Example of Case Studies

Synthetic Test Cases

A total of 10 synthetic test cases have been developed to verify OpenWQ’s outputs against analytical solutions. These tests cover batch reactors with different reaction orders and advection-dispersion transport scenarios. See Synthetic tests for the full list.

The JSON input files for each synthetic test can be obtained from: https://github.com/ue-hydro/synthetic_tests

PHREEQC River Geochemistry

A test case demonstrating PHREEQC geochemical modeling coupled with mizuRoute river routing is available in the test_case_phreeqc/ directory of the mizuRoute-OpenWQ repository.

This example simulates the transport and geochemical evolution of Ca, Mg, and Na through a river network, including:

  • Equilibrium speciation of dissolved species

  • Advective transport between river reaches

  • Temperature-dependent reaction calculations

  • HDF5 output of species concentrations

Configuration files include:

  • openWQ_master.json – Master configuration with Forward Euler solver

  • openwq_in/openWQ_config.json – Initial conditions (Ca, Mg, Na in mol/kgw)

  • openwq_in/openWQ_MODULE_PHREEQC.json – PHREEQC module settings

  • openwq_in/openWQ_MODULE_TD.json – Pure advection transport

  • openwq_in/phreeqc_river.pqi – PHREEQC input file

  • openwq_in/phreeqc.dat – Thermodynamic database

Nutrient Cycling (BGC-Flex)

OpenWQ’s flexible reaction network approach is well suited for nutrient cycling simulations. Using the BGC-Flex module, users can define nitrogen and phosphorus cycle reactions with temperature-dependent kinetics.

Example applications include:

  • Nitrogen cycle: Nitrification, denitrification, mineralization, and plant uptake with temperature and moisture dependencies

  • Phosphorus cycle: Sorption-desorption, mineralization, and particulate transport

  • Dissolved oxygen: BOD decay, reaeration, and sediment oxygen demand

These reaction networks are defined entirely in JSON configuration files. See Modules for the file format and the Theoretical Foundation for the underlying equations.