Technical Reports

Irrigation of Urban Green Spaces: a review of the Environmental, Social and Economic benefits

Fam, D., Mosley, E., Lopes, A., Mathieson, L., Morison, J. and Connellan, G. (2008). Irrigation of Urban Green Spaces: a review of the Environmental, Social and Economic benefits. CRC for Irrigation Futures Technical Report No. 04/08.

Executive Summary

For the first time both urban and rural communities are together experiencing drought. In most cities and towns across the country mandatory water restrictions have been in place for the last four or five years. These restrictions have reduced consumption by 14 - 28% and impacted on 75% of Australia’s population. But long-term water restrictions come at a cost. Implied costs have been put in the order of $1.6 – 6.2 billion each year.

In this report a comprehensive review is provided of the benefits of urban green spaces and the potential impacts of long-term water restrictions on parks, sports grounds and public gardens. This sector is estimated to account for 27% of the implied cost of long-term water restrictions. A Triple Bottom Line approach is used to examine the environmental, social and economic benefits of urban green spaces and the maintenance of these values using irrigation during drought. The economic aspects are broadly covered in this report. A specific CRC of Irrigation Futures report attempts to make a dollar value estimate of the benefits of urban open space in two case study areas (benefits transfer method).

Urban green space impacts significantly on the micro-climate of a region by modifying extremes of climate, improving the hydrological cycle and improving plant health and biodiversity and adding to soil stability. Most of these advantages are dependant on the vegetation being maintained by irrigation during drought.

Urban vegetation can have a cooling effect of between 2 – 8ºC due to increases in evapotranspiration. This can reduce building energy consumption by 7 – 47%.

Urban green spaces can have a positive impact on the hydrological characteristics of the highly modified urban catchments. Grasses and treed areas increase water infiltration and slow run-off after rainfall. These areas are also effective at removing significant amounts of pollutants such as phosphorus, lead and nitrogen and fine sediment.

Urban parks and golf course can be important ’hotspots’ of biodiversity in cities. During drought, irrigation of these areas can provide an important refuge for fauna.

The literature indicates that green space can positively affect a person’s physical and mental health, and reduce the risks of contracting lifestyle diseases. Further social benefits are shown from the use of green space for participation in sporting and recreational activities. Communities as a whole also benefit from green space from an aesthetic perspective, and by its contribution to improving social cohesion.

The documented research on the positive effects of nature, including urban green spaces, on blood pressure, cholesterol and stress-reduction is suggested to be enough to call for its inclusion into Australian National Health Priority Areas. In a novel transformation, London’s Trafalgar square was transformed into a 2,000 m2 village green for two days as part of ‘London’s Villages’ campaign in May 2007. ‘People were bowled over by the calming effect on everyone. It was amazing to see the contribution that grass made in transforming urban space’.

The lack of irrigation has caused the condition of sports grounds to decline significantly to the point where some are not able to be used due to the injury risk to players. Contrary to the implied value of ‘saving water’ that dominates popular thinking, maintaining urban green areas such as public parks, private gardens and sporting ovals in the face of water restrictions and rapid urbanisation is necessary for the physical, psychological, emotional and spiritual needs of a healthy community.

Urban green spaces improve residents’ ability to cope with life issues in urban housing projects. When trees and greenery were immediately outside their apartments, inner city residents coped better with the demands of living in poverty, felt more hopeful about the future, and managed their most important problems more effectively.

The impacts referred to in the previous section have two broad areas of economic implication. Firstly, green open space facilitates a commercial, income-generating outcome from festivals and sporting events. The second type of implication is an economic efficiency effect resulting in an increase in net social welfare, typically in the form of reduced costs to society, such as reduced health care costs, reduced pollution, etc. but also impacting on non-priced or non market benefits such as community cohesion, aesthetic values, wildlife habitat, etc. There is another economic efficiency, earmarked for further research in an Australian context in this report, which is the potential cost-saving in building energy consumption by the inclusion of green space.

At the end of June 1997 there were 52,164 Australian parks and gardens covering 3,386,354ha which employed 16,646 workers at a cost of AU$470.2 million dollars in wages (ABS 1998). This is a significant amount of financial investment and employment in Australia’s economy and needs to be recognised when decisions need to be made regarding water application to public open green space.

These urban green spaces have beneficial ‘flow on’ effects to neighbouring properties. Residential properties with well maintained gardens and properties close to green public spaces are valued approximately 10% higher.

This report summarises the environmental, social and economic benefits of urban green spaces reported in the literature. Across the broad range of areas clear benefits are evident. The report links the salient environmental and social benefits to potential economic benefits in offsetting the costs associated with energy consumption, water quality and air pollution control, physical and mental health, crime prevention and community building. It has however also identified a lack of Australian economical data on the benefits of urban irrigation across both environmental and social aspects.

Its findings suggest that further research would be needed to clarify the benefits of the irrigation of urban green space across the Triple Bottom Line. Suggested areas of key and additional further research, which would be needed to document and quantify these benefits in an Australian context, are listed in the conclusion of the report.

CRCIF-TR0408-web-final.pdf ( 1,348kb )