Changes

====Build the pond====

* Small dams tend to fail much more frequently than larger dams, and this seems due to poor siting and design, lack of design, poor construction techniques and lack of maintenance. One example in Sudan demonstrates this where breached dam embankments were attributed to a gross underestimation of the runoff volume, as well as poor overall design. Proper design, construction and maintenance are therefore important. The following are guidelines used for hillside dams maximum 3m high, where water is retained by an embankment. For heights over 3m, other guidelines are available.

# Material used for the dam wall should be impermeable. It should have a high clay content (55% minimum), as long as cracks do not form which would induce piping and leakage. The following materials are to be avoided: organic material including topsoil and that with roots/stones, decomposing material, material with high mica content, cracking clays, calcitic clays, fine silts, schists and shales, and sodic soils (high sodium concentration). Piping is often a major reason for structural failure of dams and can be recognized by increased seepage rates, discoloured seepage water, sinkholes on or near the embankments and whirlpools in the water.