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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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In reviewing the literature on watering  via sprinklers I was interested in scheduling, time of day and the length of any irrigation session.

  • morning is best so that evaporation draws moisture off plant leaves as the day heats up. Rationale:so that there is less opportunity for fungal diseases to take hold.
  • while you can do the maths for water flow and time to estimate the volume of the water sprinkled -- a better approach, I think, is to place a plastic measuring jug within the arc of the watering zone and read that after each  session. Balance that with what precipitation is recorded in your separate range gauge.
  • while the traditional rule of thumb for growing vegetables supposedly is one inch to one and a half inches per week, our climate isn't so reliable or predictable.
  • while I was thinking of sprinkling the pumped up bore water once per week for 3 hours my current preference, in the absence of rain, is to turn on the sprinklers for two separated early morning sessions per week of 90 minutes (or one hour or 45 minutes...)  duration each --depending on my volume records and soil moisture 'feel' and the amount of rain over the period.
  • on the off days I can top up my terracotta clay pots irrigators once or twice per week, depending on the soil moisture level.
  • with the Clever Drop Sprinklers I get to adjust the wetting zone by changing discs -- so I've reduced the arc on a couple of sprinklers so that I'm not wasting water over or through the fence line. I now have the garden pretty much covered without wasting flow. I was delighted at how easy it was with 4 stationary sprinklers.
  • the other ruling factor is wind speed. While these sprinklers are supposedly mist resistant (more so at ground level), a strong breeze will carry the droplets further by breaking them up in flight. --at least with the first sprinkler away from the pump. Since I've elevated them, it is good practice to water only when the wind speed is low. That's another reason to water early in the day.
  • despite the elevation -- hip high -- some plants will need to be kept shortened so that the sprinkler arc is not obstructed. The conundrum being that the higher the sprinkler, the more prone the water arc is to misting by wind force. Nonetheless, this hardware generates decent sized droplets -- not like your traditional sprinkler at all.
  • since I have very narrow paths I've deployed them as sponge irrigation trenches or traffic swales so what water goes wherever is all put to use underground.
  • of related interest, I find that if I take one of these sprinklers with me to the school garden for a 2 hour gardening session I can hose the whole garden by moving the sprinkler from one bed to the next while I do other stuff. We also found the sprinkler useful in the heat as the thrill of the wetting them in transit cools the kids.

If the water is only 5 meters deep in the sand could the hole be dug  without getting a drilling contractor  and with the bore water can that be used to flush the toilet and if you have tank water use that to wash the cloths because its the cleanest.

5 meters is pretty deep when digging for water without pressurised equipment.  How would you dig it?  By hand???  Auger would only go just over a meter unless you have a longer one. 

You see a specific width pipe needs to go down into the ground to hold the dirt back from the water.  This pipe has holes in the end that goes into the ground so the water fills up in the pipe and the pump can collects the water and pumps it to the surface.

If its sand  could use water jets  to dislodge the sand from the bottom of a  pipe  like they do with bridge foundations caissons .

Some people do dig by hand. As it is the hole is dug with pipes and water into the sand.

First you dig a round hole and insert a PVC pipe. then you keep dropping a weight  'grab' tube on a rope and start pulling up the enclosed wetted sand. The pipe sinks into the sand rather quickly as you keep pushing it down. We're down 3 metres in less than a hour of effort.

Yellow sand all the way. Some small stones...but tghe best result is to hope for shells as that marks the old shoreline in the gully between pasts and dunes.

My driller returns today. We have some very long pipes to insert as we go. I assume we keep replacing the original pipe as we go deeper.

I also have friends who dug the hole completely with spades and such but being sand, you need a broad hole so it won't collapse on you. On the falt here, folk just dig a shallow dam which serves as a pond filled from  seepage. These ponds are natural phenomenon on Bribie Island. Beautiful they are. 

Not filled by run off but by seepage.

One property down the road here has  avery large pond covered in Lotus Lillies that never seems to drain. And if you ever visit Bribie, Buckley's Hole is an amazing fresh water pond right on the salt water passage.

Truly amazing hydrology.

Dave, have you looked at creating a small chinampas system.  Here is a LINK from the permaculture research institute. 

The problem, Christa, is that the sand doesn't support water at the surface. On the river flats it is easy to create a pond fed by the aquifers.Here the water table is metres down --3.5 to  4 at least.

on the main sand islands -- like Fraser + -- 'perched lakes' are held up by organic matter, such as leaves, bark and dead plants, which gradually build up and harden in depressions created by the wind.

In wetland areas there is some clay but here it is deep sand.

Just out of town there is a property that began life as a fish farm venture with many ponds settled inside the water table -- but on the shoreline/sand pit strip the underground is very different.

I've thought of creating ground level ponds but I'd need to seal the depression with plastics and secure a regular water supply. Another draw back is the fact that such structures would be cane toad and mosquito and sand fly magnets.

And at night...!

Exposed water storages are also prone to much evaporation.

My land is the yellow x in this map image from 1955.  The coastline of Deception/Moreton Bay is to the right (due east) and the long diagonal dark strip is swamp land (now filled in and housing covered). All land has a context.


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