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The Spanish drought management plans are powerful tools coordinated by River Basin Authorities that prioritise uses and protect water ecosystems under stressed situations through agreed bases among stakeholders. They establish drought phases, describe appropriate measures to be applied at each phase taking into consideration homogenized national drought indicators, mitigate their negative effects and foster a comprehensive follow-up of drought episodes and evolution. As their main achievement, they have avoided applying restrictions in urban areas throughout the recent drought periods.

In the implementation of Spanish Drought Management Plans a wide variety of indicators are used in order to warn for a period of impending drought. These include monitoring reservoir levels, using classical drought indices and assessing uncharacteristic thickness of snow pack during winter. The threat level is then evaluated and defined by 3 consecutive scenarios, each of which require different actions to be undertaken:

1. Pre-alert scenario: The initial stages of drought have been detected but measures are restricted to low cost, voluntary actions such as information dissemination. This scenario is recognised when there is a 10% probability that full water demand will not be met.
2. Alert scenario: Drought is now occurring and actions include non-structural measures of low to medium cost (i.e. restrictions on recreational water use). This scenario is realised when there is a 30% probability that water deficits will occur.
3. Emergency scenario: Impacts of the drought are now visible and water supply is in danger. Infrastructure changes would be applied and urban supply may have to be sourced through different means. The probability of not fulfilling water demand must exceed 50% for this scenario to take place.

Source: Garrote et al. 2006