Digging in this type of soil by hand is HARD, backbreaking work, and all done without the benefit of heavy machinery. Looks like quality workmanship.
Modernity really takes the fun out of hard work. Much respect to hard working people of the world.
We place a precast reinforced concrete (RC) cylinder perpendicular to the site. We start digging in the inner ground and the heavy roller will go down on its own. Once the roller is level with the ground, place another roller on top of it and continue in this way until a deeper level of clean water is available. Water will leak into the well between the rollers. Several top roller joints can be combined with sealant to prevent contaminated water from higher levels from seeping in. There is no danger of wall collapse.