Research

Research and publications

My research asks how water moves through landscapes, how we can observe it reliably, and how that knowledge can be turned into data and evidence that institutions can use. It combines process-based hydrology, large-sample analysis and international data infrastructure.

Featured · Scientific Data, 2020

WoKaS: the first global open database of karst spring discharge

Karst aquifers supply drinking water to a large part of the world's population, yet their behaviour was hard to compare because observations were scattered across literature, agencies and research groups. WoKaS brings these records together, harmonised and openly available, so that researchers and water managers can learn from karst systems in contrasting climates.

400+ springs · open data · peer-reviewed in Scientific Data

Read the paper

Olarinoye, T., Gleeson, T., Marx, V., et al. (2020). Global karst springs hydrograph dataset for research and management of the world's fastest-flowing groundwater. Scientific Data, 7, 59.

Research themes

Areas of focus

Research area	Focus
Groundwater	Climate and global-change impact assessment, karst and aquifer dynamics
Hydrological modelling	Water balance, hydrological processes and recession analysis
Soil moisture	In-situ networks, monitoring and validation
Hydroclimatic data	Climate and hydrological observations, large-sample data analysis
Earth observation	Satellite hydrology and ground-based validation
Water information systems	Data infrastructure, integration, quality control and accessibility
Climate resilience	Water security, drought and environmental change

Research and projects

Roles, contributions and outputs

Water information systems · Groundwater

World Karst Spring Hydrographs (WoKaS)

Role Lead · 2018–2020

Compiled the first global open database of karst spring discharge from literature, hydrological databases and researchers worldwide, giving hydrologists a common basis to compare how karst aquifers behave in different climates.

Contributions

Led data collection, harmonisation and quality control.
Designed the dataset for open, reusable research and management use.

Key outputs 400+ springs; published in Scientific Data (2020), the primary reference for comparative karst research.

Read the paper

Soil moisture · Hydroclimatic data

Soil moisture monitoring and global observation networks

Role Scientific Officer, data acquisition and products · 2021–present

The International Soil Moisture Network (ISMN) is a global hub for in-situ soil moisture observations, with data collection, harmonisation, advanced quality control and free, FAIR access. It is widely used to validate satellite and model products.

Contributions

Acquire and process data from the international provider network and develop new data products.
Lead outreach, user and provider engagement, and communication.
Organise community events: an EGU data-services session, an annual splinter meeting and a virtual provider workshop series.

Key outputs As presented at IAHS 2025, more than 80 data providers and 3,000 stations, with time series from 1952 to near real time.

Visit ISMN

Water information systems

Hydrological data integration and information systems

Role Science and data-services development · 2021–present

Work on how global hydrological data centres and networks can be better connected and communicated, so that data services serve research, monitoring and water management together.

Contributions

Initiated and led a cross-institutional EGU session with ISMN, GRDC, GWDC, IGRAC and GTN-H as co-conveners (2023).
Contributed to a catalogue of six decades of German contributions to hydrology and the UNESCO International Hydrological Programme.

Key outputs A recurring forum for hydrological data services and new links between global data centres.

Hydrological modelling · Climate resilience

Hydroclimatic processes and water resources

Role First author · 2019–2022

Developed objective, automated methods to separate and classify the fast (conduit) and slow (matrix) components of spring recession, and tested them on large samples of hydrographs across contrasting climates.

Contributions

Built automated recession extraction and parameter estimation for large-sample analysis.
Extended the approach with uncertainty-aware, variable-matrix-fraction recession analysis (in review).

Key outputs Replaces manual, subjective analysis and makes large-sample studies feasible (HESS, 2022).

Read the paper

Climate resilience · Groundwater

Groundwater under urbanisation and climate change, Arusha

Role Lead author · 2017–2018

Explored how urban growth and climate change jointly affect groundwater resources in a fast-growing East African city, with partners from Tanzania and the Netherlands.

Contributions

Water-balance and scenario assessment under land-use and climate change.
Field mapping and ground-truthing of satellite-derived land-use maps.

Key outputs Published in Water International (2020).

Read the paper

Climate resilience · International cooperation

Transboundary river cooperation

Role Co-author · 2026

Quantified the trade-off between upstream hydropower generation and downstream water demand under climate change, identifying where both sides can gain.

Key outputs Published in the Journal of Hydrology (2026).

Read the paper

Further project participation

Since 2018 Global assessment of water stress in karst regions in a changing world (GloW)
2017 Experimenting with practical Transitional Groundwater Management Strategies for the Urban Poor in Sub-Saharan Africa (T-GroUP)
2016 Mitigating groundwater salinity impacts for improved water security in coastal areas under socio-economic and climate change (SALINPROVE)

Scientific publications

Peer-reviewed output

Names in bold mark my contributions. Citation counts and the full record are available through my profiles.

Frank Kaspar, Simon A. Mischel, Stephan Dietrich, Lena Fay Boehmer, Moritz Heinle, Rainer Hollmann, Tunde Olarinoye, Hannes Konrad, Wolfgang Korres, Dmytro Lisniak et al. (2026). Beiträge zur Beobachtung des globalen Wasserkreislaufs. Warnsignal klima: Die Landwirtschaft, Wissenschaftliche Auswertungen - in Kooperation mit GEO, Hamburg, Hamburg, pp. 50-56.

The book chapter describes the activities of the water-related international data centres in Germany and provides an insight into key contributions based on satellite data. Limitations in data availability and quality are discussed.

DOIOpen access
Abraham, T., Olarinoye, T., Hartmann, A., Hendricks Franssen, H.J., Liu, Y. (2026). Towards cooperation on transboundary rivers: achieving a win–win balance between upstream hydropower generation and downstream water demand under climate change. Journal of Hydrology.

Shows how upstream hydropower and downstream water demand can be balanced under climate change, a basis for cooperation between riparian countries.

DOI
Berthelin, Romane, Olarinoye, Tunde, Rinderer, Michael, Mudarra, M., Demand, Dominic, Scheller, Mirjam, Hartmann, Andreas (2023). Estimating karst groundwater recharge from soil moisture observations – a new method tested at the Swabian Alb, southwest Germany. Hydrology and Earth System Sciences, 27. 385-400.

Estimates karst groundwater recharge from soil moisture observations.

DOIOpen access
Olarinoye, T., Gleeson, T., Hartmann, A. (2022). Karst spring recession and classification: efficient, automated methods for both fast- and slow-flow components. Hydrology and Earth System Sciences, 26, 5431–5447.

Objective, automated methods that separate and classify fast and slow flow in spring hydrographs, making large-sample studies feasible.

DOIOpen access
Olarinoye, T. (2022). Unravelling the hydrodynamic behavior of karst aquifer systems through comparative hydrology. Ph.D. thesis, University of Freiburg.
Hartmann, A., Liu, Y., Olarinoye, T., Berthelin, R., Marx, V. (2021). Integrating field work and large-scale modeling to improve assessment of karst water resources. Hydrogeology Journal, 29, 315–329.

Combines fieldwork with large-scale modelling for more reliable assessment of karst water resources.

DOIOpen access
Olarinoye, T., Foppen, J. W., Veerbeek, W., Morienyane, T., Komakech, H. (2020). Exploring the future impacts of urbanization and climate change on groundwater in Arusha, Tanzania. Water International.

Scenario assessment of how urban growth and climate change together affect groundwater in a fast-growing East African city.

DOI
Olarinoye, T., Gleeson, T., Marx, V., et al. (2020). Global karst springs hydrograph dataset for research and management of the world's fastest-flowing groundwater. Scientific Data, 7, 59.

WoKaS, the first global open database of karst spring discharge, built from literature, hydrological databases and researchers worldwide.

DOIOpen access

Submitted / in review

Mirgol, B., Dogulu, N., Dieppois, B., Olarinoye, T., et al. (in review). Artificial intelligence and machine learning in hydrology: global perspectives on adoptions, trust, challenges, and future directions. Nature Communications (in review).
In review
Olarinoye, T., Rinderer, M., Gleeson, T., Hartmann, A. (in review). Redefining karst hydrograph recession analysis; introducing variable matrix fractions and parameters uncertainty. Water Resources Research (in review), preprint.
DOIIn review

Interested in joint research?

I am open to collaboration with universities, research institutes and scientists working on groundwater, soil moisture and hydrological data.

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