Water harvesting on Northland hills

In a normal summer Carlos’s  property would be much greener than the browning hills neighbouring him. While this has been nothing like a normal summer, Carlos’s property has luxuriant growth that his neighbours just can’t match.

He purchased the property in 2013. It is on a windswept ridge exposed to biting south-westerlies. The property has a silica pan that plant roots find very difficult to penetrate, quickly suffering from a lack of water when the dry weather comes.

Originally from Western Australia, Carlos brought permaculture skills with him as pioneered by his countryman Bill Mollison. He started building swales, shallow ditches that run along the contour lines. On the upper side, they tend to slope down towards the deepest point,  and the earth excavated is used to create a bank on the downward side, retaining the water that flows in.

Figure 1: A larger swale showing open water and water hyacinths (apologies for the finger over the lens)

Over time Carlos has created Swales across the whole property at about 10 m intervals.  Some are wide as the above, and where the contour is gentler, they tend to be narrower, perhaps 60cm or so.

Figure 2: A narrower swale. Note that there is still a generous bank on the lower side. 

The swales have been developed over the last decade so some of them haven’t been in that long. But the results are impressive. Trees all over the property are thriving – some better than others, and there’s been a lot of trial and error. But as the ground has become better hydrated, plants have become more vigorous and the work done to disrupt the pan and retain water is paying off big time.

These puriri show the benefit of hydrated soil. When Carlos arrived he could look over the top of them and they were struggling. I’ve rarely seen puriri with such dense and healthy growth.

Figure 3: Carlos by a stand of puriri.

Fast-growing exotic trees have created a framework for the property and are now accompanied by a huge variety of fruit trees and vines. The larger trees will provide a variety of timbers. Eventually, the property will be mostly closed canopy with light wells for some of the smaller fruit trees. The system can also be adapted for livestock.

Carlos trusts nature to get the soil dynamics right. He has a deep appreciation of the importance of the soil biome and uses any branches and vegetative waste to feed and foster the fungal population.

Figure 4: Carlos on a bridge over one of the narrower swales

Kikuyu is ever-present. At first glance it seems to be competing heavily with the young trees, but Carlos points to a “galaxy of life” that thrives in the moist environment under the lush kikuyu.

He is also aware of the cooling impact of the trees in the environment and has an area of vines on the northwest side of his house that cools the air that is drawn inside. 

As I write this, large areas near Cape Reinga are on fire. Carlos has demonstrated how harvesting water with swales can re-hydrate a landscape making it more resilient to fire, drought, and flood. The contoured swales keep the water in the land from close to the top of ridges.

Perhaps if we identified landscapes most at risk from fire we could pilot a project to begin large-scale harvesting of water? Perhaps we could join the global Ecosystem Restoration Communities movement and get people and machines on the land harvesting water? Carlos is showing how it can be done.

What do you think?