The Function Of Water - Water Harvesting
The first concept regarding the function of water in a garden is water harvesting. Basically this is the act of collecting water from rain; remember rain does not always fall straight down. One of the best ways to catch as much water as possible is through, big tall trees with lots of foliage. This follows the principle of the bigger the service area the more water you can catch. Although life is never that cut and dry, and that statement comes with different nuances; for example, not everyone wants, or can have big trees in their garden. If the tree is big with lots of foliage, in certain circumstances, this could actually be counter productive, by the way it could actually block a lot of rain, and divert it away from the desired area.
The best way to utilise this type of harvesting, if it suits your garden, is to have those particulate types of trees located not in gardens, but on the borders of a gardens; in particular, gardens that do not receive enough water and could use a good old drenching when ever it rains.
For example if the garden you desire to harvest water for is on a slope or hill, it would be good to have these type of thick foliage trees on the higher side of the incline, relative to the garden. This way, the runoff rain water from the tree hits the ground just above the garden; so the water can run through the top soil of the surrounding ground, along to the garden, and gently water its roots.
One point to pay attention to, is to make sure the run off won’t be too strong and erode the garden and the surrounding soil. Of course this will be up to you to gauge, as every situation is different, but here are a few things that can be done to help prevent this from happening.
First making sure the distance from the trees and the garden is sufficient and correct. Second making sure the surface soil has grass or some type of rooting ground cover to provide it with enough structural integrity. And third, making sure the top soil isn’t too dense or loose, which will cause erosion or excess runoff. Personally I would recommend grass in the area between the tree and the garden if possible.
A good way to test if the distance is right, is to run a hose on the ground at the point wear the foliage of the tree ends. Let the hose run at full and watch how the water behaves; does it sink straight into the ground without becoming saturated, if so, that means you can have the garden quite close to the tree edge. If the water sinks straight into the ground and slowly becomes saturated, you know you need to have the garden a little further away. If the water saturates the ground very quickly or runs straight off, you need to place the garden further away; in this case I would do one of two things or even both if possible: either change the topsoil to something more porous, or create a rubble drain underneath the top soil. I would recommend doing the two in combination for best results, but either one will be sure to help.
Rubble drains are one of my favourite ways to distribute water and I will explain them in detail later on. Another option that can be quite rewarding in many ways, although it uses more work than most people are willing to take, is to let the run off from the tree fall into a pond and irrigate the garden through tiny creeks or brooks.
Not everyone likes or wants trees in their garden, for what ever reason, and this is understandable, as everyone is different, with different needs and wants, as well as other restrictions. Personal, I love to utilise trees, they are one of my favourite type of plants, and these days you see less and less of them. I like to use them right in the centre of a garden when ever I can. This is for various reasons; but for the purpose of this blog, I will explain why having them in the centre of the garden is great for harvesting water.
Like I stated previously, one of the best ways to harvest rain is through big trees with lots of foliage. But this can be limiting and even counter productive in certain circumstances; such as having your tree in the centre of the garden, which limits what you can plant underneath the shade of the foliage. As well as becoming some what restricted to planting outside the perimeter of the foliage of the tree, to gain enough sunlight and rain.
That being said, Having a tree with lots of dense foliage in the centre of your garden can also work quite well, if that is what you desire. If you do choose this route, keep in mind what you plant on the edge of the perimeter of the foliage, because runoff from the trees can damage more delicate plants, such as flowers.
There are many ways you can make the dense foliage trees in the centre of a garden work quite well, but I will leave that topic for a later blog. For now we will look at another way to utilise these bigger trees and how some of the down sides such as thick foliage diverting the water in an adverse way can be remedied.
Choosing the right tree is first and foremost, that is something you have more control over; of course, like most situations, there are many types of trees that can work well for this, and I encourage you to research this your self, I will also be discussing it in depth later on, but to keep it simple for this blog, the tree should have the following characteristics.
Firstly, it is not an aggressive grower. What I mean by this is, when pruned, the tree sends out lots of new shoots all over the place, quite quickly, as opposed to two or three shoots. These types of trees also tend to put out suckers at the base or trunk of the tree, and I would avoid these trees for this purpose.
Secondly, the tree should have lots of small feathery plumes of leaves that tend to grow and feather more at the ends of the branches, rather than all over the branches; a good “extreme” example of this type of foliage would be a gumtree.
Thirdly, the tree should have fewer but thicker branches in proportion to its trunk, as apposed to branches which are thinner in proportion to the trunk that has lots of suckers or skinnier branches and lots of run of branches with dense leaves; a good “extreme” example of this would be those trees and shrubs that hedge well.
Next is thinning out of the branches in certain locations on the tree, as to let in light, rain and air where desired. I like to imagine this as arms reaching from the main stem of the tree; and all the little fingers at the end of the beaches collecting the rain, and directing it to the centre of the tree.
Before you do this though, it is important that you know how to prune correctly; this is a big mistake that a lot of people make, and can damage the tree long term, if not done correctly. I suggest learning the correct techniques before starting this step. I love pruning, it is one of my favourite aspects of gardening and I have a lot of information to share regarding this later on.
Once you know how to prune correctly, you should look at the tree you are going to thin and visualise how you want the tree to be, to achieve your goal. As our goal is to catch maximum rain water, and let in enough light and air, you want to not deviate too much from the basic natural shape of the tree. You also want to focus on keeping the majority of the foliage to the outer 30 percent of each branch.
Once you have a visual image in your mind, of how the tree should look, get rid of any dead branches, or branches that grow in towards the tree centre of the tree; you also want to keep the shape nice so the branches don’t cross each other and they all aim out in an even way. Keep in mind the analogy of the arms and fingers. A good indicator is the aesthetics of the tree, if it looks fairly neat and even, chances are you have done a good job. Just imagine how the rain and light will enter, remembering the sun moves, and rain doesn’t always fall straight down.
If you are unsure, or this is new to you, just take it slow, bit by bit; you can even take just one branch a day or even once a week. I wouldn’t recommend taking off more than 70 percent of the tree, this can shock the tree too much; if you have to do this then you may be using the wrong type of tree. I would assess the tree every six months to see if a tidy up is required. Regular pruning is recommended, generally once a year is a good idea.
Water harvesting with trees can be quite interesting and highly rewarding. Just keep these principles in mind; how can I catch a maximum amount of water, and safely divert it to the desired location. Your mind is a wonderful thing, give it that information, some time and focus, and you will work wonders.
The last concept to harvesting water is more work on your part and it involves more labour and it kind of delves into the landscaping side of gardening. It involves altering the terrain, or if you are savvy and industrious enough, you can build the garden around the terrain it self. This of course will come down to your level of experience and knowledge. If you are going to go down that route, make sure you know what you are doing, as this is a huge topic in and of its self, which I will be discussing a lot as we go on; that is for sure. But if you would like to look at this in the interim, I would suggest you look at how to utilise hills and valleys, soil density and make up, various sorts of drainage such as rubble drains, ponds and streams, and even stones and stonewalls.
My favourite way to alter terrain for water harvesting, is through a combination of rubble drains covered in top soil and grass. The method is quite simple, it does take a little man power though, and the method can be modified in many various ways, depending on how far you want to take it. Even if you are able to utilise this method in the most simple way, when you see the results in action, it is a very satisfying experience, indeed.
Before I leave you to contemplate these things, I will first give you a quick overview of a basic rubble drain. You will need some sort of safe rubble, such as rocks, old bricks, cement, or broken pots, anything really, as long as it is safe, durable and can support the ground above, while at the same time allowing water to flow through the cracks. The rubble drain can be used for many reasons, but for the purpose of harvesting it is best used in an area that receives a substantial amount of water. You can tell this by seeing what parts of the ground become saturated first when it rains. Places to look for are low lying areas which tend to pool easy, corners of structures or walls, on the parameters of trees, and anywhere a lot of water runs off. Also areas where the soil is very dry or has high clay content, places that don’t have grass or very little naturally tend to be this way.
Now that you have your location, you need to figure out where you wish to divert the water to, or away from. This will be determined by the size of the area you are working in. The bigger the distance from point A to B the more work, and rubble is required. The rest is quite basic, you want to create a pathway for the water to travel from the high water volume area to the low water volume area. Dig a shallow trench from one point to the other at the same depth. This will be up to you to decide how deep, depending on the amount of water that hits the area; you should be able to get an idea of this by watching when it rains or using the hose on the location of where the drain will be placed. Now starting from the place where you wish to harvest the water from, you need to modify the shallow trench by digging out and creating a slight decline in the direction of the desired location where you want the water to flow. A good rule of thumb is to make the the final destination of the drain as deep as the roots of the tree or garden will be.
Once you have this looking good, and the path for the water to flow is a shallow trench with a decline that progressively gets slightly deeper from one end to the other, so by utilising gravity to allow the rain water to follow the trench from the rainfall area, to the area in need of water; all you have left to do is compact the bottom of the trench with your foot or hands, increasing the trenches efficiency and minimising loss of water. Then evenly fill the drain with the rubble; leaving at least 30cm from the top, then fill the rest with the soil you dug from the whole if it is suitable. If the soils clay content is too high you may want to add sand or modify the soil. When filling the trench with soil, it is best to over fill, to allow for the soil to settle and some initial run off into the drain. The best thing to do is put grass back over the top of the soil or some kind of ground cover or low shrubs. Use your imagination; it just needs to hold the soil in place and prevent erosion.
If this blog was able to spark your interest in the concept of water harvesting, get out there and get your hands dirty, and you will find out how rewarding it can be, or at the very least look into these ideas more your self. And if this all seems too overwhelming, don’t worry it really is quite simple, if you know what you are doing. I will go into these concepts individually in depth in other blogs, so stay tuned.