Bottom drains are one of the safety systems of dams and must be prepared at all times to carry out controlled impoundments in case of safety problems in the system:

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• Damage to the dam wall caused by seismic movements or other causes.

• Forecast of floods, with reservoirs at their maximum levels and particularly with free sheet spillway dams.

• Establish previously programmed reservoirs, to leave enough space to laminate the avenue without creating critical situations downstream when it occurs.

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Both in Spain and in the rest of Europe, dam safety committees have been updating the operational requirements for these structures, whose environmental and economic costs are so high that they do not allow their demolition and subsequent reconstruction. These requirements, among others, consist of the incorporation of bottom drainage galleries and derivation pipes of the minimum ecological flows.