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Water conservation and innovative solutions to a water crisis
Water conservation
and innovative solutions to a water crisis
Climate change, overpopulation, water pollution, urban encroachment, species extinction – our planet is facing a number of potentially devastating environmental threats which impact us directly.
Samanta Stelli
South Africa is a naturally water-scarce region, with unevenly distributed seasonal rainfall. Climate change is exacerbating these weather patterns, with hotter and drier summers, water shortages, and an increase in extreme weather events such as floods and droughts. Basically, the ‘drys’ are expected to get drier, and the ‘wets’, wetter. Water is expected to become even more of a limited resource than it already is.
It is essential that all business, industries, economic sectors, and the public in general start adapting their lifestyles to adopt a more water wise way of life.
Landscapers and gardeners have already started adapting to water restrictions by implementing water wise landscaping principles in the way of rainwater harvesting tanks, filtered ‘grey water' (water from washing machines, dishwashers, baths and showers), and water efficient irrigation systems.
Grey water can effectively be filtered for reuse by including constructed wetlands as part of the landscape.
Stormwater runoff and rainwater harvesting
We are seeing an increase in floods across the country and this is having serious effects on the environment and infrastructure. Hard and impermeable surfaces prevent water infiltration into the ground and can result in flash floods.
Using permeable surfaces in a landscape or garden can effectively reduce the impact of heavy volumes of stormwater. When designing a landscape, take note of the topography of the area, as well as the type of soil present.
Compacted, clay soils increase run-off, while loamy and sandy soils are better at absorbing water. Loamy soils are best as the rich organic content of these soils hold water around plant roots. Adding mulch, compost and retention granules also increases the permeability and infiltration capacity of soil. Infiltration and percolation of rainwater through soil provides a beneficial role in filtering rainwater and preventing debris and pollutants from entering ground water, acting as a natural process of water purification.
Run-off, especially in urban areas, can introduce contaminants such as oil, detergents, solvents, dead leaves, pesticides, fertiliser, and bacteria from pet waste in rivers, dams, and oceans.
Rainwater harvesting simply refers to the collection, storage and distribution of rainwater from your roof or other impermeable surfaces. It’s easy – your roof and gutter system provides a perfect collection point for rainwater; all you need to do is direct it to where you want it.
Rainwater harvesting has many benefits
By collecting, storing and using rainwater, there is less strain on the municipal water supply, as well as a reduction in your municipal water bill. Any flooding, erosion, and pollution that may be caused by stormwater runoff is reduced.
Also, rainwater contains minerals and nutrients that can give you a more productive and healthy landscape. Gutters can be used to direct rainwater to storage containers, rain tanks or specific areas in your landscape.
How much water can you save by harvesting rainfall? Remember that every 1m² of roof generates 1 litre of water from 1mm of rainfall. So, if you receive 20mm of rainfall on a roof of 100m², this will generate 2 000 litres of water – for free.
Water efficient irrigation – drip systems
Drip irrigation is widely understood to be the most water efficient irrigation system available. It is a watering system that delivers water either on the surface of the soil, or directly to a plant’s root zone (sub-surface). Drip irrigation systems are water wise for the following reasons: • Evaporation is minimal as water is not sprayed, but water application is still efficient and effective. • Application of water can be directed to specific areas precisely and effectively, as opposed to spray systems that apply water to a wider area and end up spraying non-watering areas of the rooftop and wasting water. • Drip systems save between 30-50% water compared to spray or sprinkler systems. • There is no compromise on plant health; in fact, there is often a reduction in fungal plant diseases as leaves are kept dry. • Healthy plant root systems are encouraged as water is applied directly to the roots. • Can address complex site issues such as wind (especially for rooftop gardens), differing microclimates, damp, drainage, and run-off due to the efficient and accurate positioning of the system. • Can be used indoors in atriums and greenhouses, as well as outdoors.
When using a drip irrigation system, it is essential that the water be filtered before use especially if any form of grey water is being used. Failure to do so will result in excess clogging of drippers even if they are the 'self-cleaning' type.
Rooftop gardens and green roofs have been around for decades, especially in highly populated urban areas such as cities and towns. Initially, rooftop gardens were used mainly to provide insulation in cold northern hemisphere climates.
These days, with limited ‘green’ space, rooftops gardens are used to reduce the heat island effect in cities reduce stormwater run-off and flash floods, create small safe havens for insects and birds, and beautify the environment. In essence, this is a creative and functional way of reducing reliance on municipal water, saving water, and preventing pollution.
Rooftop gardens can be as simple as a few container plants artfully arranged in an open space, or as complex as a fully waterproofed and vegetated roof surface. In a rapidly growing urban environment with limited space, many people are choosing to live in flats, apartments, and townhouses.
A rooftop garden or landscape is ideal for those living in homes without gardens. They make use of unused or underused space and are great for plants and veggies that require full sun. Veggies such as tomatoes, cucumbers, peppers, peas and beans, tall corn and rambling squashes, carrots, radishes, beets, kohlrabi, fennel, potatoes, and onions are ideal for rooftop food gardens (but may require some protection from the wind in some areas).
If you are looking more at an aesthetic landscape, consider hardy, sun-loving water wise plants such as indigenous Highveld grasses and succulents (hydro zoned appropriately); think of plants such as Dietes grandiflora (iris), Tulbaghia violacea (wild garlic), Agapanthus praecox, Plectranthus neochilus, Carpobrotus edulis (vygie), Aloe marlothii (mountain aloe), Drimiopsis maculata (leopard lily), and the well-known Chlorophytum comosum (hen and chicken).
Remember that there are a number of factors to consider when implementing a rooftop garden or landscape: • Make sure your structure/building/roof can support the load of a rooftop garden (engineering requirements will apply). Using lightweight planting materials such as vermiculite, perlite, and sphagnum moss alleviates the problem of weight, and absorb and hold water well. • Rooftop environmental conditions such as full sun and strong wind can be tough on plants. If necessary, provide shading for more delicate plants, and buffers (for users and plants) to prevent excessively windy conditions. • Speak to an expert if you are interested in implementing a fully planted green roof. You may need to consult with a structural engineer or architect to conduct a structural analysis of your building. • A simpler, more cost-effective solution is to use containers and raised plant beds. Lightweight containers are ideal as they are portable, flexible in use, and affordable. You can really get creative and can easily change the design as required. Back to water wise irrigation – luckily, drip irrigation is great for rooftop gardens and landscapes. Because of the tough environment, rooftop gardens often require daily watering. However, they are also susceptible to water loss.
Drip irrigation can prevent water loss to evaporation, while efficiently providing the correct amount of water to plant roots. To further reduce your water usage, consider directing harvested rainwater to your rooftop garden. Remember to place rubber mats, wooden pallets, or other material to buffer the containers or planters from the roof to allow for more efficient drainage and to protect roofing materials and structure.
There are so many ways to save on your municipal bill by capitalising on free water. By harvesting rainwater, using mulch, and using water efficient irrigation systems such as drip irrigation, you can dramatically reduce your reliance on potable water, especially in landscapes and gardens. Rooftop gardens are water-saving, creative, innovative, space-saving solutions to a limit in garden and landscape space. ■
For more information on water conservation principles in gardens and landscapes, contact Samanta Stelli at sstelli@randwater.co.za or +27 (0)11 724 9371.
Sources: 1. Reinders, F.B., Grové, B., Benadé, N., van der Stoep, I. and van
Niekerk, A.S. (2012). Technical Aspects and Cost Estimating
Procedures of Surface and Subsurface Drip Irrigation Systems
Volume 1: Main Report (WRC Report No. TT 524/12); Volume 2:
A Manual for irrigation designers (WRC Report No. TT 525/12); and Volume 3: A Manual for irrigation farmers (WRC Report No. TT 526/12). 2. https://lifestyle.co.za/rooftop-gardens/ 3. https://www.sahomeowner.co.za/rooftop-garden-basics/ 4. https://www.thespruce.com/rooftop-gardening-1403340 5. https://www.bbg.org/gardening/article/start_a_rooftop_ container_garden 6. https://www.waterbrothers.co.za/rooftop-gardens/
