Can one pump water without providing an external source of energy? I have a farm situated right beside a canal through which we use to get water for our crops. I am not financially sound to buy an electric motor. The water is 15ft below the ground level. So can anybody suggest me a feasible way to get the water out of it by using air pressure or any simple instrument that helps me out? Here I attached an image for reference
 A: First of all, anything which raises water is by definition a machine, and further unless you wish to defy the laws of physics, will require external energy input.  Now, if you want a simple machine,  I'd recommend the Archimedes Screw,  http://en.wikipedia.org/wiki/Archimedes'_screw .  It's a simple thing to build and operate.
A: The power of the water stream can be used to pump it up continuously, if it is reliably flowing as on the picture.
Have a look at results in Google from "watermill irrigation" keywords, you get e.g. http://www.panoramio.com/photo/59986317
Maybe then you have to worry about how much work it is compared to your water needs, and would it be worth doing if periodic flooding presents a risk to damage your work (the structure on the left looks like a dyke, doesn't it?). 
Alternatively, using muscle power, a lighter system would be a shaduf, in order to get a one bucket at a time: http://en.wikipedia.org/wiki/Shaduf

Finally, if the structure really is a dyke and your farmland is lower down on the other side, it may be worth to dig a pond on that side, connected to the water stream with a flexible tube above the dyke. Once the tube is filled up with water, the pond will re-fill whenever you pump from it, which will be much easier than from the canal.
A: Another possibility would be a hydraulic ram, but I'm not sure if you can build it on your own. Another problem is the water flow of the river, but you can have a look at it:
http://en.wikipedia.org/wiki/Hydraulic_ram

