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United States Department of Agriculture

Agricultural Research Service


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RZWQM2 is an enhancement of the Root Zone Water Quality Model (RZWQM), created on users' requests. Main components of the model were extensively validated and improved, and several new components added. As a result, RZWQM2 is an advanced, but practical, whole-system model for studying crop production, and soil, water and air quality under current and changing climate conditions. It emphasizes the effects of major agricultural management practices on physical, chemical and biological processes related to plant growth and development, the movement of water, nutrients, and pesticides, and energy balance on the soil surface and crop canopy. Recent additions include rule base irrigation (soil water depletion and ET deficit) and irrigation water limitations, choice of energy balance model and alternative plant water stress algorithms, automated input parameter optimization (PEST/BEOPEST), non-linear uncertainty analysis, and running management scenarios with uncertainty.

The model requires daily or hourly weather data (maximum and minimum daily temperature, solar radiation, wind speed, relative humidity, and rainfall), soil texture, soil bulk density, soil hydraulic properties (if known), and recorded management practices. It runs on a daily time step with exception of water and chemical movement that is on a sub-hourly time step. RZWQM2 is a one-dimensional model with a pseudo 2-dimensional drainage flow and water table fluctuation.

RZWQM2 versions are delivered through the web, . It has been transferred to users through personal discussions, training sessions, and collaborative testing/applications; The original core science in the model is documented in a book, which can be purchased at

RZWQM2 has all the following features:

 1. State-of-the-science simulation of management effects on soil-plant systems;
 2. Simulation of tile drainage systems and water table fluctuation;
 3. Simulation of macropore/preferential flow in soils;
 4. Options to use a generic plant growth model, quick plant modules, and DSSAT CSM models;

 5. Capability of simulating surface energy balance (SHAW) and its effects on soil-plant


 7. Sediment loss due to water erosion added from the GLEAMS model;
 8. User friendly Windows Interface to facilitate input/output management;
 9. Built-in database for soil, plant, pesticides, and weather generator inputs;
10. Rule-based implementations of management practices;
11. On-line help, User Guide, and Publications on model parameterization and applications;

12. Automated Calibration and Non-Linear Uncertainty Analysis (PEST/BEOPEST);

13. Ability to obtain confidence intervals of simulation results due to uncertainty of model inputs (distributed inputs).

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Operating System: Windows XP and later.

Latest Version: 3.00.01: Release date: Oct 20 2015 4:03pm

For more information, download Microsoft Word document or Adobe PDF Overviews.

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Last Modified: 12/1/2015
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