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Modelling Management Effects on Water Quality and Crop Production

Title: ROOT ZONE WATER QUALITY MODEL - Modelling Management Effects on Water Quality and Crop Production
Editors: L.R. Ahuja, K.W. Rojas, J.D. Hanson, M.J. Shaffer, L. Ma
Specifications: Soft Cover, 384 pp

ISBN-10: 1887201084
ISBN-13: 9781887201087

Price: US $95


RZWQM2 Version 4.2 is available to download at USDA ARS Software Site
Operating System: Windows 7 and later. Latest Version: 4.2: Release date: September 23, 2020 Software Information: RZWQM2 is an enhancement of the Root Zone Water Quality Model (RZWQM) . Main components of the model were extensively validated and improved, and several new components added. 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 surface energy balance. RZWQM2 is a one-dimensional model with a pseudo 2-dimensional drainage flow and water table fluctuation

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 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, DSSAT CSM 4.0 models, and HERMES SUCROS model;

5. Simulation of surface energy balance from the SHAW model;

7. Sediment loss due to water erosion added from the GLEAMS model;

8. User friendly Windows Interface to facilitate input/output data 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). 

Technical Support Contact:
Operating System: Windows 7 and later.
Latest Version: 4.2: Release date: September 23, 2020


The Root Zone Water Quality Model (RZWQM) is a comprehensive simulation model designed to predict the hydrologic response, including potential for surface and groundwater contamination, of alternative crop-management systems. It simulates crop development and the movement of water, nutrients and pesticides over and through the root zone for a representative unit area of an agricultural field over multiple years.

The model allows simulation of a wide spectrum of management practices and scenarios. These management alternatives include evaluation of: conservation tillage and residue cover versus conventional tillage; methods and timing of fertilizer and pesticide applications; manures and alternative chemical formulations; irrigation and drainage, and the methods and timing of water applications; and different crop rotations.

The model contains special features such as the rapid transport of surface-applied chemicals through macropores to deeper depths and the preferential transport of chemicals within the soil matrix via mobile-immobile zones. The transfer of surface-applied chemicals (pesticides in particular) to runoff water is also an important component.

To adequately evaluate the effect of certain long-term management practices on water quality and production, RZWQM can be run for up to 100 years using automated execution of certain management operations relative to crop growth stage in crop rotation, such as fertilizer application based on recommended formulas, irrigation scheduling, and harvesting. The unique features of the model are:

-> Agricultural management practices and their effects on crop production and environmental quality (tillage, irrigation, fertilization, manure application, tile drainage, pesticide application, and crop rotation).

-> Macropore/preferential flow.

-> Water table fluctuation.

-> Chemical transport in runoff/percolation water.

-> Detailed carbon/nitrogen dynamics with consideration of microbial populations.

-> Detailed plant physiological processes and plant population development.

-> Multiple year simulation with capability of answering 'what-if' scenarios.

-> With on-line help to guide model parameterization. ISBN 1-887-201-08-4. Publ. 2000 WRP.

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