With climate change making warm weather and drought conditions more likely, sustainable water use is becoming ever more important. Heat warms soils and when it does rain evaporation is increased.
Sustainable water use is about balancing the use of water with the availability of water sources, while reducing the need to take water from the environment. One way of utilising water in a domestic garden would involve collecting rainwater during the wetter months, with one of the simplest ways being to install a water butt to utilise runoff from roofs and sheds, then using the water collected efficiently with the aim of minimising the amount of waste water.
Using grey water can be used as a sustainable short term water source during extremely dry spells. Because of pollutants such as soaps and detergents in these water sources, long term use can negatively affect plants' health and it should not be used on edibles or potted plants. Bath water typically contains the least pollutants compared to dishwater or washing machine water. Grey water should be used immediately because of colonisation of harmful bacteria from food or skin particles typically found in these sources.
Retaining water within soils can be achieved in a number of ways. Keeping the height of a lawn to approximately 10cm during hot weather reduces ground temperatures and subsequently evaporation. It also reduces plant stress allowing the grass to develop a deeper root system.
Mulching is another effective way of retaining water within the soil while also reducing water logging during heavy rainfall. Mulching reduces evaporation from the soil while also suppressing water thirsty weeds. The mulching material is less important, as long as a sufficient layer is used, although biodegradable materials also have the added benefit of slowly releasing nutrients to the soil. Mulching should be applied to bare soil when the surface is warm and moist, ideally in the autumn. This locks in water and prevents water thirsty winter weeds from establishing.
For potted plants larger containers are much better at retaining water. For smaller gardens where larger containers may not be viable you can add water absorbent granules to retain water. Plastic free biodegradable granules are just as effective and widely available.
When establishing new plants it is important to follow the water requirements. These are often stated on the labels or can easily be looked up online. Watering plants too frequently, especially during establishment, encourages shallower root systems and will hinder the plants resilience to drought conditions in the future. Not being watered too frequently encourages plants to establish deeper roots and become more self-sufficient.
If watering is necessary, timing is important. Watering during dawn and dusk when the air is cooler will reduce evaporation and allow the water to penetrate the soil. Watering should target the roots of the plant and you should avoid watering dry tolerant plants.
Landscaping techniques and choice of plants are just as important as efficient water use. Creating hydrozones within the garden involves grouping plants with similar water requirements in different areas. This allows you to target watering to plants that need it and not overwater plants that don't need as much. Creating an arid zone with drought tolerant plants is a great place to start. Strategically planting taller shrubs to cast shade over water thirsty plants in the evening can reduce soil evaporation.
For more information on some local initiatives and creating a water wise garden here are some useful links.
RHS Waterwise Garden: Sustain Your Garden Through Drought and Flood by Tom Massey
Tom Massey - The water wise garden
https://www.watersencam.co.uk/
