Caves as observatories of groundwater recharge

Groundwater recharge is the downward flow of water reaching the water table. Recharge can occur through the soil from rainfall, and from losing or ‘leaking’ rivers, lakes and wetlands. 

Understanding when recharge occurs is of fundamental importance for our understanding of the sustainability of groundwater resources e.g. for water resource allocation, protection of groundwater supplies and the sustainability of dryland farming and irrigated agriculture.

However, recharge is difficult to measure. For example, most groundwater level measurements and water samples are obtained via wells 

(or bores) which integrate all possible recharge sources and multiple events, including water level changes of ‘fossil’ groundwater.

Caves provide a valuable window into the groundwater recharge process. By entering a cave, you a walking into the unsaturated zone, the region between the Earth’s surface and the water table. Water passing through the caves provides evidence of recharge occurring. Stalagmites in the caves provide archives of groundwater recharge in the past.

The Connected Waters Initiative team is the world-leading group using caves as observatories of groundwater recharge. Led by Andy Baker and his lab group, they collaborate with teams at ANSTO (Pauline Treble group), Freiburg (Andreas Hartmann group), Lausanne (Gregoire Mariethoz group), Cardiff (Mark Cuthbert group), and individual research leaders including at the Max-Planck Institute (Monika Markowska), University of Reading (Laia Comas-Bru) and Chinese Academy of Sciences (Wuhui Duan). 

21.04.2020. Our display for the EGU General Assembly 2020 is now published for interactive comment. “Insights into recharge processes and speleothem proxy archives from long-term monitoring networks of cave drip water hydrology” can be read and commented on at: (open access)

20.02.2020. Our collaboration with the Hartmann group has led to this paper led by Romane Berthelin. “A soil moisture monitoring network to characterize karstic recharge and evapotranspiration at five representative sites across the globe” is available at (open access)

02.01.2020. Interested in how to interpret stalagmite oxygen isotope records as a record of groundwater recharge in water-limited environments? Here's a modern calibration study led by Monika Markowska. “Modern speleothem oxygen isotope hydroclimate records in water-limited SE Australia” is available at this location:

01.10.2019. The wonderful team at the UNSW Global Water Institute have produced this article on “Understanding connections between groundwater, caves and climate”

24.09.2019. You can check out the latest Water Underground blog on "Groundwater and a 'green drought'" here: (all blog articles are double peer reviewed and hosted by the AGU and EGU)

05.07.2019. We use meta-analysis and modelling to reveal that cave drip water oxygen isotope composition is determined by the recharge-weighted rainfall oxygen-isotope composition. “Global analysis reveals climatic controls on the oxygen isotope composition of cave drip water” can be accessed here (open access)

09.10.2018. Its rained! But is it enough? What is the difference between rainfall drought and groundwater drought? You can read the latest Water Underground blog article “groundwater and drought” here: (all blo

g articles are double peer reviewed and hosted by the AGU and EGU)

14.02.2018. Kashif Mahmud has published his final PhD paper, another that investigates the hydrological controls of cave drip water hydrology. “Hydrological characterization of cave drip waters in a porous limestone” is published here: (open access)

12.08.2017. “Modelling karst vadose zone hydrology and its relevance for paleoclimate reconstruction” by Andreas Hartmann and Andy Baker is our new publication in Earth-Science Reviews. You can read it here: (accessible version at

14.06.2017. Interested in groundwater recharge in the Last Glacial Maximum in the Flinders Ranges? Pauline Treble leads this paper, reporting the evidence for recharge from two stalagmites. “ Hydroclimate of the Last Glacial Maximum and deglaciation in southern Australia’s arid margin interpreted from speleothem records (23–15 ka) can be read here: (open access)

03.11.2016. Watching trees drink the groundwater. Katie Coleborn leads a paper that shows how cave drip loggers reveal the subsurface water use of trees, and that it is mostly observed after hot summer afternoons. “Solar-forced diurnal regulation of cave drip rates via phreatophyte evapotranspiration” can be read here: (open access)

20.01.2016. Can you estimate the amount of recharge in caves using a combination of lidar mapping of drip sources and drip count data? Kashif Mahmud leads a paper that explains how. “Estimation of deep infiltration in unsaturated limestone environments using cave lidar and drip count data” can be read here: (open access)

08.01.2016. You can use lidar mapping to count and classify stalactites and other drip water sources in cave. The important first-step to quantify groundwater recharge into caves is explained by Kashif Mahmud. “Terrestrial LiDAR survey and morphological analysis to identify infiltration properties in the Tamala Limestone, Western Australia” is available here: (accessible version at