ABSTRACT:

Groundwater (GW) impacts water, energy, and carbon cycles by providing additional moisture to the root zone. Although the interactions of shallow GW and the terrestrial land surface are widely recognized, incorporating shallow GW into the land surface, climate, and agroecosystem models as a lower boundary condition is not yet possible due to the lack of groundwater data.
Here, we provide global maps of the terrestrial land surface areas influenced by shallow GW at daily timesteps. We derived this data using spaceborne soil moisture observations from NASA's SMAP satellite. We used the Level-2 enhanced passive soil moisture (L2_SM_P_E) product to detect shallow GW signals. The presence of shallow GW is obtained using an ensemble machine learning model. The model is trained using results from global simulations. We published the details of our approach in a separate research paper (Soylu and Bras, 2022 - https://ieeexplore.ieee.org/document/9601254).
Our data covers the period from mid-2015 to 2021 (a separate NetCDF file for each year) with a 9 km spatial resolution, the same as the SMAP "Equal Area Scalable Earth" (EASE) grids.

Reference:
Soylu, M.E, and Bras, R.L. "Global Shallow Groundwater Patterns From Soil Moisture Satellite Retrievals." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 15 (2022): 89-101