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PATRIOT |
A Methodology and Decision Support System for Evaluating the Leaching Potential of Pesticides
The EPA's Pesticide Assessment Tool for Rating Investigations of Transport (PATRIOT) is a methodology for providing rapid analyses of groundwater vulnerability to pesticides on a regional, state or local level. An appropriate measure of groundwater vulnerability is achieved by quantifying the leaching potential of a pesticide in terms of the mass transported to the top of the water table. The PATRIOT software package integrates, in a PC environment, a tool that enables scientifically-sound analysis of pesticide leaching potential with the data needed to use the tool for area-specific analyses anywhere in the conterminous United States. PATRIOT is comprised of (i) a chemical fate and transport model (PRZM-II), (ii) a comprehensive database, (iii) capabilities that allow you to explore the database and select the data appropriate to characterize local environmental factors and pesticide application scenarios, (iv) a directed sequence of interaction that guides you as you provide all the necessary information to perform alternative model analyses and (v) effective, user-selected, methods of summarizing and visualizing model results.
The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) has given a strong mandate to the States to develop pesticide management plans on both state and local levels. One of the most pressing concerns in pesticide management today, particularly in agricultural areas, is protecting our nation's groundwater supplies from invasion by pesticides. In order to make sound management decisions, there is a need to understand the potential for pesticides to leach from application sites through the underlying soils' unsaturated zone and into groundwater aquifers. Pesticide leaching is highly site-specific, and predicting the expected extent of leaching is not a simple task. The tendency to leach to groundwater is determined by the combined factors of climate, pesticide chemodynamics, soils properties, agricultural practices, and depth to groundwater. Accurate estimation of leaching potential requires analysis techniques that consider all of these factors.
The EPA Office of Technology Transfer and Regulatory Support (OTTRS) has initiated a research program to develop information systems for use in preventing or minimizing groundwater contamination by pesticides. The purpose of this program is to provide practical tools, with a strong scientific base, to the States in order to support the development of local pesticide management plans as mandated by FIFRA and implemented by the EPA Office of Pesticide Programs.
PATRIOT integrates existing technologies and hydrogeologic information into a framework for risk assessment and management of agricultural pesticides. The system enables state and local decision makers to rapidly analyze information about pesticides, soils and other relevant factors in order to make sound recommendations about pesticide use that will protect groundwater quality. Data investigations and model analyses can be evaluated within state, county, USDA Major Land Resource Area, or USGS Hydrologic Cataloging Unit boundaries.
The primary targeted users of PATRIOT are State personnel charged with developing local pesticide management plans. An additional user community will reside within EPA headquarters and Regional offices, where the tool will aid those involved in evaluating specific pesticides or pesticide management plans. While data analysis is not the primary function of the software package, it is likely that a broad base of environmental professionals may adopt PATRIOT as a convenient tool to explore the environmental data that support model analyses.
The PATRIOT software package provides comprehensive databases that satisfy the needs for rainfall, soils properties and occurrence, pesticide properties, and cropping practices. Pesticide-crop relationships and depth to water table estimates must be supplied by the PATRIOT user. The attributes of the PATRIOT database are as follows:
Rainfall. 10 years of daily rainfall values are included at 184 first-order NOAA weather stations distributed across the conterminous United States.
PATRIOT integrates a chemical fate and transport model of the unsaturated zone named PRZM-II (4) with supporting databases. The tasks of preparing input for model analyses and interpreting the model's results are supported by analysis and graphics capabilities that are peripheral to the core model and customized to allow efficient analysis of the specific problem that PATRIOT addresses (i.e., leaching potential to the water table).
The use of EPA Athen's PRZM-II model in PATRIOT enables the following general capabilities:
PATRIOT is designed specifically for minimal user input and rapid analysis in a PC environment; interaction with both the model and the databases has been implemented using the interface development tool AIDE (5). For PATRIOT, AIDE has been used to implement four major categories of user interaction: (i) on-line documentation and assistance, (ii) analysis of databases, (iii) development of model input and execution of the model, and (iv) selection of evaluation options for model output.
Comprehensive on-line documentation and assistance has been provided through the use of two tools: AIDE and Expert Help (6). AIDE features such as Limits (displays allowable values for user responses to data queries), and Status (displays system status in a window) provide a first level of assistance to PATRIOT users, and can be viewed directly on PATRIOT screens. Additional help for PATRIOT users has been developed using the documentation tool Expert Help. After viewing an initial, context-sensitive help message, Expert Help allows you to branch out in different directions in the documentation to pursue additional information on related topics.
Interaction with the databases has been enabled by implementing option menus related to attribute searching, ranking and statistical analysis, and by displaying the products that result from selecting the menu options (i.e., summary displays, graphics and mapping). In addition, to menu selections, two other modes of providing information are used: general data entry fields and "toggled" data fields that only allow selection of "on" or "off" conditions. AIDE has been used to develop a directed mode of database interaction dedicated to developing all the necessary input for a variety of user-selected PRZM-II analysis options. Finally, menus have been developed that enable the user to select various alternatives for compiling and viewing model results.
PATRIOT provides supportive graphics at every stage (data analysis, model input development, model results evaluation) of the process of pesticide leaching potential analysis.
The general graphics capabilities for PATRIOT are:
The graphics products of PATRIOT can all be printed on a printer or plotter, and are designed to provide much of information needed for individual hard copy reports on the leaching potential of specific pesticides within specific environmental scenarios.
The PATRIOT software is comprised of three branches of code: an ANALYSIS branch, an INPUT branch, and an ESTIMATE branch. A typical application of PATRIOT will require user interaction with all four databases: rainfall, soils properties, pesticide properties, and cropping practices. PATRIOT embodies a "stepping stone" approach to assessing pesticide leaching potential: The results of database search activities performed in the ANALYSIS branch are a prerequisite to specifying model input in the INPUT branch, and the input specification activities in the INPUT branch are prerequisites to performing any of the model analysis alternatives that are executed and summarized in the ESTIMATE branch.
Providing the input needed to perform model analyses requires iterative visits, first to the ANALYSIS branch and then to the INPUT branch, to interact with each of the four databases. The ANALYSIS branch enables the user to investigate each database and identify the appropriate data to fuel model analyses of area- and pesticide-specific scenarios. These data are stored in a buffer and identified in a "worksheet" to which the INPUT branch refers as a first step in the effort to establish the values for each data type that will be used to execute the model. Within the INPUT branch, two activities are performed. First, for model input that is supplied directly by the databases, the user is allowed to view, refine and assign to the model the data resident in the buffer after search activity was completed in the ANALYSIS branch. Second, the user is prompted to provide additional input, independent of the databases, that is used to establish model analysis options. A user enters the ESTIMATE branch only after all databases have been investigated, and all information necessary to perform a user-specified model analysis option has been established. If the user attempts to invoke an analysis by selecting an option in the ESTIMATE branch before all the necessary data have been provided, he/she will be returned to the INPUT branch, where an indicator of missing data/decisions is provided.
When dealing with each of the databases, the user performs iterative searches in the ANALYSIS branch, fine-tuning the search criteria until the contents of the buffer satisfy the desired scope of the model analysis (i.e., the proper number of data with the appropriate characteristics or geographic location).
When the user first enters the INPUT branch, he/she is prompted to define general run information (e.g., number of analysis scenarios, standard or Monte Carlo run) that are desired; when the basic run characteristics have been defined, the interface grooms its prompts to obtain all the information/decisions from the user and databases that are required to execute the specified analysis.
After all the databases have been explored in the ANALYSIS branch, and all information required for model execution has been specified in the INPUT branch, the user proceeds to the ESTIMATE branch to specify output products and invoke model execution. In a time span of minutes, the model computes leaching potential and produces output in the user-selected format. The user may then view the model results for up to 10 combinations of pesticide/soil/cropping practices/infiltration, evaluate the results and define new runs, or, when results are acceptable, save them in files or print hard copies.
