Water is one of the key elements controlling cave microclimate, as it influences both temperature and humidity in underground environments. Its presence, in either liquid or solid form, interacts with the surrounding rock and cave air, altering their thermal balance. Water moves through the subsurface by following rock discontinuities, either as slowly percolating seepage water or as more substantial underground flows, such as primary or secondary karst conduits. It may also accumulate to form lakes of various sizes, or to completely fill cavities and fractures in deeper saturated karst zones and sumps. Near cave entrances, water can be found as accumulations of snow (snow pits) or ice (underground glaciers). In summary, water plays a decisive role in controlling the local thermal conditions and humidity levels in caves, regulating the transfer of heat between the interior of mountain massifs and the outer environment.

Water has a high heat capacity, warming up and cooling down much more slowly than air. For this reason, its presence tends to dampen daily and seasonal temperature fluctuations in the underground environment. However, in caves with permanent watercourses, thermal fluctuations may be stronger and more rapid, depending on the seasonal hydrological regime of the karst conduit.

Climate change directly affects the hydrological regime of caves by altering the amount and timing of water input, including, in mountain environments, the inflows related to melting of the snow cover. An increase in extreme rainfall events can intensify water flow in caves, leading to sudden changes in the micro-climate equilibrium. Conversely, prolonged drought periods reduce the water recharge into karst massifs, making them more sensitive to external climatic variations.

Beyond its direct effects on temperature of rock masses, the distribution of underground water also influences the capacity of caves to act as long-term climate archives. Caves containing ice or snow deposits represent natural records of climatic trends over decades or centuries. The study of these deposits allows researchers to understand how underground environments respond to global climate change.

Water therefore represents a key element in the delicate balance governing the underground climate, influencing temperature, humidity and the capability of caves to preserve ice or snow deposits. Understanding water dynamics not only helps us to better interpret the effects of climate change in the recent past, but also provides a valuable tool for monitoring ongoing transformations and predicting the future evolution of these unique environments.