Analysis: rainwater harvesting is a possible small solution to some very big problems - and not just watering the garden.
By Ruth Quinn, ATU Sligo
Rainwater harvesting has been used for centuries as a supplementary water source during dry weather and drought. Currently in Ireland, we only use harvested rainwater for non-potable uses such as washing clothes, toilet flushing and, most commonly, watering gardens. Still, these demands alone can account for upwards of 30% of our overall water use.
Although we think of ourselves as a water-rich country, there are areas with significant shortfalls, with Dublin and regions in the southeast increasingly seeing water restrictions. Even in the West, Inis Oírr in the Arann Islands requires regular expensive water shipments, and numerous other water sources across the region drop to low levels, especially during the Summer.
My previous research has shown that collecting rainwater in the wetter West of Ireland could meet more than 20% of a household's annual water consumption. In contrast, only approximately 10% could be supplied in the drier southeast, dropping to about 5% in the driest months. Although this seems low, it still equates to 17 litres of water per household daily and, of course, this impact is amplified by more people using these systems.
In addition to water supply, the benefits of rainwater harvesting in recent years have grown to include stormwater management. This means that we can capture and store rainfall in these tanks during storms to prevent surface water flooding and pollution from combined sewer overflow.
Combined sewers collect sewage (wastewater from homes, businesses, and industries) and stormwater runoff from streets, paths, and other surfaces in urban areas. They flow through the same pipes to wastewater treatment plants. Although not installed anymore, combined sewers are still common in older cities and urban areas.
However, the volume of water entering the combined sewer system can exceed its capacity during heavy rainfall. When this occurs, the excess water and untreated sewage may overflow from the system at designated points. In Ireland, sewer network modelling has estimated that cumulative annual overflow volumes were in the order of 5 to 10% of the total annual combined flows. This is particularly problematic in coastal areas where discharges enter the sea and interfere with local activities such as water sports, potentially causing not only damage to the ecosystem, but also a health hazard.
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From RTÉ Radio 1's Morning Ireland, Colman O'Sullivan reports on the use of rainwater in homes and businesses to help water supplies during droughts
Another problem associated with intense rainfall is surface water (pluvial) flooding, which occurs when the amount of rainfall exceeds the capacity of the drainage network. This type of flooding is driven in particular by short, intense rain storms, such as those that occurred over the Dublin area in October 2011.
Hull in the UK regularly suffers from this type of flooding. As part of my research there, we proposed a community-orientated programme where residents could be asked to empty a domestic raintank manually before rainfall, thus creating a space to store water. Fitting tanks was found to not only reduce flood risk but involving the community contributes to helping residents feel empowered and able to take action in relation to flooding, something which they previously felt powerless over.
In our current Sustainable Shared Spaces project, we've been exploring how to integrate rainwater harvesting features into our public areas. For instance, we're looking at innovative approaches such as concealing water storage beneath benches or within planters. This enhances water management, fosters social interaction and promotes biodiversity.
To make these systems work, we have to go beyond traditional methods, such as using standard black tanks. Instead, it's crucial to tailor the design to meet the specific needs and desires of communities. By incorporating environmental solutions such as biodiversity and water storage into social spaces, we can establish a new norm in urban landscapes where these features are expected and commonplace rather than rare exceptions. This approach ensures that sustainability becomes an integral part of our everyday surroundings, benefiting both people and the environment alike.
While Ireland may not be experiencing climate change as drastically as some other regions, we're certainly witnessing shifts in our rainfall patterns, including longer periods of drought and more intense storms. Rainwater harvesting can help to tackle these challenges. While it's not a substitute for large-scale water management infrastructure, it presents a cost-effective mitigation measure that also encourages public involvement in water conservation efforts. As we brace for a future marked by both drought and floods, everyone has a role to play in water management.
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Dr Ruth Quinn is an Assistant Lecturer in Civil, Environmental and Water Engineering at ATU Sligo. She is currently working on the SFI-funded Sustainable Shared Spaces project examining how to improve water management, biodiversity and social connectivity in our public spaces.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
