The Sunday News
Jonathan Maphenduka
MANY years ago, I was farming in the Mangwe District when I met a man who taught me how to build weirs without calling a water engineer and end up spending a lot money. My farm (all 2 610 hectares of it in this Region 5 district) had two rivers running through it.
There were two dams on the farm, two dip tanks and several water distribution tanks across the farm. The water tank near the homestead supplied water to the cattle pens, ensuring that the troughs were full when cattle were being handled. The homestead had a tower tank which was filled with water from a pumping station on the river two kilometres where three engines were used to abstract water from the riverbed.
This tank also supplied water to the dip tank near the homestead.
The two dams, one in the centre of the farm, were located three kilometres apart with the dam in the centre tending to dry up in bad rainy season. The second dip tank was six kilometres from the one near the homestead, while the second dip tank was approximately four kilometres from each of the two dams.
There was a water tank with troughs on the banks of the east bank of the river that was sand-abstracted to provide water for the cattle on what in fact was paddock five of the farm. The stretch of the river within the farm had no pools to provide water to the stock on the farm.
There was also another concrete tank with troughs near that dip tank six kilometres away from the homestead which was used to top up the dip tank and provide water for the herdsmen who lived in a compound nearby. This dip tank and labour compound were on paddock 11 and cattle had their water on paddock 14. We are now left with paddock six and seven and paddock eight and nine without reliable water sources, especially paddocks six and seven which had no source of water at all.
When I moved in I had enough money to stock the farm (thanks to the Cold Storage Commission’s cattle finance scheme which was available to farms then) and install pumping equipment and the tower water tank for the homestead. It was then that I started looking for suitable sites for a weir. Along Tshabakadzi River which passes through paddocks 8 and 9 I found my first site for a weir which became known as the Kariba.
The river passes over a granite rock across the riverbed which formed a fall over a sandy spread of riverbed, forming a pool below. Just before that fall, the riverbed spread across the entire width of the river. I had a man in my workforce who had been building weirs for local farmers with great success. He used a diamond-tipped chisel (njombolo) to drill holes across the riverbed at specified distances. The holes were 30 centimetres deep which he put deformed bars (that is the trade name of the product). Before pouring concrete around the steel bar, you put a screen across the steel bars.
The width of your intended wall must be two metres with shutters on both sides of the wall to hold your concrete. On average every farm has rouble (ukhethe) to mix with your river sand and cement. The only material you have to spend money on is cement and the deformed bars.
Quite often farmers use scrap wire instead of screen for reinforcement of your concrete.
The concrete is further reinforced by adding stone boulders to give your wall strength. So, at the end of the day you would have spent money on three essential items: cement, deformed bars and hiring shutters to hold your concrete.
When my wall on this site was done, I had a wall which slopped on one side to allow floodwaters to pass almost unhindered, with the rest of the wall rising to almost two metres, allowing floodwaters to shoot far beyond the limit to which the natural fall had created.
The result was the Kariba which my farm workers talked about. This was a pool of clean water which is necessary in cattle production. This great weir was, however, a precursor of failure when I chose for my next weir a site which turned out to be unsuitable and was swept away by floodwaters before my cattle had access to its reservoir.
The reader will remember that paddocks six and seven had no access to water and this required that cattle be driven to either the dam on paddock 11 or the one on paddock 10, which was the most unreliable dam on the farm apart from being dirty and muddy which is a source of the killer liver fluke disease during the dry season. I had to do something to find water for the two paddocks.
I found what I thought was a perfect site on a branch of that river where we relied on sand abstraction which provided water for the homestead and the cattle on paddock five. This stretch of river had no pools to water livestock. The site had a little hill on one side and riverbed had a gentle rise on the opposite bank. The bedrock across the river, however, was all sandstone and, while it was easy to drill holes for your deformed bars, it was not suitable even for a small weir which I built there. When the floodwaters came the sandstone bedrock just gave in and there was a big bang as the wall gave way.
That was the end of that site, although the deformed bars remained unmoved from the concrete wall to this day. On the whole this was a highly developed farm which had been grazed for many years. The farms in Mangwe have a different history from the land reform programme.
Next week I will narrate the story of success and failure of my farming experience on that farm.
