The EMAS pump can be made from different sizes of PVC pipes and a marble. Compared to a rope pump, the EMAS pump produces water under pressure. So you can pump up water to a higher lever then where the pump is. EMAS pumps are also cheaper and easier to make. Yields are however in general less the a rope pump.
There is a ton of useful information and instruction videos at www.emas-international.de also about other low cost technologies. We advise to have a look.
Get the manual at: http://jacana.help/resources/water#makeemaspump