The ins and outs of water use in Kenyan cultivation

It is a common misconception that a great deal of water is wasted in the African floriculture sector. Is this true, or is the picture more nuanced? In this article, Royal FloraHolland explains how growers around Lake Naivasha in Kenya manage their water.

How much water do Kenyan growers use?
Joost Zuurbier does the maths: his roses need an average of around 5 litres of water per square metre per day, whilst natural rainfall is 2 litres per square metre per day. “Efficient water use is therefore not only an essential part of our commitment to sustainability, but also of our cultivation,” says the owner of Bilashaka Flowers, the rose nursery he has been running alongside Lake Naivasha with his sister Rosaline since 2001.

© Royal FloraHolland

Water is also needed for Marginpar’s flowers. The company grows 100 varieties of summer flowers at 14 nurseries/farms across four East African countries, half of which are in Kenya. The Kariki Naivasha nursery/farm is also situated close to Lake Naivasha. This lake, some 70 kilometres north-west of the capital, Nairobi, is a freshwater lake. Many other bodies of water in this region are salty or alkaline. This makes Lake Naivasha an important natural resource for flora, fauna and, to some extent, the floriculture sector as well.

Where does the water used by Kenyan growers come from?
Growers cannot pump water endlessly from Lake Naivasha and the surrounding aquifers. In the 1990s and early 2000s, the situation was quite different. The floriculture sector was growing rapidly; faster than the issuance of licences, monitoring and enforcement could keep up with. Between 1998 and 2009, the water level fell by as much as four metres. Researchers concluded that this was due to the growth of the floriculture sector, combined with extreme drought, population growth, small-scale agriculture, climate variability and geothermal activity. Since then, the water level has risen significantly, even reaching its highest level since 1940. Water extraction is now strictly licensed and closely monitored.

Growers around Lake Naivasha collaborate through the Lake Naivasha Growers Group to safeguard the water level and quality. In addition, they use innovative solutions to keep the water they use as clean as possible. Almost all growers also collect rainwater, which is stored in large reservoirs. Most have innovative recirculation systems in place, which allow water to be reused. However, as rainfall is not evenly distributed throughout the year, many growers also rely on the lake as a source.

Groundwater is also used. At Bilashaka Flowers, for example, it is used for seed production. For roses, the groundwater is too salty. Marginpar Kariki Naivasha extracts groundwater via three boreholes. “All water extraction from boreholes remains strictly within the limits set by the local water authorities and the applicable legislation,” says Steve Muchangi, ESG Manager at Marginpar.

How do Kenyan growers reuse water?
Water is reused as much as possible. Many growers make use of constructed wetlands for this purpose. These are natural filtration systems that utilise plants, bacteria and micro-organisms. These systems purify the water to a standard at which it can be reused in cultivation. This reduces both waste and the pressure on natural resources, and contributes towards a largely circular water system.

At Marginpar, it takes 48 days for wastewater from outdoor cultivation to pass through the entire system. The water is purified in stages through a natural process. First, bacteria in charcoal-filled tanks break down organic matter, after which the water is oxygenated via basins and a small waterfall. Papyrus reeds and water lilies then remove any remaining chemicals and fertiliser, whilst UV radiation from the sun disinfects the surface water.

In the pond at the end of the wetlands, Marginpar checks whether the water has been properly purified. “If the fish and frogs thrive and reproduce here, we can be 100 per cent certain that our wastewater is completely free of crop protection products. We also, of course, take water samples and test them against NEMA (National Environment Management Authority) standards,” says Steve. The treated water is pumped straight back into the fields’ irrigation system. Alternatively, it is used to water the large vegetable gardens for the nursery staff. Any additional fresh water required by the nursery/farm is supplemented by collected rainwater and the regulated pumping licence.

Bilashaka Flowers minimises its use of water from the lake by growing rose bushes in bags fitted with drainage channels, which (partly) collect the water not absorbed by the plants. This collected water is channelled to the drainage collection system, where it is filtered and purified before being reused. In addition, Zuurbier’s roses are grown on pumice rather than in open ground. The substrate acts like a sponge, says Zuurbier. “It retains moisture and fertilisers much more effectively around the roots, meaning hardly any water seeps away into the subsoil. Excess water can then be recirculated.”

What is the impact on the environment?
Not a single drop flows back from the nurseries into Lake Naivasha. Water used during cultivation is collected, treated and reused at many farms. In this way, growers are working towards a water system that is as circular as possible and are reducing their water consumption.

In addition, wetlands ensure that no grey wastewater enters the mainstream water system. Virtually all growers monitor their water consumption, for example using probes that measure the moisture content in the soil. In this way, Marginpar succeeded in reducing water consumption at the Kariki Naivasha nursery/farm by 28 per cent.

At Bilashaka Flowers, the limited amount of greywater released after use is collected in a rainwater basin. There, it mixes with rainwater and is reused for irrigation. Drainage water from substrate cultivation is also stored separately and reused.

“Although the lake’s water level is high at present, it remains a sensitive area and we are doing everything we can to protect it,” concludes Zuurbier, whose company has also been making a significant contribution to the drinking water supply in the neighbouring village for twenty years. Through the Lake Naivasha Growers Group, growers collaborate using a traffic-light system. In the event of extreme drought or other circumstances, the traffic light may switch to amber or red. In that case, everyone must restrict their water use. The traffic light has been on green for years, partly because all growers try to use as little water as possible.