Also known as
Model type Single
Model part of larger framework
Incorporated models or components:
Spatial dimensions 2D
Spatial extent Global, Continental, Regional-Scale, Landscape-Scale, Watershed-Scale
Model domain Terrestrial, Hydrology, Coastal, Ecosystems, Cryosphere
One-line model description A watershed delineation model based on hexagonal mesh grid
Extended model description HexWatershed is a C++ program to define flow direction and other watershed characteristics at regional to global scale. The unique feature of HexWatershed is that it uses a hexagon and hexagon-alike unstructured mesh. Because of that, it have many advantages:
  • It can represent adjacency uniformly
  • It eliminates ``island effect due to the differences in D4 and D8 neighbor definitions
  • It can effectively represent a spherical topology such as Earth

Watershed delineation, Unstructured, hydrology, flow routing, Hexagon,

First name Chang
Last name Liao
Type of contact Model developer
Institute / Organization Pacific Northwest National Laboratory
Postal address 1
Postal address 2
Town / City Richland
Postal code 99354
State Washington
Country United States
Email address

Supported platforms Unix, Linux, Mac OS
Other platform
Programming language C++
Other program language
Code optimized Single Processor, Multiple Processors
Multiple processors implemented Shared memory
Nr of distributed processors
Nr of shared processors 20
Start year development 2017
Does model development still take place? Yes
If above answer is no, provide end year model development
Code development status Active
When did you indicate the 'code development status'? 2020
Model availability As code, As teaching tool
Source code availability
(Or provide future intension)
Through web repository
Source web address
Source csdms web address
Program license type GPL v3
Program license type other
Memory requirements Depend on study domain and spatial resolution
Typical run time Depend on study domain and spatial resolution, a few minutes for a typical watershed.

Describe input parameters DEM raster and Hexagon shapefile, stream segment threshold
Input format ASCII
Other input format Input and output workspace, etc.
Describe output parameters Hexagon DEM, flow direction, flow accumulation, stream grid, stream segment, stream order, stream confluence, subbasin, watershed boundary, etc.
Output format ASCII, Binary
Other output format NetCDF and VTK
Pre-processing software needed? Yes
Describe pre-processing software QGIS may be needed to generate the hexagon mesh grid shapfile.
Post-processing software needed? No
Describe post-processing software
Visualization software needed? Yes
If above answer is yes ESRI
Other visualization software VisIt if use the version 2.0

Describe processes represented by the model DEM resampling;

Depression filling; Flow direction; Flow accumulation;

Describe key physical parameters and equations Terrain analysis.

One equation is the resolution of a hexagon can be estimated using its area instead of edge length.

Describe length scale and resolution constraints It is best performance for high resolution (<100m) simulation.

With the version 2.0, coarser resolution is supported through stream burning feature.

Describe time scale and resolution constraints None
Describe any numerical limitations and issues

Describe available calibration data sets National Hydrography Dataset (NHD) flowline datasets were used to evaluated the model.
Upload calibration data sets if available: Media:Please refer to the paper
Describe available test data sets
Upload test data sets if available:
Describe ideal data for testing

Do you have current or future plans for collaborating with other researchers? Yes, I plan to use this model with other hydrology models, both regional and global scale.
Is there a manual available? Yes
Upload manual if available: Media:The manual will soon available online
Model website if any
Model forum / discussion board We currently use Github issue for discussion.


This part will be filled out by CSDMS staff

OpenMI compliant
BMI compliant
WMT component
PyMT component
Is this a data component
Can be coupled with:
Model info
Citation indices HexWatershed
Nr. of pubs: 1
Citations: 0
h-index: --"--" is not a number.




Citation indices HexWatershed
Nr. of pubs: 1
Citations: 0
h-index: --"--" is not a number.

Featured publication(s)YearModel describedType of ReferenceCitations
Liao, Chang; Tesfa, Teklu; Duan, Zhuoran; Leung, L. Ruby; 2020. Watershed delineation on a hexagonal mesh grid. Environmental Modelling &amp; Software, 128, 104702. 10.1016/j.envsoft.2020.104702
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Model overview 0
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Input Files

Output Files