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RICEWQ

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.

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 re-suspension from sediment. The model can simulate up to five chemicals/metabolites.

Obtaining the Model

The Tier 2 RICEWQ-EXAMS modeling platform for Windows can be downloaded from the model download page.

You can also download the RICEWQ Users Manual without downloading the model.

For other versions of the model, including advanced versions of the RICEWQ-EXAMS modeling platform, contact us.

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 inputs 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, and drift factor. Sediment properties include initial suspended-sediment concentration, settling velocity, re-suspension velocity, porosity of bed sediment, and bulk density of bed sediment. Weather inputs include daily precipitation and daily or monthly pan evaporation.

Output Parameters

The hydrologic output file contains daily time series of precipitation, evaporation, seepage, irrigation, depth in paddy, and outflow from paddy. The pesticide output file contains daily time-series accounting for pesticide mass: outflow, degradation in water, volatilization, settled, re-suspended, diffused between water and sediment, degraded in sediment, and lost from active sediment layer due to burial.

References

Williams, W.M., A.M. Ritter, C.E. Zdinak, and J.M. Cheplick, 2008. RICEWQ: Pesticide Runoff Model For Rice Crops, Users Manual And Program Documentation, Version 1.7.3, Waterborne Environmental, Inc., Leesburg, VA, 2008.