functions natural ecosystems perform that potentially can benefit people, water provision is arguably the most important. The water supply function provides all the drinking water required in SEQ. The hydrological cycle provides water that after conventional treatment is fit for numerous human consumptive purposes such as drinking and aquaculture (to name a few). Agricultural activities are underpinned by the provision of water. Water captured through this function in natural storages such as soils, underground aquifers and lakes underpin many human activities. Water is vital to virtually all human endeavours within the region.  

Through the transferring of water through the atmosphere to land and through different states (e.g. gas to liquid), the water supply function purifies water, regulates pests and disease and buffers us from drought. It also transports minerals important to providing productive soils and arable land. As the change of state involves the exchange of heat energy, this function is important to maintaining a habitable climate. Many cultural values are related to this function (e.g. afternoon thunderstorms are common during summer in which many local residents associate with sense of place).

  

 

What is the temporal and geographic scale water supply operates at and services are delivered?

The benefits derived in SEQ from the water supply function can be in-situ (in position) or one directional (downslope). For example, rain falls and can provide benefits of natural irrigation to the food crops it falls upon. However, there is strong connection between this ecosystem function and the water regulation function. So water can be supplied in a specific location (such as a mountain top forest) but the fluid nature of water and the infiltration potential of soils means the potential benefits could be downslope over time.

The map to the right shows areas where the function water supply is expected to occur across SEQ. Data sets supporting the map can be found in the Quick Index. By clicking on the link below the map it will provide a more detailed view.

 

How do we know if we are degrading, maintaining or improving water supply in SEQ?

 

Lowland mists in the west of SEQ, Fernvale.

Links to other publications and websites

DEHP - Water Cycle
McJannet et al - Water Infiltration
Water Encyclopedia
USGS - Water Cycle
Floods & the Water Cycle

The importance of the water supply function is reflected in the high level of monitoring dedicated to it at national, regional and local scales. This function is usually measured by the Bureau of Meteorology who regularly records weather including rainfall across Australia (and therefore SEQ) and historical information on rainfall can be found on their website. Water supply levels being a function of sediment trapping, infiltration, dissolution, precipitation and diffusion, the full range of these processes is difficult to monitor across a whole region. SEQ Water and other state agencies do however regularly monitor water supply levels as stored in major dams in SEQ, which reflects the amount of rainfall and water entering our catchments and major storage areas.

The supply of water in terms of rainfall in millimetres is presented on radio and television news and weather channels. Together, rainfall and dam levels are presented as community information in these programs. Local landholders monitor private dam levels, soil moisture and often take localised rainfall measurements. Many households also monitor rainfall through personal weather stations and rain gauges. The supply of water that filters through to aquifers is harder to monitor and measure. However it is evident that aquifer levels have dropped significantly in some parts of the region.

 

How do we manage this ecosystem function in SEQ?

Although the importance of water supply is widely recognised, the hydrological cycle being a global phenomenon is dependent on management of this function on the global scale. On a regional scale however, SEQ can contribute to the management of this function and limit regional variation through the maintenance of tree cover, monitored through land cover maps and remote sensing.

Currently the management of this function can be characterised by treating symptoms rather than causes. For example, in times of low water supply SEQ residents were supported to install water tanks, they had water restrictions placed on them and/or more dams were built. As well, declining water quality is regularly reported through the Healthy Waterways Report Card. A recognition of the economic value of this ecosystem service is emerging, though the long timeframes involved in ecosystem restoration do not match well with shorter term needs. This ecosystem function is the responsibility of the Department of Energy and Water Supply.