While researching various ways to drill for water I discovered this interesting video demonstrating how one can build a hand drill form plumbing parts and drill for water to substantial depth. This method allows manual drilling for water to depths up to 100m for 3 to 4 days, while the 30m mark can be reached on the first day. While this drill cannot penetrate hard rock and the encounter of larger stones will certainly obstruct the drilling, it is a very cheap method to drill for water and it will work for almost any type of soil. The demonstrated method is developed by the Escuela Móvil de Agua y Saneamiento (Mobile School for Water and Sanitation, EMAS) in Bolivia and is a hybrid between jetting, percussion and rotary drilling. More information can be found on the here.
This is the standard EMAS drilling method:
And this is the suction method:
The following three videos demonstrate how to build the whole drilling set: