Coramup Creek protection and paddock drainage
Paddy and Sharon Barber, Gibson
Paddy and Sharon Barber moved to their farm on the Coramup Creek near Gibson in 1994. The land was first released for agriculture in the early 1960s and when the Barbers took over the land it was fully developed and the creek had been grazed by stock since it was first cleared. The Coramup Creek and one of its tributaries runs through the property on its way to the Warden Lakes system near Esperance. The creek is the approximate boundary for the transitional zone between mallee vegetation to the east and sand plain vegetation to the west. There are no permanent pools on either the creek or tributary and the water moves through fairly quickly after rain.
Since they moved in the Barbers have been working to protect the creek by fencing and planting trees. They have also carried out some earthworks to drain their paddocks to alleviate waterlogging problems.
When Paddy moved on to the farm the creekline was mostly bare of native vegetation due to stock grazing as only one side had been fenced. "It was all pretty shocking, it was actually bare because there hadn't been much regrowth".
Parts of the farm suffer from waterlogging and encroaching salinity and Paddy says, "In a wet year up to 50% of our arable land would be affected by waterlogging, with substantial damage on 20%. Normally we would have 10% affected by waterlogging every year. I think we also get affected by waterlogging that we don't see. The waterlogged areas are getting bigger and bigger. When I first bought the farm I was still growing crops through the depression areas. It has got worse in the last three years and we've had a couple of wet winters and two summer rains which have also made it worse".
Fencing off parts of the Coramup Creek has kept Paddy busy over the last few years and he is also going to fence off the low areas close to the creek and plant trees there. He fenced off a wide area about 50-70 metres wide adjacent to the creek as the ground was very rocky and ruined his cropping machinery. The areas to be planted were ripped first and he found that the best results were obtained when he made his own ripper that was solid enough to be able to cope with the rocky substrate. He has tried planting yate trees on two occasions in the low-lying areas but has lost them both times and now believes that he will have to find more salt tolerant species to plant there.
Paddy has been alleviating the waterlogging problem by constructing grader banks to drain the water from the paddocks and into the creekline. "I had quite a big flat area and I knew I was going to lose it anyhow. You're not really making any money on it so you can just take it out completely and tree it and forget about it or you try and reclaim it and keep your main farming practises, which is what I'm trying to do here". The drains were constructed in January 1999 using a laser level and scraper machine. "The Ag. Department actually recommended 'W' drains but I got talked out of it because you really can't drive over a 'W' drain, whereas with these flat bottomed drains you can still get from A to B. The drain finishes a few metres from the creek. It has natural slope so we didn't worry about putting a batter on it. Because it really can only go there its not going to spread out and I still have good access along the creek". Paddy has decided that he won't put any crop in at the lower end of the drains but will keep it grassed over to stabilise the soil.
Some of the soil that was taken out of the drain was put onto the depressions as Paddy had noticed that a few areas in one of the paddocks were becoming soggy, although there were no signs of encroaching salinity. He is not sure yet how successful filling in the low areas has been. Paddy is hoping that the drains will grass over which will help to stabilise them. However the drains do not have a sandy base so he believes that they won't erode much at all. He doesn't want to fence them off or plant trees next to them as this would make it difficult to maintain them in the future.
Piezometers have been recently installed across the farm to monitor the water table. "I don't have much of a problem down at the front, it's only this low localised area but hopefully I'll alleviate that".
The Outcomes and Observations
Paddy is pleased to see that after fencing four years ago the paperbarks and acacia have started to regenerate along the creekline. He has noticed however that weeds can be a problem. "Any areas that you fence off, if you've got existing radish or barb grass, it becomes a big problem. Lovegrass is also a problem, at least when it was unfenced with grazing it didn't take a hold. So this is a bit of a concern as I doubt whether the natural species are really going to get established if the weeds really take a hold". He is now thinking of ways to control the weeds in the riparian corridor.
Part of the creek was fenced and grazing had been excluded before Paddy bought the farm. He has noticed a big difference in the density and health of the native vegetation between the fenced and unfenced areas. Samphire has been a recent coloniser of the creekline on the property as Paddy says that it wasn't growing on the creek when he first moved there. "I've noticed that some of the mallee trees were looking quite thin, now they've got regrowth at the base of them and they're starting to come back again".
It is too early to tell how successful the drains will be at alleviating the waterlogging in the paddocks, but early indications are looking promising. Paddy would like to put in more drains but says, "I ran out of money doing the drains. I would have liked to have filled all the little low areas in, so I'll have to come back and do them at a later stage. I also wanted to spread more clay and hopefully hold some of the water back as well. I'm lucky that it was natural drainage so it made it easier".