Water Feature

Background

So, why a water feature, and what type of water feature.

In our previous houses we have always had water features as amongst other things they attract wildlife and are supposed to have a tranquil effect on people, so it made sense that the new Garden Railway would incorporate the water feature. Rather than just a pool of water, running water in the form of a stream was agreed upon.

After looking at lots of options, including many preformed streams, a liner running to a sump was decided as the way forward, partly due to cost (4 metres of preformed was very costly), but mainly due to not finding something that would fit into the railway.

Planning

As my railway is on two levels (passing over each other) the water was planned to flow from the high point to a sump at the lowest point (bottom right hand corner), no waterfalls were requested.

First step was to measure the length and width to determine the size of liner required, this was about 4 metres long and less than a metre at the widest point.  Second step is to work out the height for the lift for the pump, and the flow. Finally the sump size to hold the pump and sufficient water for the feature.

Purchase of Components

The butyl rubber liner I wanted only came in 2 metre widths, so a 5 metre length was purchased, to allow for any error or inaccuracies in the “rough” measurement.  Along with this I bought a fleece under liner designed for the rubber liner and to replace the requirement to line the water way with sand.

The pump was the next consideration, I decided that I would like built in filter and UV, this was so no chemicals would be required to keep the water clean and therefore good for wildlife, and after much research with approximate 1/2 metre lift height, a 500 litre/hour pump would be required, adding in spare capacity I went for 1100 litre/hours pump, which apparently is good for 2.3 metre head.

I already had a water tank to act as a sump, which was a 100 litre header tank that was unused when the house was converted to a combi-boiler.

At this point the only other items required were the pipes and clamp to connect the pump to the feature, however, please read on for developments

Implementation

Having roughly marked the route of my stream, I decided that I would fit the sump first, so a suitable hole was dug.

The sump was then fitted on a bed of soft sand.

The lid was fitted (to prevent debris getting in, and area was cleared.

Next the bed of the stream was dug out.  If was at this point, despite advice to the contrary, that I decided I needed a “top-fill” point (bottom right-hand photo) and a small “spill-way” with a pipe inlet was purchased, though it came with its own mesh filter, this has been discarded

Whilst digging the stream bed, I noticed the sump was not supported well in its hole, and used 450mm X 450mm paving slabs cut in half to provide support.

As both the rubber and fleece liners came in 2 metre widths and I needed less than 1 metre, confirmed after a “dry run” I decided that I would lay both as double thickness, and though this was fine for the fleece, probably a mistake for the rubber liner as this became difficult (but not impossible) to manage at double thickness, but I didn’t realise this until it was fitted.

The pump was switched on to check all was in order, and the water flowed as expected.

With the water flowing in the stream bed, this was my first real understanding hydrodynamics in this setting.

First I considered that 1100 litres/hour would give me a very good flow, but it breaks down to 18.33 litres/minute, or less than a third of a litre per second, and that is without the loss of flow from the lift.  I expected a wide stream that (without restriction) would be at least 25mm deep, as you can see from the photo its a lot less.

However, with the right restrictions is the right places a good looking flow can be achieved. So my stream banks are far deeper than the water requires, and the banks will be lowered.

It was at this stage the liners were cut to size, I considered that 50 – 75 mm from the water edge would be enough, it is but ONLY JUST, it is amazing how far water can wick (capillary action) up the side of a rubber liner.

The stream bed was laid, and temporary bridges were put in place to allow for the running of trains, what you will noticed is that the sump has changed.

What was wrong with the original sump

  • Due to the reinforcement at the bottom of the tank the pump would not sit at the bottom, reducing the useable height of water above.
  • Though approximately a 100 litre capacity, due to the flow of water, in hot and windy weather evaporation can be quite high, meaning more regular top-ups (every few days).

A new 200 litre purpose made sump was purchased, this allowed the pump to sit at the bottom of the sump, and depending on the weather 7 – 14 days between top-up (if there is no rain).

Next Steps

With the water feature in place and running 24/7 the next steps were to finesse the whole area to blend in with the garden.

A variety of of round pebbles and cobble were purchased, from 20 mm to 180 mm, again I miscalculated what I would need, due to not understanding the water dynamics, and I have 500 kg (1/2 ton) of large cobbles that I do not need.

So using the small pebbles in the bed and building out I have built up the bank.  This is still work in progress until I have the final bridges in place, and then will be able to blend everything in.

As a temporary measure, I used a couple of suitable sized rocks for supports, and some hard wood for the track support, as seen in the photo.  Though not ideal, this does mean the track can be re-laid and the trains can be run until I can replace these with more suitable bridges.  However inclement weather dictated the need to cover the wood to provide some protection.

The photo show the top of the stream and the lager sized rocks.  In the bed of the stream as can be seen I have used a pond product that is small gravel fixed to a rubber sheet, this goes on top of the liner and prevents it showing through, and gives a pleasing gravel bed effect.

Bridges

Bridges were sourced through Brunel Models, and were bespoke for this railway, I was looking to replace the temporary track bed and supporting pillars, but with hind sight should have though broader than this.  Below is one of the bridges as received.

The bridges have been fitted, again, temporally as I awaiting material for the transition from the bridge to the land.  Some adjustment was required to get the heights correct, and in turn the gradients either side of the bridges will need to be adjusted, as can be seen with the level and rule.

With the bridges in place and gradients adjusted again we can run trains.

So, as of July 2020, this is where we are with the water feature.  I am now awaiting delivery of the final items to transition the bridges, and adjust the gradients.  This will be updated when the parts arrive and work re-commences.

Update September 2020

The transition parts for the bridges arrived, using uPVC cloaking I added sides to these, fitted in position and the gradients adjusted for the new levels. 

At the same time the paving to the right was fixed in position, and paving added to the left of the feature.

As mentioned earlier, though I had a reasonable flow, I was never quite satisfied with it, my old pump had a flow of 1,100 l/h at 1 mtr head, so a new pump was bought that has 4250 l/h at 1 mtr head.

I was loosing water, more than considered from evaporation etc, I eventually traced this to water seep/weep as the water entered the sump, the sump not being as level as it could be though less than 5 mm across the length and width, and flow on to the sump being erratic.

As the pump was to be changed I decided to remove and re-level the sump, lower it by approximately 25 mm, add half paving slabs outside the sump to retain the earth, and using HDPE plastic supports to ensure the bank heights are transmitted over the sump for a consistent flow.

A small bridge has also been created for human transit to the paving and managing the garden to the right of the feature.

Currently most of the planned work for the feature except for a little work on the banks is now complete, but any changes will be highlighted here.