* Water can be abstracted by a well a short distance upstream of the dam, or by a drain system which collects water from the upstream base of the dam and leads it to the downstream side to a well or gravity-pipe system.
* Where possible, a flushing valve is installed to facilitate cleaning of the subsurface reservoir.
====Maintenance====
* The well or gravity pipe should be regularly cleaned.
* After each large flood, any damage to the dam should be repaired and the dam protected with large stones if necessary.
* For big repairs, such as when a dam has been undermined by infiltration, or damaged by a flood, many people and heavy machinery may be needed, and specialist technicians should be consulted.
Maintenance can normally be carried out by the users of the system or by a caretaker or watchman. Larger repairs may require skilled labour, which can usually be provided by local craftsmen. In some cases, unskilled labour may be required on a large scale (e.g. for repairing a leaking subsurface dam). The labour may be provided by the users (with or without pay), or by other people who are hired for the purpose.
Users may need to establish a local committee to manage issues, such as controlling or supervising water use, preventing water contamination, carrying out O&M activities, financing O&M, and monitoring how much stored water is still available (a piezometer or auger hole may be installed to allow a caretaker or watchman to estimate how much water is left and decide if rationing has to be introduced). Proper management may also help to prevent social conflict. For O&M tasks at the dam site, a person who lives or farms near this site could be appointed. This person could also be responsible for water alloca- tion and be involved in monitoring activities, if users obtain the water near to, or at, the site. His or her authority should be clear and accepted by all users.
==Costs==
