Veld reclamation

     These are worrying times for Zimbabwe. Last week, Bulawayo,  Harare and elsewhere were in turmoil with protests over the economic situation in the Country, but at Sinamatella we were cut off from the rest of the world by the government's shutdown of the internet combined with a two-day power failure. This is not meant to be a political or current affairs blog so I won't comment further on the events of the week away from Sinamatella except to hope that there will be a happy ending to this very long-running story. What that happy ending might be is anybody's guess but let's hope that it is better than the one we thought we had reached in November 2017 - which turns out to have been neither happy, nor the end.

   So, the week at Sinamatella. Over the years that we have lived here we have noticed (we think) a steady increase in the amount of bare, eroded ground we can see as we look out over the park from the top of the hill.  Rainwater rushing over the surface has caused sheet erosion which continues every rainy season........

And the depth of the soil loss is shown by the exposed roots on this old Mopane stump.....

    We have no measurements to show that the bare areas are increasing but even if they are not, they are still a worry. We put a lot of effort into providing water for the animals but that is of no value if they don't also have food. This isn't a new idea - the Parks Authority staff worked on veld reclamation right into the 90's but nothing has been done since then so we decided that this should be the year that we start again, trying to do something about the situation.

   Towards the end of last year, the Hwange Conservation Society (UK) very kindly agreed to fund an experimental piece of veld reclamation that we can replicate on a larger scale if it is a success. We chose a piece of land close to Sinamatella that has been heavily affected by sheet erosion but is easily accessible for the necessary work and for monitoring afterwards. Most of it looks like this.....

But our aim is to get it looking like this piece of land, only a couple of hundred meters away.........

   I know, from speaking to some of the people involved in reclamation in the past, that they relied mainly on laying down brush lines (that's lines of cut bush that provide shade and protection from grazers for delicate grass seedlings). Professor Google and good old-fashioned books I've looked at suggest that breaking up the soil crust is also important and we know that works from having seen the effect of laying pipelines under bare ground for game water - the disturbed soil quickly becomes well covered with vegetation. So, we decided to try out a variety of methods....1. brush lines alone, 2. breaking up the soil in lines with a ripper then covering with brush and 3. breaking the soil but not laying brush lines. And so, to work.

    First, cutting brush. It would be a bit counter-productive to destroy useful vegetation in an experiment on encouraging vegetation so we cut the brush where it isn't wanted - along the edges of the Sinamatella airstrip. The airstrip isn't much used. The last time a plane landed was in September 2017 so the strip......

And the airport buildings (departure lounge, customs and immigration, duty-free shop - that sort of thing )........

....... are a bit neglected.

 We loaded the cut brush into our old Land Cruiser (affectionately known as 'Granny')........

While the tractor was doing the heavy work, ripping the soil at the experimental plot......

Then we laid out the brush lines....

.....and thought we had finished.

   It all looked very neat and we were rather proud of it. I suppose that was the mistake because a couple of hours later a heavy storm with very strong winds swept across the whole thing and scattered our neat brush lines as if they were made of paper. That's what experimenting is about of course - you learn by testing out ideas and clearly, unsupported brush lines are an idea that doesn't work. Faced with either having to add a lot more brush to make it all much heavier or pegging the lines down with rough stakes, we decided on the stakes and that has now been done.  From here we have to monitor the success or otherwise of the various plans and then decide if we want to scale the programme up before next rainy season. No doubt I'll have more to say on this in the next few months.

Mandavu Dam Wall

     If I had made any New Year's resolutions (I didn't) I might well have resolved to post to this blog on a regular basis and I would already be close to breaking my resolution. That's entirely normal of course but... I would have an excuse (and a real one at that!) For some time after we got back from our Christmas break, we were without a reliable internet connection. Eventually we discovered that the problem was not some arcane bit of IT or satellite programming that had gone wrong but something we could solve fairly easily - the mounting for the satellite dish was coming away from the wall and putting the dish out of alignment. I fixed it back up and it seems to be OK now, so here goes......

   Mandavu Dam.

    Fourteen kilometers from Sinamatella is the biggest body of open water in Hwange National Park - Mandavu Dam. It's a hugely productive dam, thanks to the nutrients introduced by the hippos and the hundreds of buffalo, elephants and others that drink there in the dry season so it is popular with anglers who are allowed to fish there at weekends. It's also a vital part of Sinamatella's game water supplies, and an important breeding and feeding place for numerous birds.

 

 We pass the dam regularly and often spend time there counting and listing birds but until recently we had never given a thought to the maintenance of the actual dam wall. I'm certain we wouldn't have thought of it now if Colin Gillies from Wildlife and Environment Zimbabwe hadn't e-mailed me with some concerns over the state of the wall. I knew about as much about dam wall maintenance as I do about computers (i.e. next to nothing) so I asked my good friend Professor Google for help. He, of course, knows more or less everything, and as I read through various websites that he suggested, I became more and more concerned.

   The first thing I was sure we needed to worry about was trees. Apparently, trees on an earth dam are a disaster waiting to happen. Mandavu didn't have trees - it had a forest........

   The road across the wall - dam to the left, forest to the right!

   Next concern was termites and animal burrows. We have both of those all over Sinamatella so probably at Mandavu too but had anyone ever checked? Almost certainly not.

  Prof Google guided me to one website that gave a series of stages to look for to show any deterioration in a dam wall. First stage, in which there is nothing to worry about,  is a flow of clear water on the downstream side and the final stage, probably best labelled 'panic',  is a whirlpool in the dam itself and a strong flow of muddy water and debris downstream. As far as I could see, at that stage all you can do is 1. Run for your life and 2. Call the emergency services. I was pretty sure that we were far from that situation but not at all sure of anything else so Courage Mutema, the Sinamatella Parks Ecologist and myself went out to have a look.

   It was, as you would expect, a mixture of good news and bad news. The good news was that there was a small flow of clear water through the wall, there were no active termite nests (though there were some large ant nests) and no obvious animal burrows. The bad news items were that the wall was covered in trees, that many of the rocks which are meant to resist wave action (the technical term seems to be rip-rap) were out of place and that the road across the wall has eroded, causing rain water to pour down the back face of the wall where it has cut some fairly disturbing gullies.

Part of one of the gullies - not something you want to see in a dam wall!

   The gullies were obviously something we should be dealing with very soon so we started work on them first. A proper solution to the problem will mean rebuilding the top of the wall to direct rainwater into the rip-rap but that will take some organising. For now, we have simply thrown tons of rock and brush into the deepest gullies and we'll try to cover them over with soil so that grass can grow and bind it all together. It would have been nice to have heavy earthmoving equipment to do this but that's way beyond our resources. Instead, we have manpower, and of course a Land Rover ....

   Removing the trees turned out to be a huge task. If they had been Mopane, as they would have been in most parts of Sinamatella, it would have been difficult enough but in fact they were mostly Acacia tortilis, which comes armed with both hooked and straight thorns..........

   ..........and strongly objects to being handled. It took us two full days to fell all the trees, cut them into reasonably sized pieces, winch them up to the top of the wall and stack them. By the end we were all heavily scratched and thoroughly fed up with the task but satisfied to have got it done. I will go and kill all the tree stumps with a strong alkali to stop re-growth and poison the ants whose nests seem to go deep into the wall. We will eventually re-build the eroded crest of the wall and spread the branches over it to protect the loose soil and encourage grass-growth. All being well, this is a lesson learnt and regular dam maintenance will become part of the annual work schedule at Sinamatella. We are grateful to Colin Gillies for pointing out what needed to be done - but I have to say, there were times as I pulled yet more hooked thorns out of my skin, when I wasn't quite so grateful!