1. General Model Information

Name: Pesticide Runoff Model for Rice Crops

Acronym: RICEWQ


Main medium: terrestrial+aquatic
Main subject: ecotoxicology, biogeochemistry, agriculture
Organization level: agro-ecosystem
Type of model: not specified
Main application:
Keywords: pesticide transport, rice production system, flooding conditions, water and pesticide mass balance

Contact:

W. Martin Williams and J. Mark Cheplick


Waterborne Environmental, Inc.
897-B Harrison Street, S.E.
Leesburg, VA 20175
Phone: (703) 777-0005
Fax: (703) 777-0767


Phone: (703) 777-0005
Fax: (703) 777-0767
email: wei@waterborne-env.com
Homepage: http://www.waterborne-env.com/modeling/index.html

Author(s):

W. Martin Williams, Amy M. Ritter, and J. Mark Cheplick

Abstract:

Purpose:
Rice production presents a unique problem with respect to agrochemical runoff because of the high seasonal rainfall, water management, and proximity of cropland to surface water bodies. Existing pesticide transport models are not configured to simulate the flooding conditions, overflow, and controlled releases of water that are typical under rice production.
RICEWQ was developed to simulate water and chemical mass balance associated with these unique governing processes.

Processes Simulated:
RICEWQ simulates pesticide transport from rice paddies based on water and pesticide mass balance. Water mass balance takes into account precipitation, evaporation, seepage, overflow, irrigation, and drainage. Pesticide mass balance can accommodate dilution, advection, volatilization, partitioning between water/sediment, decay in water and sediment, burial in sediment, and resuspension from sediment.
The water quality algorithms first originated from the SWRRBWQ Lake Water Quality Model (LAKEWQ) developed by Jeff Arnold and Nancy Sammons, USDA-ARS, Temple, TX. Agronomic and hydrologic routines have been added to represent rice culture. Water quality algorithms have been modified for error checking and to allow first-order degradation. Nutrient algorithms from SWRRBWQ have not been included. To the extent possible and convenient, variable names and coding have remained unaltered from LAKEWQ. RICEWQ uses a daily time step.

Input Parameters:
Pesticide properties include the number of pesticide applications, dates of application, rate of application, washoff coefficient, water/sediment partition coefficient, degradation rate in water, degradation rate in sediment, mixing velocity (diffusion), and rate of volatilization.
Other key input include beginning and ending date of simulation, surface area of paddy, initial depth of water in paddy, depth of paddy outlet, seepage rate of paddy, depth to initiate and terminate irrigation, date that paddy is drained, crop emergence and maturation dates, drift factor.
Sediment properties include initial suspended sediment concentration, settling velocity, resuspension velocity, porosity of bed sediment, and bulk density of bed sediment.
Weather input include daily precipitation and daily or monthly pan evaporation.

Output Parameters:
Hydrologic output file contains daily time series of precipitation, evaporation, seepage, irrigation, depth in paddy, and outflow from paddy. Pesticide output file contains daily time series accounting of pesticide mass: applied, outflow, degradation in water, volatilization, settled, resuspended, diffused between water and sediment, degraded in sediment, and lost from active sediment layer due to burial.

Current Version No.: 1.2

Critical Assessment:
Strengths of Model: RICEWQ simulates the flooding conditions and water management typical for rice production. The model is extremely easy to use and was intentionally designed to not be overly sophisticated with algorithms for which input and validation data are seldom available.

Weaknesses of Model:
Degradation is represented by lumped 1st-order kinetics. Distinct biological and chemical transformation processes are not included as a standard option, but have been included for one case study. Degradation products are currently not simulated.

Source of abstract: American Crop Protection Association (ACPA) model database (04/1998)


II. Technical Information

II.1 Executables:

Operating System(s): Modest - IBM compatible 80286, IBM DOS Pre-processors: For bulk file processing.
Post-processors: For bulk file processing, automated graphics macros under Quattro Pro.


II.2 Source-code:

Programming Language(s): Source Code is available under copyright agreement.

II.3 Manuals:



II.4 Data:



III. Mathematical Information


III.1 Mathematics


III.2 Quantities




III.2.1 Input


Input Parameters:
Pesticide properties include the number of pesticide applications, dates of application, rate of application, washoff coefficient, water/sediment partition coefficient, degradation rate in water, degradation rate in sediment, mixing velocity (diffusion), and rate of volatilization.

Other key input include beginning and ending date of simulation, surface area of paddy, initial depth of water in paddy, depth of paddy outlet, seepage rate of paddy, depth to initiate and terminate irrigation, date that paddy is drained, crop emergence and maturation dates, drift factor.

Sediment properties include initial suspended sediment concentration, settling velocity, resuspension velocity, porosity of bed sediment, and bulk density of bed sediment.

Weather input include daily precipitation and daily or monthly pan evaporation.


III.2.2 Output


Output Parameters:
Hydrologic output file contains daily time series of precipitation, evaporation, seepage, irrigation, depth in paddy, and outflow from paddy. Pesticide output file contains daily time series accounting of pesticide mass: applied, outflow, degradation in water, volatilization, settled, resuspended, diffused between water and sediment, degraded in sediment, and lost from active sediment layer due to burial.

Output Flexibility:
Time series output file is easily modified for linkage to most receiving water models.


IV. References




V. Further information in the World-Wide-Web


VI. Additional remarks

RICEWQ has been validated on 8 rice paddies throughout Arkansas and Luisiana.
Publications pending permission from the study sponsors.


Last review of this document by: Juergen Bierwirth Tue Mar 17 11:03:10 MET 1998
Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:48 CEST 2002

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