Drought poses a threat across Spain, with potential shocks spanning agriculture, energy from hydropower, and broader economic sectors. To help regions plan and mitigate impacts, the government is rolling out a new water forecasting model soon to be shared with the country’s major hydrographic basins, while expanding a network of 80 river checkpoints nationwide with plans to grow further.
The Ministry of Ecological Transition has introduced a system to detect drought alert states by combining recent precipitation and temperature data with near-term projections from the State Meteorological Service (Aemet) and the European Centre for Medium-Range Weather Forecasts (ECMWF). Monthly results from the computational model will be published to keep the public and decision-makers informed, enabling timely responses to evolving conditions.
The aim is to calculate anticipated water contributions in advance for each inter-communal hydrographic watershed, the areas affected by multiple autonomous communities. This supports annual water management decisions within water systems and helps end users plan the hydrological campaign for agricultural or urban needs, aligning supply with demand.
Forecasts will cover the entire hydrological year (October through September) and also project the next three and six months. Contributions are calculated under a natural regime scenario, treating rivers as if no reservoirs, transfers, or other infrastructure exist, to generate a theoretical basis for drought-related decision making.
a challenging summer
The ministry’s first report, based on available data, indicates that water contributions across Spain’s major hydrographic basins are likely to remain below historical norms, with a forecast decline of about 54 percent relative to the long-term average for the upcoming three months, encompassing most of the summer period.
In the worst case, the Tagus basin could see a 72 percent drop, while the Guadiana and Guadalquivir basins may each fall by about 68 percent. The Cantabrian basin is expected to perform relatively better, with only a 38 percent decrease. The Miño-Sil and Segura basins could see decreases around 45 percent, the Ebro around 50 percent, and the Duero and Júcar both around 52 percent.
22 percent drop projected for the year
Looking ahead six months, water contributions are projected to fall by roughly 42 percent compared with the historical average for the entire period, translating to an overall annual decline near 22 percent relative to the long-term mean from October 2022 to September 2023. The outlook varies significantly between basins, with geography shaping the forecast in meaningful ways.
The Guadalquivir basin faces the bleakest forecast, with a predicted 62 percent reduction in water contributions relative to the historical average during the current hydrological year. In contrast, the Miño-Sil basin could see an 11 percent increase in water availability, while the Tagus basin is projected to nearly match the historical record, around a one percent gain.
Other basins are anticipated to experience declines ranging from about 20 percent to 40 percent this year. The Guadiana basin is expected to fall about 18 percent, followed by the Cantabrian Basin at 20 percent, the Duero at 22 percent, the Júcar at 36 percent, and the Ebro around 38 percent. Projections also indicate smaller declines for the Segura, near 39 percent, underscoring the regional nuances that drive water management planning across the country.
Authorities emphasize that these projections reflect a model-based view of natural flow conditions and are intended to inform planning across sectors, including agriculture, urban water supply, and energy. The ongoing data integration from meteorological services and hydrological networks aims to improve accuracy and timeliness, supporting proactive measures in the face of drought, with ongoing revisions as new observations become available. (Source: Ministry of Ecological Transition and State Meteorological Service)