Simulation and Evaluation of Stream Flow and Pesticide Prediction in Orestimba Creek Watershed Using the AnnGNPS Model
Simulation and Evaluation of Stream Flow and Pesticide Prediction in Orestimba Creek Watershed Using the AnnGNPS Model

Author: Chen Wang

Publisher:

Published: 2014

Total Pages: 178

ISBN-13:

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Pesticides have been recognized as one major agricultural non-point source (NPS) pollution to the environment and surface water in United States. Numerous mathematical models have been developed over the last decades to simulate the fate and transport of NPS at watershed scale. Geographic Information System (GIS) combined with models extends the spatial and temporal scopes of the research by integrating a variety of climates, soils, land covers, and management practices. The Annualized Agricultural Nonpoint Source model (AnnAGNPS) has received considerable attention in the United States for estimating runoff, sediment yield, pesticide and nutrients transport from ungauged agricultural watershed. However, few studies have been conducted on pesticide loading prediction in surface water using AnnAGNPS. In this study, the AnnAGNPS model was calibrated and validated for prediction of stream flow and chlorpyrifos loading for an agricultural dominated watershed of Orestimba Creek, in Central Valley, California. Large amounts of chlorpyrifos are applied to almonds, walnuts and other stone-fruit orchards in this area every year, which caused significant concern regarding their contamination to the San Joaquin River. Variety of data obtained from multiple sources were utilized as model input, including climate, land use, topology, soil, crop management and schedule, non-crop data, and pesticide. The model's performance was quantitatively analyzed using mean, standard deviation, coefficient of determination (r 2), coefficient of efficiency (NSE), and root mean square error (RMSE). Model's prediction was considered to be unsatisfactory if NSE 0.36, satisfactory if 0.36

Assessing Pesticide Loading and Concentration with Assistance of Integrated Hydrological Models in Streams of Small to Medium-sized Watersheds
Assessing Pesticide Loading and Concentration with Assistance of Integrated Hydrological Models in Streams of Small to Medium-sized Watersheds

Author: Wei Chen

Publisher:

Published: 2020

Total Pages: 0

ISBN-13:

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Pesticides are increasingly used around the world alone with the expansion of intensive crop cultivation and food production. Pesticide residues from agriculture fields being carried to surface and ground water impose a potential threat to the aquatic ecosystem as well as to human health. However, monitoring potential threat of pesticide residuals in river systems is expensive and difficult. Previous studies indicated that traditionally used grab sampling methods could potentially underestimate the maximum concentrations of pesticide residues in streams by 10 to 1000 times. The objective of this study was to assess pesticide loading and concentration with assistance of integrated hydrological models in streams of small to medium-sized watersheds. Soil and Water Assessment Tool (SWAT) was selected for simulating hydrological processes together with pesticide loading and in stream pesticide concentration. Model predicted pesticide loading and pesticide concentration was compared with three years measured data from Black Brook Watershed and two Sub-basins within the same watershed. We found that the model predicted pesticide loading and in stream concentrations of three pesticides had the same seasonal trend with field surveys with some discrepancies. The discrepancies are likely caused by three main factors. 1. Model predicts the daily pesticide loading and daily average pesticide concentration and while actual pesticide concentrations change rapidly during stormflow period. 2. Current field sampling method could not capture the rapid change of pesticide concentration due to mechanical limitations. 3. Input data on exact pesticide application data were not available. In general, the pesticide modelling results indicate that the model is an effective tool in loading and concentration prediction in small agricultural watershed. We also found the model predicted pesticide loading during baseflow period were relatively high compare[d] with near zero pesticide concentration observed. This suggest[s] there is a need to improve in pesticide routing algorithm in SWAT model and current estimation during based flow period should be manually adjusted.

An Overview of the Hydrologic Simulation Program-FORTRAN, a Simulation Model for Chemical Transport and Aquatic Risk Assessment
An Overview of the Hydrologic Simulation Program-FORTRAN, a Simulation Model for Chemical Transport and Aquatic Risk Assessment

Author: TO. Barnwell

Publisher:

Published: 1982

Total Pages: 11

ISBN-13:

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This paper reviews the development of the Hydrologic Simulation Program-FORTRAN (HSPF), a comprehensive simulation model for predicting watershed hydrology, water quality, agricultural chemical migration, and risk assessment. The model uses such information as the time history of rainfall, temperature, and solar intensity, and characteristics of the land surface, such as land use patterns, soil characteristics, and agricultural practices, to simulate the processes that occur in a watershed. The flow rate, sediment load, and nutrient and pesticide concentrations are predicted. The model takes these results and information about the stream channels in the watershed and simulates the processes that occur in these streams. This part of the simulation produces a time history of water quantity, quality, and chemical transport at any point in a watershed--the inflow to a lake, for example. For ease of presentation and interpretation, flexible routines are provided for statistical analysis of the simulation output. A risk assessment methodology to evaluate lethal and sublethal effects, using the median lethal concentration (LC50) and maximum acceptable toxicant concentration (MATC) as the key effects parameters, is part of the analysis.