TECHNOLOGY: URBAN IRRIGATION CONTRIBUTION TO URBAN GREENING: A REVIEW SNAPSHOT • The benefits of green space in urban settings are many – from contributing to personal wellbeing and mental health, to cooling and aesthetics – and planners and designers are looking more to incorporate green areas in cities and towns • Geoff Connellan describes some of the major changes occurring in urban planning and the green environment and their implications for irrigation • Factors being considered in planning include the impact of climate change on irrigation management and species to be grown, passive irrigation, the use of technology in helping provide green areas and ways for demonstrating water use efficiency
to maintain soil moisture and that spaces previously not irrigated or irrigated at a low level, may now need to be irrigated at higher rates. There are a range of scenarios and situations where irrigation will be required and demand for water supplies will increase, including the following: • for higher quality turf surfaces • to promote rapid grass recovery from increased use and wear • for lawn areas for recreation use within parks that are otherwise not irrigated • for providing conditions that meet street tree soil moisture needs • to secure water supplies for dry and drought periods • for meeting increasing demands from climate change.
Climate change impact
The structure of the urban environment is changing. There is now more emphasis on green infrastructure, which includes green roofs, green walls, pocket parks, urban forests and feature landscapes. The intent is that these spaces and elements will provide multiple benefits to the community. Exposure to and experience of these spaces has been shown to contribute to the wellbeing of individuals. In this article, Geoff Connellan examines some of the changes occurring in the urban green environment and the role of irrigation. Parks provide a range of green services including cooling, habitat, aesthetics and the opportunity to experience nature, all of which have been shown to have mental and physical benefits. The role of parklands in providing spaces for the community for recreation and enjoyment has been highlighted during the COVID-19 pandemic.
Planning is the key Lawn spaces where people can sit and relax and trees and landscape plantings that are healthy are needed to provide these green services. Planning needs to consider how they can be delivered. As part of this planning, the design of the space and of landscape plantings is crucial. To deliver target benefits, plants need to be healthy and provided with conditions that enable them to grow and develop. This means that irrigation will generally be required
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The impact of climate change on how we manage green space in the future is an important consideration for planners. Climate change will affect irrigation management through the increased deficit between evaporation and rainfall. For south-eastern Australia forecasts (2090), rainfall reductions will be around 10 per cent and evaporation will increase by 9 per cent. This represents a deficit of 19 per cent which will need to be satisfied. While 2090 may seem a long way off, some trees planted today will be experiencing the 2090 conditions. Adding to the deficit are predicted significant reductions in runoff from catchments. The bottom line is that many existing trees will need irrigation to meet the stress conditions in the coming years.
Water for greening - passive and active irrigation While urban green spaces have been and continue to be heavily dependent on potable mains supply, there is now a focus on developing alternative sources, in particular, rainwater and stormwater. Many schemes have been developed where stormwater is retained in the local area and used directly or indirectly, through harvesting and storage, to irrigate green spaces. Passive irrigation, where rainwater and stormwater are directed to landscape plantings, including trees, is a logical strategy to enhance plant growth and provide some level of protection against dry conditions. It is certainly a viable option for many urban landscape situations. Some of the characteristics and properties of passive irrigation that need to be considered by planners and designers are listed over the page.