12 April 1996

Tap reservoirs

waiting below

Sinking a bore-hole can significantly reduce a farms water bill. Andy Collings reports

"WATER, water everywhere nor any a drop to drink." So said Coleridges Ancient Mariner but, ironically, the same is almost true for land-locked farmers.

Not far beneath the feet of most farmers is a vast reservoir of water. If tapped for on-farm use, water bills can be reduced significantly – and yes, properly treated, unlike the poor mariners plight, it can be used for drinking.

Water purchased from water authorities is not cheap – a farm running a 200-cow dairy herd with followers for example, can expect to use in the region of 2.2m gallons a year. This runs up a bill well in excess of £10,000.

The solution could be to abstract water from a bore hole. Horsham-based Marner (UK), a company specialising in such matters, believes water bills could be slashed by as much as 95% by using abstracted water, with a pay-back on investment of just 2/3 years.

Sounds good so far, but what does having an on-farm bore hole entail?

Marner managing director, Chris Martin reckons to set up about 20 bore holes a year, not just into agriculture but to a whole range of industries requiring large volumes of water.

"The first thing is to identify just how much water is required and for what it is to be used for," he explains. "Water volume dictates the size of the bore hole and the type of pumps and pipes to be fitted; the use designation – washing down, drinking etc means the treatment plant can be geared to suit."

Next stage is to have a hydrogeological survey made to discover just how deep a hole needs to be drilled to reach water. Mr Martin draws on the use of a computer programme to tell him the make-up of ground strata for any given area. The aim is to drill into a chalk aquifer band where water is held and replenished through capillary action – a giant sponge. Depth of bore hole varies but is typically in the 70m-80m range.

Water found, volume and usage agreed, there is one more major consideration before work can commence: Permission from the National Rivers Authority (NRA).

Below-surface ownership

Water below the surface, it seems, is not owned by the farmer who works the land above it. And while many pay vast sums to have land drained of water, the chances of retaining ownership of water which becomes safely stored several metres below are low indeed.

The NRA, with which Mr Martin tends to work closely, is responsible for overseeing and controlling the amount of water extracted from what is in essence, the national lake. Other bore holes in the same area may be affected if a new one is sunk, as indeed, may an important feed to a reservoir.

Obtaining a licence is an involved procedure which requires a series of application forms to be filled in and a sequence of public notification. The degree of complexity, and the time taken for the procedure suggests the application is probably best left in the hands of a company used to such matters.

With permission obtained, Mr Martin organises the drilling rig – drawing on a team of subcontractors working throughout the UK. The diameter of the hole depends largely on the volume of water to be extracted. Typical for a farm requiring say, 2.2m gallons a year would be a hole with a diameter of 25cm (10in).

Drilling takes about a week, the hole being lined first by a temporary steel lining to prevent cave-in during the drilling operation and then, once completed, by a stronger permanent steel casing.

Depth of hole is an interesting detail. Once the water retaining chalk aquifer has been reached drilling continues for several meters to provide an adequate reservoir.

With the hole complete, the gap between the lining and the outside edge of the hole is sealed to prevent soil and stone contamination of the water collection point – a situation which could pose expensive problems for the pump.

Test hole status

At this stage the hole, in the eyes of the NRA at least, is still deemed to be a test hole. A trial pumping reveals if the water supply is sustainable in terms of volume required and if there are any adverse effects on other existing abstraction systems in the locality.

Once all is deemed to be well, a delicate operation follows. The pump – an electrically driven submersible – is attached to a section of delivery pipe and lowered down the hole. As each section disappears another needs to be screwed on, while holding the other end clear. A mistake at this point would see the pump plummet out of sight and the task of trying to retrieve it by attaching something to it 80m below.

It is also interesting to note that, once in position, the pump is actually hanging from the surface by its delivery pipe; below and above it are several meters of water.

One of the main contaminants of extracted water is its iron content which discolours and, if not removed, furs up pipes and causes expensive problems. Treatment is to pass the water slowly through a precipitation tank into which measured chlorine is injected.

The chlorine serves two purposes: It sterilises the water and also causes the fine, unfilterable iron particles to bunch up and settle out at the bottom of the tank. On leaving the tank, water passes through a set of filters and a thick layer of sand.

In operation, the pump is activated by float sensors in a main holding tank – a header tank in a dairy, for example. Domestic and farm demands can then be drawn from this supply.

As with all things, maintenance of the system is essential if all is to work well. Mr Martin recommends the pump is removed from the bore hole every two years for checking, and the precipitation tank cleaned out each year. Filters can be flushed through by reversing the flow of water and the sand replaced. A service/maintenance contract with Marner (UK) can be arranged.

So, what does it cost, and what are the savings? Mr Martin cites the case of the Sussex dairy farmer whose annual bill for water purchased from Southern Water was £10,300 but, with a bore hole, this amount reduced to £686. The investment made amounted to about £35,000 for the whole job.

Water extraction is clearly not for all of us – there is simply not enough water to go round, although one could argue perhaps, that if a farmer is using home sourced water, it reduces the demand on water authorities.


Water extraction costs for Sussex dairy farmer using 10,000 cu m water a year

Cost from SouthernWater£10,300

Cost from borehole (6p/cu m)£600

NRA abstractioncharge£61.68 + £25

annual charge

Total cost£686.60

Saving£9613.32

Gently does it…dropping the submersible water pump at this stage means it plummeting to about 80m (260ft). Retrieving the unit is no easy task.

Marners Chris Martin:An annual water bill of £10,000 can be reduced to about £700.