Model:EcoTWIN

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EcoTWIN


Metadata

Also known as
Model type Single
Model part of larger framework
Note on status model
Date note status model
Incorporated models or components:
Spatial dimensions 2D
Spatial extent Regional-Scale, Landscape-Scale, Watershed-Scale
Model domain Terrestrial, Hydrology
One-line model description A fully distributed, tracer-aided ecohydrological model that simultaneously simulates water, stable-isotope, and nitrogen fluxes.
Extended model description EcoTWIN (ECOhydrological model that Tracks Water, Isotopes, and Nutrients) is a C++ ecohydrological framework that couples hydrological, stable-isotope (²H, ¹⁸O), and nitrogen modules to jointly simulate water, isotope, and nutrient fluxes from canopy to groundwater. It follows a distributed, multi-layer, top-down bucket-type structure with selectable process conceptualizations (drawing on EcoPlot, EcH2O, and mHM for hydrology; EcH2O-iso for isotopic mixing/Craig-Gordon fractionation; and HYPE/mHM-Nitrate for nitrogen cycling), and supports dynamic re-parameterization of spatial discretization (e.g., to reflect land-use change) at user-defined timesteps. Aided by tracer simulations, the model computes spatially and temporally explicit water ages and travel times, linking catchment hydrology to water-quality/biogeochemical processing. It was calibrated and validated against discharge, in-stream isotopes, and NO3–N concentrations (1980–2024) in 17 large European catchments spanning Alpine-to-lowland and snow-dominated-to-Mediterranean gradients, and cross-checked against ERA5 snow depth, MODIS evapotranspiration, and GRACE surface-water-anomaly products for uncalibrated internal fluxes.
Keywords:

ecohydrology, tracer-aided modeling, stable water isotopes, nitrogen/water quality modeling,

Name Songjun Wu
Type of contact Model developer
Institute / Organization Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB)
Postal address 1
Postal address 2
Town / City Berlin
Postal code 12587
State
Country Germany
Email address mailto:songjun.wu@igb-berlin.de
Phone
Fax


Name Doerthe Tetzlaff
Type of contact Project manager
Institute / Organization IGB Leibniz Institute Berlin
Postal address 1
Postal address 2
Town / City Berlin
Postal code
State
Country Germany
Email address d.tetzlaff@igb-berlin.de
Phone
Fax


Supported platforms
Linux
Other platform
Programming language

C++, Python

Other program language
Code optimized Single Processor
Multiple processors implemented
Nr of distributed processors
Nr of shared processors
Start year development 2025
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'? 2026
Model availability As code
Source code availability
(Or provide future intension) 		Through web repository
Source web address https://github.com/songjun-wu/EcoTWIN
Source csdms web address
Program license type GPL v3
Program license type other
Memory requirements --
Typical run time --


Describe input parameters Gridded GIS layers (DEM, flow direction, slope, channel width/length, land-use fractions, soil-type fractions, depth-dependent soil properties), climatic forcing (precipitation, air temperature, potential ET, relative humidity; optionally air pressure, net radiation, wind speed for channel evaporation), and — for nitrogen simulation — fertilization maps and rainfall nitrate concentration. Configuration is via config.ini (paths, module on/off switches, process-conceptualisation choices, I/O sections) and param.ini (parameter values); a template is provided in the configs/ folder. Reference application used 5 km² grid resolution, daily timestep, 1980–2024 (2-year spin-up).
Input format ASCII, Binary
Other input format
Describe output parameters User-selectable fluxes/states (discharge, isotopic composition, NO3–N concentration, canopy/soil/groundwater storages, water ages and travel times), specified in the "Reports" section of config.ini
Output format Binary
Other output format
Pre-processing software needed? No
Describe pre-processing software
Post-processing software needed? No
Describe post-processing software
Visualization software needed? No
If above answer is yes
Other visualization software


Describe processes represented by the model Hydrological: canopy interception/throughfall, snow accumulation/degree-day melt, Green–Ampt infiltration, three alternative percolation schemes (incl. SWAT- and mHM-style), soil evaporation/transpiration partitioning by root fraction, groundwater recharge, irrigation extraction, and lateral/channel routing (kinematic-wave approximation). Isotopic: conservative mixing plus Craig–Gordon fractionation during evaporation; explicit tracking of water ages/travel times. Nitrogen: nitrification/denitrification (constrained by a Damköhler-number proof of concept) and transport based on HYPE and mHM-Nitrate conceptualisations.
Describe key physical parameters and equations Water balance equations for canopy, soil layers, unsaturated zone and groundwater (Eqs. 1–18 in the paper); infiltration via Green–Ampt with Newton–Raphson solution; percolation via three alternative schemes (linear, Ks-weighted, exponential/mHM-style); Craig–Gordon isotopic fractionation for evaporation; Damköhler-number-based nitrogen transformation kinetics. Full parameter list in the paper's Table S1 (Supplement).
Describe length scale and resolution constraints Applied at 5 km² grid resolution over catchments of 10³–10⁵ km²; distributed structure is scale-flexible but has only been demonstrated at this resolution/extent.
Describe time scale and resolution constraints Daily timestep, tested over multi-decadal (1980–2024) simulations; supports dynamic re-discretisation at user-defined intervals to reflect land-use/management change.
Describe any numerical limitations and issues Currently compiles/runs on Linux only. The GMD 2026 paper notes equifinality risk from the relatively large parameter set (multiple switchable conceptualisations across hydrology, isotopes, and nitrogen), which the authors suggest addressing via sensitivity analysis or limits-of-acceptability calibration (e.g., DREAM(LoAX)).


Describe available calibration data sets
Upload calibration data sets if available:
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?
Is there a manual available? No
Upload manual if available:
Model website if any
Model forum / discussion board
Comments


This part will be filled out by CSDMS staff

OpenMI compliant No not possible
BMI compliant No not possible
WMT component No not possible
PyMT component No not possible
Is this a data component No
DOI model 10.5281/zenodo.16747634
For model version 1.0
Year version submitted 2025
Link to file https://doi.org/10.5281/zenodo.16747633
Can be coupled with:
Model info
Authors
Songjun Wu
Tetzlaff
Source code
DOI

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Introduction

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References




Featured reference(s) Open Access Status Year Type of Reference Cited
Wu, Songjun; Tetzlaff, Doerthe; Zheng, Yi; Soulsby, Chris; 2026. EcoTWIN 1.0: a fully distributed tracer-aided ecohydrological model tracking water, isotopes, and nutrients. Geoscientific Model Development, 192257–2278. 10.5194/gmd-19-2257-2026
cc-by · publishedVersion		 2026 a module overview describing a module 1


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