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With empty rainwater tanks and the offer of a good deal I'm tempting to put in a spear pump.

Bore water comes from underground aquifers and requires a bore water pump, also known as a spear point pump to retrieve the water and it pump to the surface. 

We sit on sand within which there are underground aquifers and many folks around town rely on spear pumps to water their gardens.

How deep is the aquifer? It varies. A neighbor struck water 5 metres down.

Assuming I proceed I'm concerned about the constant recycling of salts on annual plants...Annuals and veges are not the local garden norm. But then since my sand is so porous -- it's a sieve anyway -- management presumes some protocols.

Nonetheless, nurseries exist here because they get free water if they have a bore.

..and monitoring any major changes in pH. Also: keep using tank water to 'dilute' any salt impacts.

But I've always been ambivalent about the option.

Water here pumps up iron salts so it is brownish when it mixes with the air and will leave terracotta colored stains on paths and buildings.

To deal with some of the problems there are workarounds:

  • Use infrequent heavy irrigations.
  • Irrigate at night or early morning to avoid evaporation loss and concentration of salts on leaves.
  • Trickle irrigation is better than overhead spray irrigation.
  • Try not to irrigate in windy weather to get an even distribution.
  • Do not irrigate as a fine mist.
  • Do not water under hot windy conditions.
  • It is important to schedule irrigations based on crop needs using evaporation figures from weather stations, tensiometers or other irrigation scheduling equipment.

These levels are measured as TDS (Total Dissolved Solids). Some examples of salt levels per litre for your information:

  • Rainwater: Under 10 TDS
  • Murray River, in places: 600 TDS
  • Sea Water: 35,000 TDS

Tolerance TDS/mg per Litre:

Ironically I've been fertilizing my garden with (a lot of)  DIY urine and have had no -- touch wood -- salt consequences thus far or so I'm aware of..

If the aquifers were at a shallower depth I'd worry. We are, nonetheless, another sand island like Moreton, Fraser,  the Stradbrokes and Bribie --although we're still attached to the mainland.

Most of Bribie Island sits on two aquifers — a deep one below a layer of rock and a shallow one above it. Rainwater soaks into the shallow aquifer and seeps slowly through until it discharges into the sea at the coastline. Some of the rainwater reaches the deep aquifer and then it moves slowly towards the coast. This effectively stops the seawater surrounding the island from soaking into the aquifers.  

Most domestic bores on Bribie Island tap the shallow aquifer and therefore have the potential to interfere with the natural ecosystems.LINK

One day we'll be another sand  island --  sometimes, albeit briefly,  we are an island.

And finally, from out west we learn:

The application of bore water is a very critical point of the gardening. Probably the best advice is to use as little as possible. Where practical use those plants with a low water requirement or which are adaptable to salty or alkaline conditions. Where other species are required reduce the amount of water needed as much as possible by the use of mulches to reduce the amount of evaporation loss, which in this climate can be enormous. Where there is a need for large amounts of water, it is best supplied at less frequent intervals as it helps to wash the salts down away from the feeder roots. Sprinkling for only a few minutes every day only helps to concentrate the salts in the root zone. A good flood once a week is better than a little each day. Where a drip system is already in use, it is usually better to increase the rate of flow, let the plants have a good water, then turn it off and repeat it in a weeks time... LINK

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You will need to consider the capacity of your pump at the boar site as to how many sprinklers it is capable of running.  We have a large pump which pumps water approx., 200 mtrs to the wobblers of which it successfully pumps enough water for up to 7 wobblers.  I will go downstairs shortly and check the capacity of our pump and give you the details if you'd like.

Our wobblers are home made: purchase the base/stand, black pipe and a wobbler.  By creating your own wobbler you can make the height however tall you choose.

Actually I was thinking the opposite: maybe any pump was too strong.

These sprinklers supposedly can run on gravity feed.I'll know after I get one and start experimenting.

Nonetheless I'm not running out 200 metres of hose fortunately. This is backyard irrigation.

Since I FINALLY DECIDED to install a bore my chosen driller turned up yesterday in the rain to search for water. Yes, that's right: in the rain.
So we started walking hither and yon out back while he divined.
Divining the 'streams' is an amazing exercise.
Here they run north/south parallel to the coast because the aquifers are the shadows of previous sand hills -- like gutters or gullies as sand was thrown up onto the shore. It's the same process that made Fraser, Moreton, Stradbroke and Bribie islands.
On my property -- according to devination -- I have two streams running semi diagonally outback.
Does  devining work? -- well my two neighbours just installed spear pumps along the same east west line so I know the water is down there.Another neighbour has a pump 15 years old.
The closest of these is 30 metres away from the site we selected. Here the water is below us almost everywhere as witnessed by the number of spear pumps in use.

Too much underground water harvesting should lead to saline intrusion as the fresh water sits  above the saline.  One driller I spoke doesn't drill when there's a high tide for instance --as the first test a driller makes is for salt. .

But I've been told the some of the water here may come from the Bunya Mtns, just as some of it in Bribie's aquifers emanate from  around Toowoomba. And some fresh water aquifers empty offshore under the sea in Moreton Bay...

But here , for instance, there may be up to three aquifers layered on top of one another with the advantage that salt water is heavier than fresh.
Truly amazing hydrology is it not?

As for dowsing...let's see if we hit a jackpot.

Water divining is a wonderful art! I use a pendulum now and then ... Needed to find where the town water went to after it left the meter and no one could tell me. So the plumber decided to give divining a go. He bent two welding rods and proceeded to walk around where he figured the water pipe would be. At a point, both rods crossed strongly. Dug down and bingo! the water pipe. His eyes bulged as did ours. At the first attempt a non-believer found water using a bit of bent wire.

Well...well...well...

We've started drilling for the spear pump.Into the sand we go, down the tube. Like knife into butter -- and the sand is yellow too.

In the meantime I've been experimenting with my set of Clever Drop Sprinklers. I've got 4 of these. Delightful hardware that they are.

I take one to the school garden to do the irrigating there too while I pot about.

Sprinklers and I have never got on as I'm sure to find something wrong with their performance, but these little beauties are the whizz. The thing I love the most is the raindrop sized dribs. It's just like the rain so walking into the watering arc is like singin' in the rain. A very different experience to other sprinklers of my acquaintance.

Wets so well without drift.

I run all 4 sprinklers off the same hose and tap feed in and the very poor local town pressure works fine. With them all 'on' the garden looks like a miraculous cascade. A setup for $100 (they're around $25 each) is an easy investment: one purchase at a time (Bunnings). I do have a supply of hose connectors and with an archive of old hose pieces to hand all I needed was to invest in another hose line for $6.

Turn it on and I cover the whole planted out garden. And my patch is large.

Each sprinkler has a range of different discs to lessen or increase its arc coverage. 1.5 m to 8 metre diameter: 5 options.

But the killer stat is the flow rate variable per disc:

Approx. litres/min: 2.5 -- 3.0 -- 3.5-- 4.5-- 6.5(no disc).

So 'no disc' for an hour is 390 litres and one hour with the smallest disc --1.25 mm --at 2.5 L/min -- is 150 litres. I'm approximating these figures even with my water tank pump running.

But,


MEASURING YOUR WATER FLOW RATE

Put the source tap on full pressure and see how much water it produces in a minute - you may need several buckets to measure this.

Multiply the number of litres by 60 and you'll know how much water you can pump out in an hour.

 The Science of Watering


If your tank water supply is 'x' litres you can estimate how many chances you have to water the garden before you drain the tanks.

SUGGESTION: use a time switch. Irrigate in the early morning just before dawn. So that the sunrise  works against any fungal consequences. (Main drawback with overhead irrigation compared to drip is the wet leaves.)

BONUS: You can have breakfast watching a sun shower.

BOTTOM LINE: You can establish a water budget: know how much water you are  approximately pouring on the garden, week to week.


ADDENDUM: SOURCE

Here's a handy calculation --albeit from the horticulturalist rule book. It doesn't consider variables like shade or dew and is very schematic, but the scale of the water demanded is, well, shocking. It also doesn't factor in mulch.

But looking at the scenario, I gotta say that my terracotta pot habits scrub up very well indeed.

The next question is how long does it need to run for?

• Simply divide the soil reservoir volume by your irrigation application rate. So in my case, on sandy soil, it’s 8 litres divided by 40 litres per hour equals 0.2 of an hour, or 12 minutes. So we know how long, but just how often?

• The term crop factor means the rate at which plants transpire water in relation to the daily evaporation rate. Waterwise plants, which have evolved various means to reduce water loss, have a very low crop factor of about 0.2. In comparison, vegetables are high water users and they have a crop factor of about 0.8.

• Multiplying this by the daily evaporation rate determines how quickly your plants use up their reservoir. For example a 0.8 crop factor times 10 millimetres (which is Perth’s peak summer daily evaporation rate) equals 8 litres per square metre. This means that in summer established vegies will be using up their reservoir every day.

• The evaporation rate drops in cooler weather, so in autumn and spring, the vegies only need around 4 litres per day or irrigating every 2 to 3 days. In winter this means about 2 litres or irrigating every 7 days. Of course, if rainfall provides the required water, then irrigation won’t be necessary.

So what’s the result?

• If local restrictions only enable you to water twice per week, such as in Melbourne, then you’ll be limited to growing vegetables during the cooler months of the year.

• When the evaporation rate is lower your plants can make it between drinks.

• If you’re in Perth, where you’re also allowed to hand water in between your nominated watering days, then you can pretty much grow all year provided you’re prepared to put in the work.

• But it’s not all doom and gloom. Some vegetables, such as globe artichokes, eggplants, amaranth and warrigal greens have a lower crop factor so they can go slightly longer between drinks.

• If you’re prepared to invest, you can use rainwater or treated grey water and have full control all year.

when we were in Melbourne we set up a grey water recycling set up for the gardens so had water for gardens between watering days - a small 1000 kt tank collected the water and it pumped out on alternate days - if not storage becomes an issue... when we lived in Perth we tried to do the same but not allowed to as the water acqufers were so close to the surface they would become contaminated... so we hooked into the neighbours spear - in suburbia Perth you could run 4 households from one spear . Here in SE Queensland we could drop a spear into an acqufer that starts near the Glasshouse mountains -(apparently a few years ago someone droped blue vegetable dye and watched  where they ended up ) flows under the d"Agular range and exits about 59 metres from our Souhern fenceline !  we have wobble sprinklers set up as a perimeter to the house - to 1, water the garden beds 2. more importantly as a bushfire precaution. yes i was here in the 70s when we were ringed by fire and we kids aged about 10 drove tractors past the police station loaded with milk cans full of water and hession bags food and drinks for the local farmers to help fight the fires  there were fires from Woodford to Samford in them tha hills ! The men were out fighting fires no school for three weeks for the country kids ,the kids were too busy and the women milked cows made sandwiches and did all the other jobs - my mother was a townie so she made sandwiches 80 year old grandmother did our milking !!! so yes I have a thing about bushfires !!!! 

With this sprinkler's design -- it can sit atop a corrugated roof  which suits bushfire protection and house or shed cooling. So rather than stand there with a hose, the sprinkler does the work for you as the ash and flames approach.

Could there be a problem with plastic hoses and a plastic sprinkler catching fire from flying embers?

Here we get a bushfire around once per year usually due to pyromania and burnt stolen cars in the pine forest. To protect your property as it approaches your one other option is stand there with a hand held hose and water your house and garden. In all that smoke blowing your way it isn't a pleasant task.

In the context of escape in rural areas -- maybe not a good idea.

This information is fabulous thanks.  Have you got a photo of your Clever Drop Sprinklers in action or just of the sprinklers maybe?

Here's the company promo:I've elevated mine.I'll share a vid of mine later.

Clever Drop Sprinkler from Wobble-Tee on Vimeo.

Very good thankyou

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