Our efforts to develop a sustainable irrigation system at Matapila passed through several iterations. An important baseline we developed was we needed to supply 75 gallons of water per day per "square" for adequate vegetable growth (a "square" is our terminology for a 30 meter x 30 meter plot). Considering that a reasonably sized garden of 6 "squares" (about 1/6 acre) requires 300 gallons of watering per day, a better system was needed. Our greatest concern of supplying irrigation water from a village borehole, as demand was increased with garden expansion, was the risk of compromising the drinking water supply. We decided the only viable solution was to drill a second borehole dedicated to irrigation, and in 2015 LCPC raised funds (approx 10,000 USD) to do so.
Upon completion of the borehole, Jonathan Hunter conducted a dynamic pumping test at 13.6 gpm for 90 minutes, concluding a dynamic water level (drawdown) to 11.4 meters, from a static water level at 8.8 meters . Recovery was observed withing 10 minutes.
Our pump was installed at 30 meters with an allowable flowrate for the borehole of up to 12 gpm (0.75 L/s).
In September 2015, we retained Jonathan Hunter (then Managing Director of Drinkwell International Ltd) to conduct a geophysical study at MOH's Matapila site to
- performance test existing borehole
- indentify a suitable drilling site for a new borehole & manage drilling and completion
Our objective was not only adequate capacity, but also ensuring the new well would be hydraulically independent of the existing well.
The resultant borehole was successful, drilled to 42 meters and completed with 40mm PVC casing. A static water level at 8.8 meters below the surface was measured
We purchased two 5000 liter (1320 gal) polyethylene tanks in Lilongwe, and had a brick platform constructed to elevate them 2 meters above ground level.
The Matapila layout presented a challenge. While the new borehole is directly adjacent to the garden fields, the solar power generation panels sit atop the main center building, 100 meters away. We mounted the storage tanks between the two, but uphill, effectively forming a triangle. A "well house" was build to house and protect the well head, and electrical connections.
We selected a Grundfos downhole pump for quality and reliability. Flowrate is determined by the power supplied: i.e. the more solar panels, the higher the flowrate. The model chosen will deliver 8 GPM against a resistance of 50 meters while drawing 475 watts of power. (see pump curves below)
Our plan was to pump water from the borehole to storage tanks during the day, and then irrigate either in the evening, or at the same time during the day that the tanks are filling. This avoids significant complication and expense of using batteries for pumping.
Four 125 watt 24 vDC solar panels were added to power the well pump, paired in series to generate up to 500 watts of power at 48 vDC. Higher voltage is needed to minimize voltage drop in the long distance from panels to pump.
Fittings had to be added to the tanks . . . thankfully team member Peter is slim, and a good sport!
In Malawi, there are 5 “effective” hours per day of full intensity sunshine, in which time the pump, running at 8 gpm, can provide 2400 gallons from the borehole to the tanks, filling them both. This is sufficient volume to irrigate 32 “squares”, or approximately ½ acre. . . plenty of room for garden expansion!
A controller turns off the borehole pump when the storage tanks are full, to prevent overflowing.
Irrigation and Agriculture
Piping and wiring was run underground.
In 2017 our team added piping and irrigation tubing to bring the operating squares number at Matapila to 5. Further expansion is planned for 2018!
In 2018 we were excited to recently learn that a new borehole was completed at Chimwang'ombe, and that MOH would like for it to be used as an irrigation water source. The garden at that center, once seemingly hopeless, has been dramatically improved by compost generation and advanced farming techniques over the past few years by Gladys, the director at that center, and could very much profit from drip irrigation. We requested that the old 1ooo L tank, now no longer needed at Matapila, be moved to Chimwang'ombe and we will initiate a first generation system there.