Drought in the Indices, but Not in the Warning System
As Croatia enters a new heat wave and the SPEI index shows a worsening water balance, the question resurfaces: why is there no unified official drought warning?
As Croatia enters a new heat wave and the SPEI index shows a worsening water balance, the question resurfaces: why is there no unified official drought warning?
On August 5, 2026, Croatia enters a new heat wave, with forecast models predicting a further rise in the Standardized Precipitation Evapotranspiration Index (SPEI) and a worsening water balance. Yet, while meteorological data already signal drought conditions, the public is increasingly asking: who is actually responsible for issuing an official drought alert?
According to data from the State Hydrometeorological Institute (DHMZ), conditions for drought development have already been met. The SPEI index, derived from comparing precipitation amounts with potential transpiration and evaporation using measurements from meteorological stations, clearly indicates when the water balance shifts into a drought state. As temperatures rise and precipitation fails to materialize, the index quickly enters negative territory.
Despite this, Meteoalarm, as a warning system for hazardous weather events, does not treat drought in the same way as storms or heat waves. The difference lies in the duration of the event: a heat wave lasts up to two weeks and has clear parameters for forecasting, whereas drought is a process that develops over weeks and months. Consequently, drought conditions are monitored through indices like SPEI, hydrological balance, and soil moisture, rather than through the standard system of orange or red alerts.
When it comes to low water levels in surface and groundwater, Croatian Waters is the institution responsible for hydrological monitoring. This institution continuously tracks water levels, flow rates, and groundwater conditions, regularly reporting on hydrological information and issuing warnings in the event of potential threats to water systems, supply, or safety.
However, for low groundwater levels, there is no standardized, widely recognized warning system like the one used for meteorological threats. It is more of a system of expert oversight and hydrological monitoring than a classic public-communication warning. In other words, Croatian Waters has the capacity and responsibility to be the primary source of hydrological warnings, but in practice, this aspect has not been established as a comprehensive national drought alarm.
Experts warn that a drought warning should not be solely a meteorological issue. It is a cross-sectoral topic that links DHMZ, Croatian Waters, the agricultural sector, fire protection, and civil protection. The meteorological aspect of the warning should stem from a system that monitors precipitation, heat, and evapotranspiration, while the hydrological aspect should be tied to surface and groundwater conditions.
For an effective drought warning, Croatia should have an integrated system, not just a single organization and a single indicator. Drought is not merely a lack of precipitation but also the result of prolonged excess heat, increased evapotranspiration, and reduced water reserves in soil and underground layers.
For comparison, in neighboring Slovenia, drought warnings are common. Official monitoring and assessment of conditions are carried out by the Slovenian Environment Agency (ARSO), which regularly reports on drought conditions in agriculture, surface waters, and groundwater. State bodies, particularly ARSO and the relevant ministries for environment and agriculture, are responsible for systematic management and implementation of drought-related measures. Information from ARSO is used for timely notification of worsening drought conditions and for assessing potential impacts on agriculture and water resources.
According to weather forecasts, the upcoming heat wave will add further pressure to an already weakened water balance. As temperatures rise, so does potential evapotranspiration, leading to faster drying of soil and vegetation. If no significant precipitation occurs, the SPEI will decrease further, and the drought signal will become stronger not only at the meteorological level but also at the hydrological level.
The key fact is that drought does not occur only when rain stops, but when heat takes control of the water balance. This heat wave is therefore more than just a weather event-it is part of a process that is already affecting water conditions, agriculture, and ecosystems.
