News and knowhow for farmers

Water reservoirs enable farmers earn a premium and halve production costs

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By George Munene
By constructing water reservoirs farmers are able to save on watering costs as well as avoid reliance on rain-fed agriculture—allowing them to produce over the drier seasons when most agricultural produce is scarce and commodity prices are at their peak.
Timothy Mburu constructed his 50 million liter capacity dam on half an acre in 2011. It was 2015 before he first sowed on his five-acre farm at Naro Moru, Nyeri County. Having not to rely on tap water and channeling water into his farm through gravity, he has cut his production costs by up to 60 per cent. For his cabbages for example, his watering costs per acre is just Sh 3000—constituting largely of labour. This is compared to the other farmers around him who spend Sh15,000-20000 on irrigation. “I do not cultivate crops over the rainy season—I target my cultivation over the drier June to September months— that way my produce hits market when the supply is lower than demand,” says Mburu.
The dam also doubles up as a fish pond, hosting tilapia and catfish which he sells for an extra income.
“As a career agriculturalist trained in crop production and water resource management, I had an acute understanding of how important it was before anything else, being that farming is a water-intensive undertaking, that I have a reliable source of water. My dam ensures I have clean water for both crop irrigation (cabbages, potatoes and garlics) as well as watering my animals (15 cows and 20 sheep) throughout the year.” he says.

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For Caleb Karuga having a water pan on his farm was a no-brainer. In 2010 he had been having major water problems and farming on leased land, he could not sink a borehole or well. On his farm at Kikuyu sub-county, he’s set up a 144,000 liters pond; a do it yourself project that cost him Sh43,000—Sh20,000 in labor costs and an addition Sh23,000 in buying a dam liner. “I would have had to buy 14 plastic tanks with 10,000 liter capacity at a cost of Sh980,000 to harvest the same amount of water. I tap water from my goat shed and gutters on my chicken coop which is all fed into the reservoir. The pond has made me an unwitting fish and bee farmer besides keeping my farm irrigated for three to four months, “he explains.
It has also created his own magical oasis, a cyclic ecosystem that begins with the rainwater wash off deposited from the goat’s shed full of nitrogenous waste. To this, he adds chicken manure to provide the perfect fish breeding ground. He is also now got into duck rearing—they also provide manure, spurring phytoplankton growth giving his fish even more food. This ‘improved rainwater’ provides readymade liquid manure for his vegetables, lucerne for his goats, sweet potato vines, strawberries and maize. He is now even able to ‘zero graze’ his own bees which have a readily available water source meaning they do not have to wander.
To construct his dam Mburu spent Sh1.2 million—an exorbitant amount given that when he built it in 2011 dams were still a novel idea for most farmers; resource mobilization in terms of getting a government-owned excavator to his site took him almost a month and cost him Sh12,000 to run every hour. With an eight hour workshift the project was completed in 26 days. “Today you can hire the same machinery at half the cost and with the proliferation of private companies offering excavator services you do not have to spend the Sh100,000 I did just to get the bulldozer and its personnel to my farm, “he points out.

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On another five acres he recently acquired, he’s worked to construct a 110 000 liter water pan on an eighth of an acre. With his worn experience this has cost him just Sh20,000 in hired labor. He is working on progressively increasing it to sit on half an acre, with a 20-30 million liter water holding capacity.
His 50 million liter dam sits on half an acre but the water consumes just ¼ of this with the rests constituting compacted walls. The walls are four meters high above the ground with a slanted depth of three meters—this is done to reduce the wall pressure to prevent the dam from bursting. At the top of his walls, he grows tough grass such as Kikuyu which spreads by producing a thick mat or thatch above the soil surface which improves compatibility preventing soil erosion. Trees should not be grown on the dam’s walls as their roots will crack into the dam’s walls to sip water.
A water reservoir should be set up out of the direct site of running water and the impact of onrushing water reduced by putting up detours that reduce the velocity of onrushing water.
Mburu does not control for evaporation; “Not once have I ever run out of water—50 million liters can irrigate a 10-acre farm for 90 days— the germination time for most crops— if some 100,000 liters is lost through evaporation, that is negligible,” he says.
Caleb urges Kenyan farmers to consider water harvesting as essential to crop production and not just as a way of tapping water for human and animal consumption.

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