16 minute read
Lessons for a changing climate
Al Ittihad Park under The Palm Monorail showcases native plant species over ten hectares. Photography by Alessandro Merati © Cracknell
There is much to learn from arid regions to ensure that natural resources are adequately conserved. Three case studies from Dubai illustrate approaches to irrigation, planting and parks in the Middle East.
As the climate emergency intensifies, conserving natural resources has become an urgent priority. In terms of public parks, managing our water resources wisely through responsible and efficient irrigation, coupled with improved planting media and selection of place-appropriate and locally available plants, plays a critical role in resilience for longterm sustainable maintenance and reduction of water consumption. By utilising responsible water conservation and horticultural strategies, we can effectively maintain the vibrant green spaces parks provide while reducing their impact on water demand and increasing their contribution to local sense of place.
In the UK, where it sometimes seems like it never stops raining and supply of water is something we can take for granted, there is less available fresh water than many realise. In 2021, Environment Agency Chair Emma Howard Boyd said: ‘If we continue to operate as usual, by 2050 the amount of water available in England could be reduced by 10 to 15 percent, some rivers could have between 50 and 80 percent less water during the summer and we will not be able to meet the demands of people, industry and agriculture.’
There are nearly 200,000 hectares of parks and green spaces in the UK. With changes in rainfall and evaporation we need to think carefully about our use of water in parks and choice of planting with regard to water demand. These might seem considerations that until recently only belonged in regions like the Middle East, where rain in Dubai can be only 13cm a year and temperatures can reach 48 degrees Celsius, but this is changing and there is much to learn from these arid regions to ensure that natural resources are adequately conserved.
There is much to learn from these arid regions to ensure that natural resources are adequately conserved.
Our work in the Middle East has taught us at Cracknell much about sustainable irrigation and planting strategies, and we have developed a thorough understanding of resilient, efficient and adaptable techniques.
Irrigation
Responsible irrigation practices conserve water and energy, reduce soil erosion and pollution, and improve plant health. Smart irrigation systems use technology to monitor soil moisture, wind speed and other factors, enabling operators to optimise irrigation programmes to further reduce water consumption.
With depleting available fresh water, exploring alternatives such as rainwater harvesting, recycled water (treated effluent/grey water) and condensate water has become ever more important. Here are some methods we have used.
The power of drip irrigation systems: Unlike traditional sprinkler systems that disperse water over a wide area, these systems target specific plant root zones in a park, reducing water waste from run-off and evaporation.
Harnessing weather-based irrigation controllers and soil moisture sensors – the tech for precise watering: These devices adjust watering schedules based on local weather conditions and soil moisture content, preventing overwatering on rainy days, or underwatering on hot ones. This smart approach ensures that parks are only watered when needed.
Organic mulching – a simple yet effective tool: Mulch retains water in the soil by reducing evaporation and ensuring that plants have a consistent water supply, thereby limiting the frequency and amount of water needed. Mulching also suppresses weeds and regulates soil temperature. Recycled material weed-control barriers can also help in reducing evaporation, cutting out light and nutrients to unwanted weeds that compete with the desired plants.
Soil moisture retention additives can also be used to reduce the percolation rate within the soil. These additives can be sourced from natural materials/minerals such as volcanic tuffs, perlite and Cocopeat. Mulching and retention additives also improve the soil structure of sandy soils and reduce fertiliser use through leaching prevention.
Rainwater harvesting: nature’s answer to irrigation needs:
Rainwater collection systems can be used to gather and store rain from rooftops and other surfaces in irrigation storage tanks, thus reducing reliance on municipal water supply. Where possible, water can be harvested by installing a sub-surface drainage system from which the water can be treated and fed back into the irrigation network.
Using grey water – a second life for used water: If local regulations permit, consider using grey water (lightly used water from sinks, showers, etc.) for irrigation. This practice not only conserves water, but also reduces the strain on sewage treatment systems. Grey water is not commonly used in the UK at all and there’s a perception that it may be less safe than mains or borehole water, but we are starting to investigate its use more as the climate crisis worsens, and this should be encouraged.
In the Middle East, use of grey water for irrigation of public parks, streetscapes and major developments is normal. In Dubai, the quality of treated grey water is very good and there is a separate network of Treated Sewage Effluent (TSE) lines supplying treated water for irrigation. Many parks have their own storage tanks supplied from this Municipal TSE network. The water recovered from sewage is ploughed back into greening the cities rather than discharged into the sea. Treated water also benefits plant health, as it carries minimal amounts of nutrients such as nitrogen. Where practical, reed bed filtration systems can be used to treat grey water without using energy, while also creating wetland areas attracting birds for nesting sites.
Implement a water budget: A water budget can help parks stay on track with their water conservation goals by setting a limit on the amount of water to be used for irrigation. This strategy requires careful planning and monitoring of water use. In the MENA (Middle East & North Africa) region the Municipality’s sustainability guidelines, such as ESTIDAMA in Abu Dhabi, set water budgets that must not be exceeded; for instance, public open spaces with less than 70% hardscape cover, i.e. most parks, must not use more than 4.5 litre/m² water in a day.
Practice seasonal adjustments: Adjust watering practices based on seasonal changes, watering less in cooler months when plants are often in a dormant phase and more in warmer, drier months when water demand increases. Daily timing adjustments are also important. Irrigating during early morning or late at night in the summer minimises evaporation losses and allows efficient percolation. It is good to irrigate in short but frequent ‘bursts’ to minimise wastage and evaporation.
Windbreaks and shade structures – lowering evaporation rates: Windbreaks and shade structures can help reduce the rate of evaporation, allowing plants to retain more moisture. They can also provide aesthetic and functional benefits to parks, offering shaded areas for visitors.
In the Middle East, use of grey water for irrigation of public parks, streetscapes and major developments is normal.
Capillary breaks to avoid saline ground water: Summer temperatures compound problems with saline ground water in the Middle East. High temperatures draw water to the surface leaving salt on the soil surface. If left to build up it disturbs the soil pH and prevents plant roots from taking up nutrients. To mitigate this, a capillary break is introduced under tree/palm pits to prevent saline water ingress.
Eliminate need for transportation of water: The use of many of the techniques here, such as rainwater harvesting, mulching, shade and selection of native water-wise planting, should eliminate the need for any transportation of water.
Routine maintenance – preventing water waste and Legionella growth: Even the most advanced irrigation system can waste water if it’s not well maintained. Regular inspections are vital to identify leaks, clogs, or other malfunctions, enabling timely repairs. A well-maintained irrigation system ensures efficient water use for a longer period. There should be a strategy for Legionella prevention by avoiding stagnant water at any point in the system. It’s advisable for the maintenance contractor to include in the O&M Manual a Legionella Management Plan based on the design drawings.
Specifying and sourcing native plants has the added benefit of improving ecological value by supporting native insect, bird and animal populations.
Horticulture
The skills involved in water-wise plant palette selection and native plant cultivation are a vital component of tackling climate change and the sustainability challenges of water shortages. Responsible horticultural practices to be used in public open spaces include:
Xeriscaping: Choose native, preferably local, adaptive droughttolerant plants that need less water and fewer nutrients to thrive. By opting for these species, parks can maintain biodiversity while reducing both their water footprint and requirements for fertilisers. Xerotropic plants possess unique adaptations, such as deep root systems and water-storing tissues, enabling them to survive in arid conditions, to withstand prolonged periods of drought and so reduce water consumption significantly. It’s also important to mitigate the effects of high mortality rates during the summer months in hot climates by choosing salt-tolerant species. Specifying and sourcing native plants has the added benefit of improving ecological value by supporting native insect, bird and animal populations.
Hydrozoning – a strategic approach to plant placement: Group plants with similar water needs together to minimise over- or under-watering. This practice ensures that each section of the park receives the right amount of water, promoting plant health.
Nutrients – providing for growth in a poor planting medium: Desert sand is inherently devoid of plantaccessible nutrients; hence the planting medium must be amended to provide the plants with nutrition for growth. Planting medium is a homogeneous mixture of desert/ agricultural planting soil, organic fertiliser/compost and inorganic slow release/compound fertilisers, including a soil moisture retention additive to improve the water-holding capacity, allowing water to be retained in the root zone for release at the plant’s wilting point.
Compost helps mobilise the existing soil nutrients so that good growth is achieved with lower nutrient densities. By supplying humus and nutrients, biodiversity and long-term soil productivity is improved. The addition of compost also improves soil texture and the ability to retain moisture. An inorganic slow-release fertiliser is recommended to provide a steady supply of nutrients over a longer period of time, without waste through leaching.
Minimising transportation of materials: Minimising importation of planting materials and avoiding long transportation saves time and costs. Compost sourced in the UAE is generally local cow manure, heat treated and sterilised. Alternatively, it is sourced locally through green waste and meat meal from local abattoirs.
When developing green space in coastal environments, the existing soil is full of accumulated salt. The planting medium to be used is then sourced from the interior of Dubai where the inland ‘sweet soil’ (agricultural soil) is fit for planting. Other than manufactured fertiliser tablets, all plant nutrition is sourced regionally.
Implementing water-efficient irrigation practices in public parks is a relatively small but important aspect of tackling the climate emergency. Landscape architects have a vital role globally in influencing developers and local authorities alike in the merits of water-wise schemes and place sensitive native planting. The role of public awareness and education should not be underestimated: signage, interpretation and events programmes can teach visitors about water conservation, why it’s essential and what they can do to help by adopting water-saving practices in their homes and communities. By employing these strategies, parks can continue to provide beautiful, green spaces for communities to enjoy, contributing to health and wellbeing, while making a tangible contribution to global water conservation efforts.
Case Studies
Zabeel Park
Zabeel Park in Dubai provides a nearly 50-hectare oasis of relaxing shaded green space, popular with the whole community. An integrated smart irrigation network optimised water usage by using weather-based sensors to analyse local climate patterns and adjust irrigation schedules accordingly. By avoiding overwatering and minimising evaporation, the park achieved a 60% reduction in water consumption compared to a non-smart system. The smart network also enabled remote monitoring and control, allowing park authorities to fine-tune irrigation settings in real time and provide necessary nutrients via a chemical injection system. The 2005 project not only conserved water resources, but also demonstrated the feasibility of employing technology driven solutions for sustainable landscaping practices in comparable parks. The plant selection strategy focused on incorporating a combination of visually appealing native and xerotropic species well suited to Dubai’s climate, providing an ecologically balanced, biodiverse and resilient landscape.
A key to ensuring landscape sustainability was to select plants with a low water requirement.
Al Ittihad Park
Al Ittihad Park in Dubai exemplifies a sustainable approach to landscaping by utilising more than 60 indigenous tree and plant species across 10 hectares, including Prosopis cineraria, Ziziphus spina-christi, Adenium obesum, Jasminum sambac, Typha domingensis and Moringa peregrina These native species showcase the distinctive beauty and resilience of the local flora, while minimising water requirements and maintenance demands, promoting biodiversity.
On inception in 2012, a continually updated list of native plants from which to expand, maintain and replace dead specimens was drawn up and continues to be used today. Postcontract management on site was vital to ensure adherence to the species lists and to see that contractors didn’t default to easier-to-source tropical species. Continued pressure on local nursery suppliers has helped to maintain a healthy stock and supply of native species regionally, and to build a consensus among nursery growers that native plants are a viable and more sustainable option.
Museum of the Future
This 2022 2-hectare resilient park landscape is actually the skin of the museum buildings – a berm and roof garden with a topographical profile not normally seen in urban Dubai. Working with slopes steeper than 60 degrees required innovative design solutions to suspend a soil ‘carpet’, as standard landscape techniques for soil retention could not be used. Green wall technology together with a recycled material geocell system retain and stabilise the slopes, in conjunction with specialised in-line drip irrigation systems using grey/treated sewage water. All of these elements are contained within an engineered ‘sandwich’ that clothes the mound in its xerotropic living green carpet. Cocopeat (bio-product) and lightweight perlite improve the water-holding capacity of the planting medium and create a light soil that helps to limit the structural loads.
A key to ensuring landscape sustainability was to select plants with a low water requirement, and to design smart irrigation systems that would automatically manage the water application based on moisture content data received from soil moisture sensors and weather information from a local weather station. The steeply sloping nature of the mound elicited concerns about rapid loss of irrigation water from run-off from the root zone.
To counteract this, water is delivered in short frequent ‘bursts’ to minimise wastage and evaporation, and subsurface geocells allow excess irrigation and storm water to be harvested and recycled. This ensures it isn’t released into the urban drainage system. Water usage under this system was reduced by 25-30%, substantially improving on the original KPIs (key performance indicators).
One of the primary plants used for the mound was a variety of fleshy sea-purslane – Sesuvium portulacastrum – commonly found by the Middle Eastern coast. Quick growing, tolerant of heat/salt and requiring minimal irrigation, they are the ideal plant to ‘green’ the ‘mound’ in a sustainable way. Native trees used include ghaf (Prosopis cineraria), Ziziphus spina-christi (sidr) and acacias, perfectly adapted to local environmental conditions and requiring minimal water and fertiliser to sustain them. Their masses of nectar-rich flowers support native bees, and seasonal fruits attract wild bird populations. Further ecological value is brought by the native grasses and ground covers such as Cenchrus ciliaris, Zygophyllum qatarense and Sporobolus spicatus, which are supremely adapted to poor saline soils and are self-propagating; their seeds sustain local birds such as hoopoes, sparrows, sunbirds and white-eared bulbuls.
Colleen D’Souza is Director and Head of Cracknell’s Integrated Horticulture Team. She has been instrumental in expanding the plant typologies used in the MENA regions over the last 30 years, challenging local standards and adding ecological and resilience value.
Mohan Baporikar is a Director of Cracknell’s Integrated Irrigation Team. He is an ardent enthusiast for the implementation of efficient and sustainable design practice within irrigation and MEP works, learned from over 30 years of designing, executing and maintaining many types of irrigation, drainage and water feature projects largely in the MENA region.
