Irrigation

[Pond Life]

There's been quite alot of discusion of irrigation on the "Growing Makua" thread.

It seems that the most economical use of water is by drip irrigation, a step further & use of gravity feed eliminates the cost of a pump.

But what if youre not lucky enough to have a naturaly elevated water source.

Take a look at this link,

http://www.lurkertech.com/chris/eco/

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http://www.lurkertech.com/chris/eco/

This site belongs to a guy in Pai & contains many other links for water powered water pumps.

Here's some samples

http://www.thaivisa.com/forum/style_images.../attach_add.png

http://www.thaivisa.com/forum/style_images.../attach_add.png

http://www.thaivisa.com/forum/style_images.../attach_add.png

The flow of water in the stream or canal turns the wheel,

At each revolution the water intake is submerged & fills the lowest part of the pipe,

As the wheel continues to turn the water travels along the spiral towards the center,

Each succesive turn adds another slug of water, with air trapped between,

As the water & air travels towards the centre of the wheel the air is compressed & the pressure of the air & water increases until it reaches the hollow axle from where it is transfered via a rotating coupling to an external pipe to your elevated water tank.

This looks to me as if its idealy suited to the small concrete canals you find in most rural areas of Thailand.

What do you think ?

Ever seen one in action ?

[lingling]

This looks to me as if its idealy suited to the small concrete canals you find in most rural areas of Thailand.

What do you think ?

Ever seen one in action ?

You'll have a hard time convincing the local farmers that it is not going to affect them if you install one of those in the irrigation canal leading to their rice paddy.

[chownah]

Assuming that this thing rotates slowly then you can not lift water higher than the inlet when it is at its highest point at the top of the wheel with this device. To pump water you must create pressure....the only way this device can create pressure is by lifting the water and the water's weight then makes the pressure....the highest it can lift water is to the height that the inlet reaches at the top of the wheel so that is the highest the water can go.

Q: Assume you could pump up 10 feet further.....where is the pressure going to come from to get this extra height?

A: There is nothing on this device to create pressure other than the depth of the water in the device itself so pumping any higher is not possible.

Chownah

Edited January 23, 2007 by chownah

[Pond Life]

Ling Ling, yes I agree, convinceing the Thai's to try something new is an uphill battle, particularly with something as sensitive as their irrigation system. But show them something that can save them deisel (for those that live above the klong) & maybe they'll get interested.

However, there are certain members of this forum who are equaly blinkered, which brings me to you Chownah.

You have very obviously not read the links I supplied.

Go to the lurkertech site for which I provided a link.

Follow the link for "Tailer Spiral", there you will find a report on a practical working model that succesfuly pumped water to 60 ft, yes, nearly 20 m.

After that follow the thread for "Mortimer Coil", where you will find scientific research that explains why it works, page 3 in particular explains the effect of a "series manometer" very clearly.

You as an engineer should have no problem understanding this concept.

In future do the posters the decency of reading the information supplied before passing comment.

As a baby engineer I was taught "think twice, cut once".

[Pond Life]

Back to the drip irrigation, can anyone thats used this system tell me what size filtration I need if I'm useing emiters of 4-8 lt/min. Have you had much problem with blockages ?

[chownah]

Ling Ling, yes I agree, convinceing the Thai's to try something new is an uphill battle, particularly with something as sensitive as their irrigation system. But show them something that can save them deisel (for those that live above the klong) & maybe they'll get interested.

However, there are certain members of this forum who are equaly blinkered, which brings me to you Chownah.

You have very obviously not read the links I supplied.

Go to the lurkertech site for which I provided a link.

Follow the link for "Tailer Spiral", there you will find a report on a practical working model that succesfuly pumped water to 60 ft, yes, nearly 20 m.

After that follow the thread for "Mortimer Coil", where you will find scientific research that explains why it works, page 3 in particular explains the effect of a "series manometer" very clearly.

You as an engineer should have no problem understanding this concept.

In future do the posters the decency of reading the information supplied before passing comment.

As a baby engineer I was taught "think twice, cut once".

OUCH!! What a stinging rebuke!!!! Do I really deserve to be treated so harshly? I didn't look at the links...any of them....I wasn't aware that any of them dealt with the contraption you showed pictures of....

I'm so sorry to have acted so indecently....I'll try to live up to your standards in the future...or maybe not.

I'll go look now and come back and post again.

Chowanh

[RamdomChances]

Try and keep things civil can you guys, thanks RC

[chownah]

Pond Life,

I took a look at the site and this is indeed an interesting concept and in some situations may be an excellent pumping solution. I like the fact that it can be constructed without the need for sophisticated equipment or materials. I do maintain the assertion which I made in my original post, "Assuming that this thing rotates slowly then you can not lift water higher than the inlet when it is at its highest point at the top of the wheel with this device." I believe that a certain minimum speed is required for it to function and that by using smaller diameter tubing you can create a machine that will function at a slower speed....but that there will be a lower limit as to how slow it can turn and still function. I think I understand its pumping principle now but I won't bore you (or any of the other good readers here) with the details.

I think it would be interesting if someone built one from clear tubing (something I did not see indicated as having being done at the web site) and then you could see how the water is moving which I think would help in understanding how it works and how to optimise its function.

Chownah

Edited January 24, 2007 by chownah

[lingling]

Pond Life,

I took a look at the site and this is indeed an interesting concept and in some situations may be an excellent pumping solution. I like the fact that it can be constructed without the need for sophisticated equipment or materials. I do maintain the assertion which I made in my original post, "Assuming that this thing rotates slowly then you can not lift water higher than the inlet when it is at its highest point at the top of the wheel with this device." I believe that a certain minimum speed is required for it to function and that by using smaller diameter tubing you can create a machine that will function at a slower speed....but that there will be a lower limit as to how slow it can turn and still function. I think I understand its pumping principle now but I won't bore you (or any of the other good readers here) with the details.

I think it would be interesting if someone built one from clear tubing (something I did not see indicated as having being done at the web site) and then you could see how the water is moving which I think would help in understanding how it works and how to optimise its function.

Chownah

Maybe a more efficient use of the wheel would be to let it power a piston pump or water screw?

[chownah]

Lingling,

Maybe so...I don't really know. The link Pond Life gave had some stats on efficiencies but I really don't have the time to analyse what they presented. It is quite an involved site and they have done alot of good experimentation and analysis. I think that anyone who has a good volume of water flowing in a stream or canal might be able to use one of these....unfortunately I am not in that category. One advantage of this wheel is that it has no valves and the only moving part is the wheel on the shaft....the site points out that there is one that is still functional after over 200 years. Another advantage is that the entire thing can be made with simple tools....try making a piston pump at home with common hand tools....or a screw pump.....for most people an impossibility...but this wheel is do-able.....and if done with a funky artistic spin I think it could be a total delight to watch in action!!!!

Just to clarify my previous post....the site indicates that their wheels can pump at 2 rpm which I will admit can be described as "slow" but in my comment by "slow" I meant inch by inch slow.

Chownah

[Pond Life]

Yes Chownah, I think you did deserve that, but thank you for reconsidering you view.

Water wheels can be used to drive conventional pumps, but most pumps need to turn at a reasonable speed & would usualy require some sort of gearing & power transmission (belt drive, chain & sprocket or gearbox). This is inherantly ineficient, mainly I think due to friction.

The spiral pump doesnt need gearing or power transmission & is therefore more efficient.

Also it only realy has one moving part (admitedly running on 2 bearings) compared to some types of pump that have many moving parts (therefore more friction & more things to wear out or break).

There's also the cost factor, if you drive a conventional pump from a water wheel you've got to pay for the construction of the wheel + buy a pump, where as with the spiral pump once you've constructed the wheel all you've got to pay for is the apropriate lenght of flexible pipe (cheap).

If supplied with enough water flow (not much I think) it will run 24 hrs a day at no additional cost to the owner & as it is operating at very low RPM it should suffer very little wear & tear.

Anyway the proof of the pudding is in the eating, I'll hopefully be making a small wheel in the next few months, I'll let you know how it goes, hopefully it wont taste like humble pie.

[chownah]

I've gone out and read some more and I am now of the opinion that my original analysis was completely wrong and this device will pump even when turned very very slowly.

Live and learn....or the alternative is live and don't learn.

Chownah

[Pond Life]

Thanks Chownah

[chownah]

If I didn't stick my neck out and post my original analysis I probably would not have learned as much about this device. If you had not challenged my analysis I definitely would not have learned as much about this device.

Chownah

[Pond Life]

Ok, so we've got a 24 hour, never ending, free water supply (I exagerate I know).

Now we need somewhere to store it.

I've never been to impressed with tanks made from stacked up well rings.

Pond might work if the lay of your land is right.

But im coming to the conclusion that a round ferrocement tank built without shuttering is probably the best option for me, probably the cheapest also.

Managed to find a good site with step by step directions on how to build one, link below.

FERROCEMENT.COM

Has anyone had any experience owning or building something like this ?

Think its a good idea or not ?

Edited January 25, 2007 by RamdomChances
sorted the link out RC

[Pond Life]

Bugger that link doesnt seem to work.

Im a better mechanic than I am a computer geek, honest.

Anyway here's the long way to find it.

goto www.ferrocement.com

Choose your prefered language

Click Aquaculture/Tanks

Under the diagram of a round tank theres a clickable link for guide to building tanks.

Good luck.

[pallasaide]

In Tims opinion, all the alternative methods described in this thread are great ideas.

The key to them is of course using drippers, which instead of throwing out large volumes of water to feed the whole field and all its weeds, instead concentrate the water around the plant that needs it, do not require high pressure to operate properly and do not waste it

Low pressure equals low energy requirement.

Drippers are a great way for watering vegatables, and there use will slash your energy bill. There is no need to water vegetables quickly, in fact with as little as 2m elevation (whether in a tank or on higher ground) a slow watering that results permitts using any of the above methods as they do not have to replenish the raised water supply fast.

By the same token, a couple of 100watt solar panels (or even one) can supplement amy of the above alternative systems to move a substantial amount of water (thousands of liters an hour) to a several meters elevation for stroage to supply drippers.

D.V.

[Pond Life]

Solar is great, Im running my house off it, but boy is it expensive.

200 watts of panels will cost in the region of 40,000 B, thats before you buy the pump.

I think I can build a 2m wheel pump for about 5,000 B give or take 5 k (Im guessing ok), dont know how much water it'll pump but it should run 24 Hrs compared to 10 Hrs max for a solar system (unless you add batteries).

But then again a wheel is no good if youre getting water from a bore.

Yes DV/Tim, I meant the semi rigid pipe, 3" dia, comes in rolls about 2 m dia, I thought using that would eliminate alot of joins & it should be more resistant to sunlight. So i guess I'll have to look for a shop that sells rubber tits.

Could you grow Potatoes with the bucket/drip feed system ? presumeing your weather is cool enough.

You have to bank spuds anyway so why not in a bucket ? harvesting would be a doddle, or am I missing something ?

Also with the bucket method, at the end of a growing cycle do you re-use the soil for the next crop or discard it & get fresh soil or mix the old soil with some fresh compost & manure ?

[pallasaide]

Pond Life

Tim tried potatoes once, and it was a complete faliure.

The fact is, unless you are in the highland region around Changmai or Changrai, you just do not have the climatic conditions in Thailands to grow potatoes successfully. There is no way way that one was his conclusion.

[Pond Life]

Right first time, Im in Mae Hongson area NW of Chiang Mai. about 500 meteres alt.

Average morning low for Dec was about 9 deg C with thick dripping mist.

Daily high 25-30 dec C, very low humidity, zero rainfall.

They definatly grow spuds round here but might be higher up the hill.

I was just wondering if there was any particular reason potatoes wouldnt like the bucket & drip system presumeing all other variables were ok.

[chownah]

In places where there is enough water to run a spiral pump a good alternative for economical irrigation is the tube pump. Tube pumps are those long tubes that farmers use to pump water using a two wheeled tractor commonly as the power source. I have a 5 inch diameter tube pump that is 6 metres long which cost about 3000 baht. When I use it, fuel consumption is less than one litre per hour and it pumps a really large volume of water per hour....probably enough to irrigate one rai of vegies but I don't know for sure because I don't have one rai of veggies to irrigate yet. A tube pump is a portable turbine pump and a turbine pump is perhaps the most efficient design for pumps.

Maybe Maizefarmer has some specs on pumping rates and fuel consumption of tube pumps or is willing to share some of his experience with us.

Chownah

Edited January 26, 2007 by chownah

[chownah]

Ok, so we've got a 24 hour, never ending, free water supply (I exagerate I know).

Now we need somewhere to store it.

I've never been to impressed with tanks made from stacked up well rings.

Pond might work if the lay of your land is right.

But im coming to the conclusion that a round ferrocement tank built without shuttering is probably the best option for me, probably the cheapest also.

Managed to find a good site with step by step directions on how to build one, link below.

FERROCEMENT.COM

Has anyone had any experience owning or building something like this ?

Think its a good idea or not ?

Pond Life,

The round tank you are suggesting has a domed top with an access hole and cover. Do you think that the domed top is necessary for irrigation purposes? It seems that some money could be saved by eliminating the top and reinforcing the top edge a bit. Also I did some preliminary calculations for the amount of rebar needed to build an in-ground rectangular tank with the same capacity and it took less rebar and there is no need for the welded wire, chicken wire, or expanded metal...so there might be some cost savings with an inground rectangular tank...but I have not done a complete estimate of quantities. What do you think?

You mentioned that the ferrocement tank was the best option for you. What feature is it that especially meets your needs? Knowing this then perhaps other designs could be suggested since the ferrocement tank does seem to require alot of steel which is a major cost item.

Chownah

[Pond Life]

Yes, a fair point, here's my thinking & Im definatly no expert in this field.

1. an in ground rectangular tank will need less re-bar etc but you will have to buy alot of plywood & timber for the forms, this is supriseingly expensive & most of it will get thrown away afterwards.

2. a poured tank will have to be thicker, hence more cement,sand, stone. & should be made in one pour, where as the round ferro tank can be plastered bit by bit.

3.Im planning to put the tank on the highest point of my land so I can gravity feed, putting it in the ground would lose me 2 m of head.

4. Lid or no lid, Im still undecided on this one.

No lid is cheaper & easier & there are diagrams on the same site for the rim re-enforcement.

A lid would keep the water free of debris, animals & most importantly mosquitoes.

All that said, im considering an in ground tank for rainwater storage, for domestic supply, mainly to hide it as it will be right next to the house.

[chownah]

Pond LIfe,

I looked around for info on water tanks with cold joints and in short order found this site:

http://www.backwoodshome.com/articles2/ainsworth101.html

It is a detailed commentary about one persons experience building a 6,500 gallon concrete water tank....above ground....with cold joints....at the time the article was written the tank had evidently worked well for 23 years in spite of it using a 1:3:5 concrete mix which I would suggest is substandard...I build with 1:2:3 mix. They say they used rebar every 2 feet (60cm) but they don't say what size rebar it was....wall thickness was 8 inches (20cm). They used a sealer (Thoroseal) and when my stacked ring water filter/tank combination was built here in Thailand they used a sealer on the inside and that sounds like a similar thing. This filter/tank is constantly full of water and the outside surface is dry....there was a slow seep at one spot but over time a crystaline mineral deposit has grown there and I think it has stopped seaping entirely but I haven't really checked it closely because even at its worst it was insignificant.

So...to indicate how this method addresses your concerns:

1. Since cold joints don't seem to be a problem the tank can be built in small sections so you could seriously reduce the amount of form materials required....also used form boards can be sold....they should never be discarded. I have a nice selection of form boards around (I've even got a big collection of 15 cm C-channel that I use exclusively as forms...I'm always building something it seems!!) and use them over and over again...just be sure to store them in a dry place and up from the ground. They can also be cleaned up after use and then used as boards for wood construction in places where appearance is unimportant.

2. More cement, sand, and gravel for sure but evidentally the single pour technique is not necessary.

3. They built above ground so you wouldn't lose any head from the water at the bottom of the tank and depending on the height of the top you might lose some head from the top...or maybe not if you built a tank of the same height...although the design I have been fiddling with is only 140 cm tall. By the way..how much head are you needing for your irrigation?....and how much head will your tank design give you when full?

4. They built a wooden cover...I don't think a cover is necessary but a blue nylon screen panel could be stitched together using nylon line for really cheap and would keep insects out and I don't think that animals will be too interested but I maybe I'm wrong on this...seems like verticle walls would be hard to climb...and if they did want to take a drink I'm wondering if this is actually a problem or not. I think that mosquitos require a particular depth but I suppose that the tank might be left at that depth inadvertantly and they could colonize at least temporarily...I guess.

Anyway...just another possibility...I'll keep working on the cost estimate for a similar tank just to see how it comes out.

Chownah

Edited February 1, 2007 by chownah

[Pond Life]

Im going to try again with the link to the ferrocement tank site, I just noticed that theres a capital B in the adress, which might be why it didnt work, i've heard these computer things are rather picky about their grammer, unlike me.

& I also dont know why the link comes up twice but only the second one does anything, Ramdom ?

Ok deep breath here goes,

http://www.ferrocement.com/tankBook/indici.en.html

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http://www.ferrocement.com/tankBook/indici.en.html

[Pond Life]

I've just read the backwoods article.

Sounds like she did everything against all the usual advice, especialy no re-bar in the floor slab, but, 23 years of trouble free service cant be argued with.

Chownah, if youre going to run the calcs on this how about doing it with a bit more conventional mix & re-bar layout. It may have worked for her but I would have difficulty putting that amount of money & effort into something that is basicly a bodge up.

[chownah]

I've just read the backwoods article.

Sounds like she did everything against all the usual advice, especialy no re-bar in the floor slab, but, 23 years of trouble free service cant be argued with.

Chownah, if youre going to run the calcs on this how about doing it with a bit more conventional mix & re-bar layout. It may have worked for her but I would have difficulty putting that amount of money & effort into something that is basicly a bodge up.

So far I've been designing a tank with inside measurements of 9.6 x 4.6 x 1.4 metres...this hold 60 cubic metres the same as the ferrocement tank. This allow for using full length (10 metre) rebars the lenght and half length pieces across the width....with no waste. I've used 9mm bars on 30cm centers both ways everywhere...basically a 30cm square grid of 9mm rebar. The wall verticle bars extend into the floor for anchorage. I've been designing a perimeter beam at the top edge of the tank using 4 strands of 9mm bar in addition to what is located there from the 30 cm grid and 2 metre long pieces of 9mm every 30 cm as corner ties to strengthen the verticle corners.

I haven't checked my figures yet for accuracy but it looks like 87 bars (each 10 metres long) and estimating 90 baht per bar this means 7830 baht for the bulk of the steel....there will be some smaller quantities of restraining steel (ties) but I haven't estimated them yet.

This design is about what you can expect in a swimming pool design from what I've seen.

As a comparison I used the ferrocement tanks estimate for their (12mm) rebar only (not including the wire mesh or expanded metal or chicken wire) and converted it from 6 metre lengths to 10 metre lengths and using their version using the least steel I came up with 51 pieces (10 metres long each) and estimated at 190 baht per piece giving a total for rebar only for the ferrocement tank of 9690 baht.

So, given that if you didn't construct the top of the ferrocement tank (my design has no top) and given that I need to add a bit more for some rebar details that I've not done yet, then the cost estimates for the rebar for the two designs is about the same...remember this is rebar only and not the other steel that the ferrocement tank requires.

I haven't done the concrete calcs yet....this is where my design will cost more than the ferrocement tank for sure.....I'm using 20cm thick concrete everywhere....If you see any mistakes or have suggestions or ideas feel free to post to let me know what you're thinking.

Also, are my prices for 9mm and 12mm rebar correct?

Chownah

[Pond Life]

Good idea to size the tank to the length of re-bar.

You didnt mention if theres steel in the slab ?

What are you baseing your 9mm 30x30 steel layout on ?

20 cm walls sounds like alot, I think 15 cm is more standard, whats the cost play off between 20 with less steel & 15 with more steel ?

The ferrocement tank looks bomb proof but the Backwoods one doesnt.

Sorry, cant help with steel prices, just had some building work done but now Im out of the country.

[chownah]

The slab has the same 30x30 cm grid of 9mm rebars as the walls....its the same everywhere.

This 30x30 cm grid of 9mm rebar is what is often used in swimming pools.

The 20 cm is indeed hefty but I thought I'd go for a design that I felt could be above ground...design the deluxe version first and then trim it down later.....by the way, I'm not certifying this design and no one should build anything based on my designs...they should consult a structural engineer or decide for themselves what is appropriate.

I'm trying to figure out how to estimate the cost of the concrete. My design takes about 18.5 cubic metres while the ferrocement tank takes about 5.5 cubic metres without the cover and hatch. Finding the quantity used is the easy part...I'm having problems with the cost per cubic metre. They use one cement to three sand (volumes). When I build with concrete I use one cement to two sand to three crushed rock (volumes). I am using a very rich mix which will yield a much stronger than average concrete. The Backwoods tank used 1:3:5 which is about as weak as you would want to go to build anything...but it worked. So I'm still considering what is a good way to estimate this. If I say 10 bags of cement to 1 cubic metre of crushed rock to 2/3 cubic metre of sand with cement at 120baht per bag, rock at 500 baht per metre and sand at 330 baht per metre then on cubic metre of concrete costs about 2000 baht and the total cost for concrete for my design would be about 37,000 baht....so I consider this to be an upper estimate for the cost of concrete for my design.

If the mortar for the ferrocement tank costs the same per cubic metre then the cost there would be about 11,000 baht which leaves a deficit which my design needs to make up of 26,000 baht which would possibly come from the extra steel needed for the ferrocement tank.

Does anyone out there know the price for 6,6,10,10 welded wire? That would be welded wire mesh with 15 cm square spacing of 10 gage wire (I think 10 gage is about 3.5mm).

The ferrocement tank might look bombproof to you but it looks like an eggshell to me. There are different kinds of strength. I think my tank would take a bump from a vehicle better than the ferrocement tank would but I could be wrong.

Chownah

Edited February 3, 2007 by chownah

[ozzydom]

Pond Life

Tim tried potatoes once, and it was a complete faliure.

The fact is, unless you are in the highland region around Changmai or Changrai, you just do not have the climatic conditions in Thailands to grow potatoes successfully. There is no way way that one was his conclusion.

Not quite true , there is a very successful broad-acre farm growing huge amounts of potatoes situated between Sawang Daen Din and the Mekong in Issan, managed by a Kiwi .nearly fell over when I saw the size of the travelling sprinkler booms run off multipe 12 inch pumps.