This probably sounds more than a bit daft; after all, it is August and record-breaking high temperatures are forecast for the Algarve, and other Mediterranean regions in Europe – but this is the time to plan ahead. We are now past the summer solstice and the days will soon feel shorter and, we hope, cooler nights might bring some dew. The welcome relief of the first autumn rains cannot be far away.
For those of us with no automatic irrigation systems (and no automatic high water bills!), using the free rain water that does come to us is a subject of great interest. The challenge is to make use of the intermittent and sometimes violent showers by planning to capture, store and use the water in our gardens and on our land.
Many houses in the Algarve are not built with gutters or with tanks or cisternas to store runoff water. This is an enormous waste of a very precious resource. There are many water-saving strategies that are cheap and easy to build into a new house, including using a settling tank and overflow for the water, which falls onto any roof or hard-standing areas. For houses far away from any mains water, a cisterna fed by runoff rain water is essential but may need topping up in the long hot summer months by buying in water.
If we concentrate on saving water for irrigation rather than human consumption then life becomes much simpler. Gutters and downpipes directed into a closed holding tank or cisterna can provide weeks of water for a fruit and vegetable patch, and good quality water it is too. This can be especially valuable for anyone pulling salt-contaminated water out of a coastal borehole or well.
Bioretention is a simple way of retaining water inside gardens and land areas and can stop harmful erosion by storm water runoff. Looking at the areas where water runs or gathers naturally is the first step, shallow depressions of differing shapes can be enlarged, or even created, and used to hold water so that it infiltrates slowly and naturally, thus helping to establish nearby trees and shrubs. Excess water will drain into the soil rather than running off, taking fertile soil layers with it, and causing damaging erosion on slopes.
In urban areas where land is at a premium, the use of green roofs can also capture rain and greatly reduce runoff. The specially selected plants will take advantage of water when it is available and will survive long months with no water at all.
A long-term project at Lisbon University is showing which plants can be used to create green-roof structures in hot dry climates. Other advantages are the insulating qualities of the plants for the building. This is another way of reducing needless use of energy for air conditioning or heating as the building does not reach excessive high or low temperatures. A good example of this in the Algarve is the green roof on the new hotel rooms at the Estoi Palace Pousada, but there are other examples. A Portuguese specialist company has built these structures on domestic, commercial and industrial buildings, and they also look stunning!
Large tourist complexes, urban developments and hotels have an opportunity to save money and create beautiful landscape and garden features by recycling waste water as well as capturing rain water. The aim of bioretention is twofold: it allows the reduction of impervious surface areas (so often a contentious part of planning applications) and it allows soils to naturally store and filter storm water and avoid erosion.
The fact that managing rain water can also significantly increase the visual beauty of any site is particularly important. Creating green spaces and shady corners that last through the year has got to be worth considering.
By Rosie Peddle
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Mediterranean Gardening Association – Portugal