Gnann et al. (2026) On Utilizing Spatial Gradients to Discover Functional Relationships in Hydrology

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Water Resources Research
• Year: 2026
• Date: 2026-02-25
• Authors: Sebastian Gnann, Thorsten Wagener
• DOI: 10.1029/2025wr040101

Research Groups

Not specified in the abstract.

Short Summary

This paper reviews functional relationships in hydrology, defining them as variable relationships characterizing hydrological system functions along environmental gradients, and discusses their critical value for advancing hydrological theory, improving observational data, and enhancing computational models.

Objective

• To review and discuss the value of functional relationships in hydrology, particularly in the context of increasing data availability, for advancing hydrological theory, guiding observational data improvements, and serving as a tool for hydrological applications and computational models.

Study Configuration

• Spatial Scale: Broad, encompassing various hydrological systems across spatial gradients, leveraging "across different systems in space" and "at scales... of unprecedented size."
• Temporal Scale: Variable, depending on the specific functional relationships reviewed; the review itself reflects current understanding.

Methodology and Data

• Models used: No specific computational models were used in this review; "computational models" are discussed as an application area. "Perceptual models" are mentioned as a form of domain knowledge.
• Data sources: Scientific literature (for the review), in situ data, spatial data products, and domain knowledge (including perceptual models).

Main Results

• Functional relationships are defined as relationships between two or more variables that characterize hydrological system functions, emerging along dominant environmental or anthropogenic gradients.
• The paper reviews selected functional relationships from the literature, representing a variety of hydrological functions and spatial gradients.
• It highlights their value for hydrology in three key areas:
  1. As central building blocks for hydrological theory and process explanations.
  2. As a guide for improving observational data sets by focusing on associated gradients.
  3. As a tool for hydrological applications, particularly computational models.

Contributions

• Provides a conceptual framework and definition for functional relationships in hydrology.
• Synthesizes existing knowledge on functional relationships across various hydrological functions and spatial gradients.
• Articulates the multifaceted value of functional relationships for integrating theory, data, and models in hydrology.
• Proposes a renewed focus on these relationships and their associated gradients as a pathway to advance the field.

Funding

Not specified in the abstract.

Citation

@article{Gnann2026Utilizing,
  author = {Gnann, Sebastian and Wagener, Thorsten},
  title = {On Utilizing Spatial Gradients to Discover Functional Relationships in Hydrology},
  journal = {Water Resources Research},
  year = {2026},
  doi = {10.1029/2025wr040101},
  url = {https://doi.org/10.1029/2025wr040101}
}