Pond Dilemma

[sbf]

Hope some can help with some options. We have a sloping terraced property, which is currently used for rice growing only but we are looking at options for after the rice harvest to grow other crops. We have a large empty pond at the high point of our property. It is approx. 30m x 20m x 2.5m deep. It was excavated by the previous owner and has apparently never held more than a few cm of water and only after very heavy rain. Our soils are volcanic in origin and pretty free draining around that top part of the property anyway. Normally the empty pond bottom is covered in lush grass which the neighbours graze their cattle on from time to time. My family wanted to fill the pond and then use the land, but I want to at least investigate another option.

As the pond sits at the high point of the property, if we can somehow get it to hold water, then we could use it as a reservoir, and gravity feed irrigate right down the property. This would b especially useful over the dry season, and would open up the cropping possibilities after rice harvest. In the valley bottom, 120 m from the top pond we have several large ponds total capacity more than twice the top pond. These always have water even at the end of the dry season and my idea is to pump from these ponds during the peak of the rainy season to fill the empty top pond.

So any suggestions as to how to hold water in the top pond.

My three so far

Clay line the top pond a difficult job according to the contractor

A liner of some kind, but what type, where to obtain and at what cost

Concrete line the pond - the contractors suggested solution.

Any others, and any comments on the merits or otherwise of any of the above.

[Jotham79]

It would have been nice to know a little more about the size, shape, location of your property, what crops you wish to plant, but here goes:

I would not try to seal your upper "bowl". If, anyone tells you how easy or cheap it is, go see the pond the one they actually did and see how similar your pond is with theirs.

If you can pump water from the other ponds to fill it then you can pump to a small concrete tank to gravity feed irrigate.

When you pump water from the lower ponds to another pond you increase the total surface area of water and increase the evaporation proportionally.

Irrigating from ponds, takes a lot of water (it's what I do). If you want to put 2 cm of water on your land with sprinklers you will need to pump 4 cm or more. On a really hot dry day with a breeze it is almost not worth the while. This would be a little less for gravity, and even less with drip but there will still be some loss. So every time you water 10 rai of land you want to water you lose about 40 cm of water from a 1 rai pond. (I have rounded out ot account for other loses, which there will be) count for normal loss from irrigation and you can see that you can go through water in a hurry. If you run out of water, your crop is most likely be entirely lost. The profit margin for irrigating crops makes many crops very risky.

I irrigate about 20 rai (I have more) through the dry season and have 2 ponds each almost 1 rai and 4 meters deep and another about half as big. Not all land can be covered by all ponds. I can usually (but it is not guaranteed) fill them 1 time from an irrigation ditch that runs along my property.

For what little you can possibly gain, the cost will be high. Fill or don't, but I would look at a "forgiving" crop for dry weather and drip irrigation. Or maybe even better, consider raising tilapia in the ponds.

good luck

[sbf]

Dear Jothan79,

Many thanks for your detailed reply, plenty to think about in it. The land is in southern Sisaket province about 18km from Khantharlak. It is just on 20 rai and very roughly rectangular in shape approx. 300m by 110m. The empty pond is in one corner and the permanently full ponds are from 120 to 200m away in the valley bottom down the long side of the rectangle.

Crops we are looking at are Tomato, Cucumber, Watermelon and Sesame.

[canuckamuck]

What is the dimensions of your pond?

[sbf]

Hi Canuckamuck,

The empty pond is 30 x 20 x 2.5m. The three full ones are 30x20x2.5m, 15x10x2.5 and 15x10x3m

[Jotham79]

Depending on the gradient, it may be very difficult to get water up the hill. Try this as an experiment to see if it can bee done. Then measure the depth (surface to bottom) of the lower ponds at the end of the rainy season to give an idea of how much water is really available. Understand that the sides are sloped and if you assume 2 meters of usable depth and a 2:1 slope (very steep) then you have about 2,000 cubic meters of usable water (very ball park). I don't see you having enough to water the whole 20 rai for a dry season. I have around 10,000 cubic meters that I can sometimes replenish and I would not try it. Cucumber and tomatoes take a lot of water ( I grow both, but not in the main dry season) or if do then in small patches of 1-2 rai and the more you spend pumping water the less profit you make. If you can pump with electricity it will help. You can make money, but it is more difficult and you have to be able to time the market to some extent. I have not a clue about sesame seeds.

Try this: Take about the best 4-6 rai nearest the bottom ponds and try to plant and water them next year. Try different crops and see how it goes. I don't know who will do all the work, but this is a lot of land for a couple of people and if you start hiring a lot of labor it is near impossible to make a decent profit. I have tried dozens of different crops at different times of the years. I hope you have better luck in the dry season. Too bad you are so far away, I'd have you come for a visit.

If you want to do the whole 20 rai, I would try mungbeans (no personal experience yet, but have seen it done and will plant this year). The second thing I would look at is cassava with drip irrigation (no experience with this, but will this year).

Again, good luck