Coastal GroundWater Level (CGWL) Dataset

The CGWL (Coastal Groundwater Level) dataset provides harmonized in situ groundwater level observations for wells in coastal regions, associated well metadata, derived summary statistics, and spatially aggregated products (H3 grids and HydroBASINS). The dataset also includes references to original data providers.

Variable definitions, units, sign conventions, and file formats are documented in: Metadata_CGWL.pdf

Repository Structure

• 01_Time_Series – Groundwater level time series (weekly, monthly, annual) in standardized formats.
• 02_Statistics – Summary statistics per time series (e.g., availability, mean, median, min, max).
• 03_Wells – Well metadata (locations and attributes).
• 04_References – Attribution and copyright information for original data sources.
• 05_Grids – H3 hexagonal grids (resolutions 6 and 8; Uber Technologies Inc., 2024) covering CGWL well locations.
• 06_Gridded_Groundwater – H3-based gridded median groundwater depth and groundwater elevation derived from time series data.
• 07_HYBAS – HydroBASINS level-12 watersheds (HYBAS-12; Lehner and Grill, 2013) covering CGWL well locations.
• 08_Gridded_Groundwater – HYBAS-12 aggregated median groundwater depth and groundwater elevation derived from time series data.

Related publication:

For details on dataset complilation, processing choices, and example applications, see Nolte et al. 2026.

Citation Requirement

When using this dataset, please reference:

1. This repository (dataset version used), and
2. The original data publishers (see copyright details in 04_References/references.csv)

Please also cite Nolte et al. 2026 for methods, processing choices, and example applications.

References:

Lehner, B. and Grill, G.: Global river hydrography and network routing: baseline data and new approaches to study the world's large river systems, Hydrological Processes, 27, 2171–2186, doi:10.1002/hyp.9740, 2013.

Uber Technologies Inc: H3: Hexagonal hierarchical geospatial indexing system, https://h3geo.org/, 2024.

Nolte, A., Bender, S., Hartmann, J., Baltruschat, S., Moosdorf, N. and Reinecke, R.: Coastal groundwater-level trends reveal global susceptibility to seawater intrusion, Nature Water, doi:10.1038/s44221-026-00619-8, 2026.

Licensing

This dataset is licensed under the Creative Commons Attribution Non Commercial 4.0 International license (CC BY-NC 4.0).

Disclaimer

This dataset is provided “as is”. While it was compiled with great care, no warranty is given regarding correctness or completeness.

Contact

For questions regarding this dataset, please contact the corresponding author as listed in Nolte et al. (manuscript under review).