Treating floods and droughts with the same medicine
On a recent trip to the UK, I was alerted to the fact that the topic of soils is high on the agenda of environmentalists there. I was visiting various entities involved in river restoration, catchment sensitive farming, and the catchment based approach, and everywhere I went, the topic of soil health was on the lips of my hosts.
The reason for this, is that the UK has been hit by considerable flooding in recent years, and they are fast learning to replace measures such as mechanical dredging, with what they term NFM (Natural Flood Management). The concept is one in which you use the Ecological Infrastructure to protect you from floods instead of, or in support of the “grey infrastructure” (steel and concrete). So they build leaky dams, reconnect rivers with floodplains etc etc. But top of that list, and most widespread, was talk of improving soils, and more specifically their ability to hold onto water for longer, instead of letting go of it as fast as the rain falls upon it.
Now , with me having worded the sentence above as I have, it is probably dawning on you, as it did on me, how managing floods and managing drought, might have overlapping solutions. Keeping rainwater back in the catchment for longer, and stopping it from all rushing away at once, will minimise flood affects and drought affects. Here in SA, we have those 5 or so long dry months in winter, in which our rivers slow to a trickle. End of winter trickle is known as “base flow”. Just as the Poms want to keep water out of the coffee shops along the river Ouse in York, so we would like the rivers to flow stronger through August and September to support all the ecosystems that rely on those rivers (humans not excluded).
And having spongy deep soils that hold onto water achieves both.
The River Ouse in York
Site of considerable flooding
The uMngeni River in September
after long dry months
Studies show that soil with high organic matter levels and good structure, holds more water. In other words, a seldom burnt (not never) , never ploughed, piece of land in the berg, covered in thick natural grass, supplies us with more consistent river feed than a ploughed maize field where the trash is burnt every year.
These two are extremes….the berg and the maize field….. but more commonly the answer lies in subtleties of management in a vast area of grazed and burnt veld landscape. Farmers have the challenge of trying to maximise the tonnage of grass for their cows, while preserving a diversity of species, while keeping costs down and income up. Certain grazing and burning practices favour less palatable species. Other practices can result in poor basal cover (a lower number of plants per ha, which leaves bare ground between), and still more nuanced techniques give higher grass yield in wet years, or maybe in dry years, but probably not both. Farming neighbours are often dismissive of one another’s techniques. Fire regulations impose boundaries to what one can do, and every valley is different. Scientists from the varsity have vast research based knowledge. Farmers have vast local knowledge. National magazines can publish articles on best practice that are controversial, and not nationally applicable.
So what is best practice for drought and flood management?
The answer probably lies in area specific study groups, where scientists and farmers work together to establish their own unique best practice, for widest possible adoption in their own valley. The chances are, that despite the fact that we have farmed this land for over a hundred years, there will be some experimentation too.
Some reading matter on the topic: