Title: The Homemade Water Shortage: How the Withdrawal of Coal and Nuclear Power, Heavy Industry, and Environmental Regulations Changed Atmospheric Humidity

Introduction:

In recent decades, the hydrological balance has shifted noticeably in many temperate zones of Europe, particularly in Germany and Central Europe. While global warming, global air circulation patterns, and changing precipitation distributions are widely considered the main causes of increasing aridity, an often overlooked aspect is becoming increasingly relevant: the homemade decline in technical water vapor sources due to structural changes in energy generation and industrial production. This article sheds light on a little-noticed hypothesis that is gaining relevance in research: The withdrawal of primary power plants such as coal and nuclear power, as well as the widespread shutdown of heavy industry, may have led to a reduction in anthropogenically released water vapor—and thus contributed to the regional intensification of drought.

Thermal power plants—especially coal and nuclear power plants—require enormous amounts of water for cooling, which is then released into the atmosphere in the form of steam via cooling towers. This artificially released water vapor represented a continuous source of atmospheric moisture for decades. In industrial regions, countless cooling towers, evaporator systems, and hot process chains resulted in water vapor, a byproduct of industrial activity, influencing the regional microclimate. Even though these processes placed long-term environmental strains, they simultaneously generated local humidification of the lower troposphere through evaporation effects, which acted as a buffer against drought during periods of low precipitation.

The complete or partial withdrawal of these technical sources of moisture as part of decarbonization, the phase-out of nuclear power, and the relocation of energy-intensive industries abroad leaves a noticeable gap in the atmospheric water cycle. In addition, there are stricter environmental regulations that restrict the return of cooling water to rivers or minimize evaporation through new technologies (e.g., closed cooling systems). The question arises: Have we inadvertently triggered atmospheric dehumidification through well-intentioned ecological measures?

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The aim of this article is to illuminate this previously neglected connection from various perspectives and, based on six thematic focuses, to critically analyze the role of technical water vapor inputs in the regional water balance. This does not question the fact that climate change is a global driver of change – At the same time, local technical interventions in the atmosphere must be investigated as possible amplifiers of regional drought phenomena.

Structure:

  1. Thermal power plants as artificial sources of atmospheric moisture: An underestimated role in the local water cycle

  2. The phase-out of coal and nuclear power: Reduction of steam clouds above power plants and their climatic consequences

  3. The deindustrialization of heavy industry: Loss of industrial evaporation areas and technical Moisture Inputs

  4. Strict environmental regulations and closed cooling systems: Reducing evaporative water processes in the name of water protection

  5. Meteorological observations in post-industrial areas: Correlations between power plant closures and local drought

  6. New perspectives for integrative water and climate management: Should technical moisture sources be included in planning?

 

1. Thermal Power Plants as Artificial Sources of Atmospheric Humidity: An Underestimated Role in the Local Water Cycle

Thermal power plants, especially coal-fired and nuclear power plants, make extensive use of water to cool their facilities. This water is usually taken from nearby rivers or lakes, undergoes the process of heat absorption, and is finally released back into the environment as heated water or in the form of steam—either directly into the waterways or into the atmosphere via giant cooling towers. These processes have beenThis has led to the formation of local fog, cloud formation, and increased humidity in the surrounding area for decades.

The amount of water released is immense. A medium-sized nuclear power plant, for example, can emit several million liters of water into the atmosphere every day, some of which evaporates and thus directly influences atmospheric humidity. Coal-fired power plants with open cooling systems or wet cooling towers also constantly release evaporated water into the ambient air. Over decades, this resulted in an anthropogenically enhanced local water cycle, which, although it had only a small global effect, was certainly noticeable at the regional level.

In regions with dense power plant infrastructure – In areas such as the Rhineland or the Ruhr region, these water vapor inputs contributed to a microclimate characterized by higher humidity, increased fog formation, and slightly increased local precipitation. This effect has rarely been quantified or taken into account in climate models, as it was often considered "insignificant" compared to global climate factors. However, the local hydrological implications of these systems were real - and are now gradually disappearing.

2. The phase-out of coal and nuclear power: Reduction of steam clouds above power plants and their climatic consequences

With the politically enforced dismantling of coal and nuclear power plants - Particularly in German-speaking countries, not only are emission sources of CO₂ and radioactive residues disappearing, but also continuous anthropogenic sources of water vapor. Germany's nuclear phase-out by 2023 and the planned coal phase-out by 2038 at the latest will lead to the disappearance of hundreds of cooling towers, evaporators, and open-loop systems that have been part of a stable regional water cycle for decades.

These power plants generated not only electricity but also heat in the form of steam clouds, which were particularly visible as white plumes above the cooling towers during cold months. These artificially created clouds formed from condensing water vapor, which, under certain atmospheric conditions, could contribute to the formation of cumulus clouds or light localized rainfall. Furthermore, these vapor clouds continuously supplied the lower troposphere with moisture, which was particularly important in continental European regions with already limited access to ocean moisture.

The dismantling of these systems will lead to a decoupling of technical and atmospheric moisture flows. The loss of this moisture input leads to faster soil drying, particularly in summers with little rainfall, increased drought stress for plants, and increased heat effects, as less water is available for evaporation. In areas with a historically high density of power plants, these effects are already measurable, but have so far neither been systematically documented nor incorporated into water management planning processes.

3. The deindustrialization of heavy industry: Loss of industrial evaporation areas and technical moisture inputs

Parallel to the reduction in energy production, a profound structural change has been taking place in heavy industry since the 1990s. Foundries, steel mills, large chemical plants, and aluminum smelters—many of these operations were shut down, automated, or relocated abroad. These industries required not only enormous amounts of energy, but also vast quantities of cooling water, process water, and cleaning fluids, which were regularly evaporated in open circuits or released through air cooling.

Here, too, an anthropogenic humidity equilibrium developed over decades, often going unnoticed. Hot steel or coking plants generated continuous thermal updrafts, as did refineries or petrochemical plants. The evaporative emissions from such industries were fed by countless open basins, rivers, cooling systems, and hall ventilation systems. Overall, they led to an accumulation of atmospheric moisture—sometimes even in urban areas, where natural evaporation is already minimized by soil sealing.

Deindustrialization—often celebrated as a positive environmental success—thus also has unintended consequences for the microclimate.The elimination of industrial heat sources not only reduces pollutants, but also thermal convection and evaporation. Combined with the increasing sealing of urban areas and the decline of agricultural irrigation systems, this exacerbates atmospheric drying, particularly during the transitional periods between spring and summer.

4. Strict environmental regulations and closed cooling systems: Reducing evaporative water processes in the name of water protection

In recent decades, numerous laws and regulations have been enacted in Europe, and especially in Germany, to protect the environment and water bodies. The goal was to limit the warming of rivers, prevent the recirculation of pollutants, and increase the efficiency of technical processes. One consequence of these measures was the conversion of many cooling systems from open to closed circuits, in which water is reused multiple times and no longer evaporates.

Technically speaking, this means: instead of releasing hot exhaust air or wastewater into the environment, it is circulated internally, cooled, and reused. While this improves energy and resource use, it also reduces contact with the atmosphere – and thus the possibility of evaporation, heat dissipation, and moisture recirculation.

Rainwater retention basins and new drainage systems in cities are also now designed to lose as little water as possible to the atmosphere. Infiltration is preferred over evaporation – which seems ecologically sensible, but in the long term contributes to a decrease in humidity in urban microclimates. Especially in hot summers, this can lead to increased thermal stress because less latent evaporative cooling is available.

Overall, this creates a seemingly paradoxical effect: Environmental protection—especially of water bodies—through technical insulation leads to a decrease in natural and anthropogenic evaporation. This results in the loss of an important atmospheric moisture input that, in the past, stabilized not only the water balance but also local resilience to heat waves.

5. Meteorological observations in post-industrial areas: Correlations between power plant shutdowns and local drought

Initial meteorological analyses and long-term observations indicate that regions with strong deindustrialization and power plant dismantling have been experiencing an increase in dry periods for years – independent of global climate trends. These observations are particularly striking where many power plants were shut down in a short period of time, such as parts of eastern Germany, Saarland, or parts of northern Italy.

Satellite-based evaluations show that after the shutdown of large cooling systems, soil moisture decreases more quickly, the drying potential of the air increases, and the number of summer days with temperatures above 30°C has increased significantly. At the same time, relative humidity decreased in some areas, while evapotranspiration from vegetation also declined due to increasing aridity—a self-reinforcing effect.

The challenge lies in clearly quantifying these developments. Previous climate models barely or not at all consider the loss of anthropogenic evaporation sources. Meteorological services also do not establish a direct connection between power plant steam and microclimate. However, it is urgently necessary to establish new modeling approaches that consider technogenic moisture inputs as well as emissions and sealing.

6. New Perspectives for Integrative Water and Climate Management: Should Technical Moisture Sources Be Incorporated into Planning?

Against the backdrop of increasing drought, heat waves, and crop failures, it is becoming clear that a purely emissions-based understanding of environmental policy is no longer sufficient. What is needed is an integrative water and climate management that not only reduces emissions but also incorporates atmospheric moisture balances. Technically generated water vapor inputs—previously viewed as "unwanted side effects"—could be understood in the future as controlled climate elements.

Some pilot projects are already experimenting with evaporation ponds, urban mist spraying, or artificial irrigation forlocal humidity increase. The recommissioning of decommissioned cooling ponds – without electricity production – would also be conceivable in order to specifically generate evaporation during dry periods. Urban systems such as green roofs, open waterways, or semi-technical moisture sources (e.g., open cooling systems with a purification function) could also take on new roles.

However, a political and social paradigm shift is needed: away from the simple dogma of reduction and toward a differentiated assessment of technical processes – also considering their contribution to local humidity balance. Only if we consider both natural and anthropogenic water flows holistically can we create a resilient future in times of climate uncertainty.

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AUTHOR:  THOMAS JAN POSCHADEL

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