Shen et al. (2026) Network-based subbasin-scale mapping of streamflow alteration in Ontario, Canada

Identification

• Journal: Earth system science data
• Year: 2026
• Date: 2026-11-02
• Authors: Hongren Shen, Bryan A. Tolson, James Richard Craig, Robert A. Metcalfe, Jonathan Romero-Cuéllar, Jamie Luce
• DOI: 10.5194/essd-18-7915-2026

Research Groups

• Department of Civil and Environmental Engineering, University of Waterloo, Ontario, Canada
• Environmental and Life Sciences Graduate Program, Trent University, Ontario, Canada
• Aquatic Research and Monitoring Section, Ministry of Natural Resources, Trent University, Ontario, Canada

Short Summary

This study introduces the Streamflow Alteration Index (SAI), a parsimonious, network-based screening metric, to map and quantify potential streamflow alteration across Ontario, Canada. The resulting SAI v1.0 database provides a practical and reproducible baseline for large-domain hydrologic and ecological applications by estimating the percentage of upstream drainage area exposed to alteration sources.

Objective

• To develop and evaluate the Streamflow Alteration Index (SAI) as a parsimonious, network-based screening metric for mapping and quantifying potential streamflow alteration from instream structures (dams, reservoirs, waterpower facilities, lockstations) across large domains, specifically Ontario, Canada.

Study Configuration

• Spatial Scale: Province-wide (Ontario, Canada), subbasin-scale mapping (average subbasin area of 4.3 km²), river-reach layers.
• Temporal Scale: The SAI v1.0 database provides a static screening baseline; evaluation used hydrometric data from 1990–2024.

Methodology and Data

• Models used: Streamflow Alteration Index (SAI) framework, a network-based screening metric that uses drainage-area-weighted mixing and a first-order drainage-area scaling approximation. It comprises two independent indices: SAII (for confirmed Level I alteration sources) and SAIII (for potential Level II alteration sources).
• Data sources:
  • Ontario Lake and River Routing Product Version 2 (OLRRP v2) for network topology and subbasin/lake attributes.
  • Ontario Dam Inventory (ODI) (1803 records).
  • Ontario Ministry of Natural Resources (MNR) operated dam dataset (389 records).
  • Waterpower Generation Stations dataset from Ontario MNR (211 records).
  • Digitized lockstations (73 records) from Trent-Severn Waterway, Rideau Canal, and Welland Canal.
  • Hydrometric gauges from Water Survey of Canada (WSC) (488 retained for evaluation).
  • Reference Hydrometric Basin Network (RHBN) gauges (148 retained for evaluation).
  • HydroLAKES database (for OLRRP v2 lake polygons).
  • Satellite imagery and online basemaps for geospatial alignment and verification.

Main Results

• A total of 2476 infrastructure records were retained after geospatial alignment and screening from an initial 2528.
• 643 unique subbasins were identified as containing Level I and/or Level II alteration signal sources.
• The SAI v1.0 database provides province-wide subbasin and river-reach layers for screening potential instream alteration.
• SAI classified 86 % of 148 Reference Hydrometric Basin Network (RHBN) natural gauges as natural, with no RHBN gauges classified as altered.
• SAI classified 86 % of 125 additional Water Survey of Canada (WSC) natural gauges as natural.
• Among 215 WSC-regulated gauges, SAI classified 26 % as altered, 40 % as conditional, and 34 % as natural, highlighting differences between binary agency labels and the SAI framework.
• The SAI v1.0 dataset is publicly available from Zenodo (https://doi.org/10.5281/zenodo.19547932).

Contributions

• Introduces the Streamflow Alteration Index (SAI), a novel, parsimonious, network-based screening metric for large-domain streamflow alteration assessment.
• Provides a practical, transparent, and reproducible screening baseline for hydrologic and ecological applications without requiring detailed operating rules.
• Develops the SAI v1.0 database for Ontario, offering province-wide subbasin and river-reach layers for screening potential instream alteration at both gauged and ungauged locations.
• Addresses limitations of traditional metrics by explicitly representing downstream propagation and dilution of alteration signals through a river network.
• Incorporates uncertainty by using paired indices (SAII for confirmed, SAIII for potential sources) and a three-class scheme (natural, conditional, altered) for classification.

Funding

• 2022–2026 Collaborative Research Agreement between the Ontario Ministry of Natural Resources and the University of Waterloo.
• Supported Hongren Shen’s research appointment.

Citation

@article{Shen2026Networkbased,
  author = {Shen, Hongren and Tolson, Bryan A. and Craig, James Richard and Metcalfe, Robert A. and Romero-Cuéllar, Jonathan and Luce, Jamie},
  title = {Network-based subbasin-scale mapping of streamflow alteration in Ontario, Canada},
  journal = {Earth system science data},
  year = {2026},
  doi = {10.5194/essd-18-7915-2026},
  url = {https://doi.org/10.5194/essd-18-7915-2026}
}