Siltation of Gwayi-Shangani dam threatens agriculture expansion in Lupane

/SILTATION of Gwayi-Shangani Dam is threatening agriculture expansion at Arda Jotsholo in Lupane District as water harvesting measures are being undermined.

A visit last week to the Arda Jotsholo weir built in the 1970s, showed that the dam is heavily silted, creating a false impression of a full dam following heavy rains in the country. According to Arda board chairman Mr Basil Nyabadza, the problem is also affecting the estate's winter crop with an immediate solution needed before viability is threatened.

Mr Nyabadza said plans to expand the estate from 600 hectares of cleared land to the 1 400 hectares of arable land available have been deferred due to siltation at the weir.

"Siltation is a threat to expanded agriculture. The opening up of additional land will have to be deferred until we manage this problem. We can do our summer planting but to attain the necessary economies of scale, we need both the winter cropping season and summer season, that way we then retain our better yields and profitability will come into play," he said.

Mr Nyabadza said initial plans were to clear 700 hectares but that can only be done after securing sufficient water to enable cropping. He said as a temporary measure, four boreholes have been drilled at the estate to augment the water supply as the target is to plant at least 500 hectares of winter wheat.

"Water harvesting is a critical element in our agriculture. Winter crops are only possible when we have harvested our water and the boreholes are only a temporary measure. In the summer, we need to start building a second weir to improve water retention," he said.

Mr Nyabadza could, however, not disclose how much is needed to desilt the dam or build a new weir saying the authority is yet to be informed by the water engineers. He said at the moment plans are to salvage enough water for the 300 to 400 hectares of cropping from the weir.

Estate manager Mr Ndodana Ncube said the existing weir which was built in the 1970s to harness water for Arda Jotsholo was meant to last 25 years.

"It has since surpassed that period so as a result we are witnessing high levels of siltation at this weir. We are now unable to irrigate the targeted 500 hectares as the water source is no longer reliable," said Mr Ncube.

Mr Ncube said the solution was to build a second weir and redirect piping and power systems at the same time using the original weir as a sand trap.

Mr Nyabadza said although the country might not have the funds for such projects, there were people with money looking for investment in the agriculture sector hence the importance of enticing them to take up these long term investments for the benefit of Zimbabwe's food security attainment.

Meanwhile, the summer maize crop at Arda Jotsholo whose plant population is between 50 000 and 60 000 plants per hectare has been described as a success despite attacks by the fall armyworm. The expected yield is nine tonnes per hectare and part of the crop is under the Command Agriculture Programme.

Mr Ncube said the estate has managed to contain the armyworm through the use of various chemicals and that the rains played a part in minimising the scheme's irrigation system expenditure outlay. Arda Jotsholo is under a mobile irrigation system.