Decreasing rainfall and increasing evapotranspiration due to climate change are among the main pressures that affect the availability of groundwater resources, especially in karst areas. Around 25% of the global population receives drinking water from karst aquifers. In many semi-arid regions, karst springs are often the only accessible freshwater source and their karst groundwater are mostly sensitive to hydrological changes related to modification of rainfall patterns, particularly during droughts. It is evident how critical is to improve knowledge of karst aquifers recharge for managing and preserving their resources. In a framework of rising temperatures and change in the rainfall regime, occult precipitation represents a further atmospheric moisture sources available as support to the local hydrological budget at regional scale. This process occurs naturally in different environments around the World when air humidity is high and its condensation forms water droplets. Although these precipitations are not detected by standard rain gauges, it is considered an additional water input relevant for groundwater dependent ecosystems. In this study, the contribution of the occult precipitation to the hydrogeological balance of the gypsum karst of Sorbas (a semi-arid zone in Southern Spain) has been investigated analysing water stable isotope signature of rain, springs, cave drippings and condensation of atmospheric vapour within karst systems coupled with meteorological data. The results show that favourable conditions for occult precipitations occur seasonally, starting from summer and continuing until December. In this period, the ephemeral water input to the karst aquifer recharge has been estimated to be a significant proportion of groundwater, sustaining the hydrological baseflow during the hot and dry season.
The contribution of occult precipitation to karst aquifers recharge in semi-arid zones
Laura Sanna
2023
Abstract
Decreasing rainfall and increasing evapotranspiration due to climate change are among the main pressures that affect the availability of groundwater resources, especially in karst areas. Around 25% of the global population receives drinking water from karst aquifers. In many semi-arid regions, karst springs are often the only accessible freshwater source and their karst groundwater are mostly sensitive to hydrological changes related to modification of rainfall patterns, particularly during droughts. It is evident how critical is to improve knowledge of karst aquifers recharge for managing and preserving their resources. In a framework of rising temperatures and change in the rainfall regime, occult precipitation represents a further atmospheric moisture sources available as support to the local hydrological budget at regional scale. This process occurs naturally in different environments around the World when air humidity is high and its condensation forms water droplets. Although these precipitations are not detected by standard rain gauges, it is considered an additional water input relevant for groundwater dependent ecosystems. In this study, the contribution of the occult precipitation to the hydrogeological balance of the gypsum karst of Sorbas (a semi-arid zone in Southern Spain) has been investigated analysing water stable isotope signature of rain, springs, cave drippings and condensation of atmospheric vapour within karst systems coupled with meteorological data. The results show that favourable conditions for occult precipitations occur seasonally, starting from summer and continuing until December. In this period, the ephemeral water input to the karst aquifer recharge has been estimated to be a significant proportion of groundwater, sustaining the hydrological baseflow during the hot and dry season.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
