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Simulating seasonal variability of phytoplankton in stream water using the modified SWAT model
Pyo, JongCheol,Pachepsky, Yakov A.,Kim, Minjeong,Baek, Sang-Soo,Lee, Hyuk,Cha, YoonKyung,Park, Yongeun,Cho, Kyung Hwa Elsevier 2019 Environmental modelling & software Vol.122 No.-
<P><B>Abstract</B></P> <P>The ability to simulate algal systems is critical for watershed-scale models. The objective of this study was to develop and evaluate a modified algal module that simulates the dynamics of three major algal groups (cyanobacteria, green algae, and diatoms) in a stream using variables available in the Soil and Water Assessment Tool. The proposed module 1) models the dynamics of the three algal groups while accounting for nutrients from algal die-off and 2) has temperature multipliers that consider the effect of temperature changes on kinetic rates. Data to test the module were collected from a forest-dominated watershed over two years. The modified module was efficient in predicting seasonal variations in algal group biomass and simulated the regeneration of nutrients after algal die-off. This module will be useful in predicting the dynamics of the three studied algal groups and evaluating the best management practices for algal blooms in watersheds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The modified algal module was applied to the SWAT model. </LI> <LI> The algae-specific temperature correction term was applied to the process rates. </LI> <LI> The regeneration of organic nutrients after algal die-off was reasonably introduced. </LI> <LI> The module successfully reproduced the seasonal variation in phytoplankton biomass. </LI> </UL> </P>
Modeling seasonal variability of fecal coliform in natural surface waters using the modified SWAT
Cho, K.H.,Pachepsky, Y.A.,Kim, M.,Pyo, J.,Park, M.H.,Kim, Y.M.,Kim, J.W.,Kim, J.H. North-Holland Pub. Co ; Elsevier 2016 Journal of hydrology Vol.535 No.-
Fecal coliforms are indicators of pathogens and thereby, understanding of their fate and transport in surface waters is important to protect drinking water sources and public health. We compiled fecal coliform observations from four different sites in the USA and Korea and found a seasonal variability with a significant connection to temperature levels. In all observations, fecal coliform concentrations were relatively higher in summer and lower during the winter season. This could be explained by the seasonal dominance of growth or die-off of bacteria in soil and in-stream. Existing hydrologic models, however, have limitations in simulating the seasonal variability of fecal coliform. Soil and in-stream bacterial modules of the Soil and Water Assessment Tool (SWAT) model are oversimplified in that they exclude simulations of alternating bacterial growth. This study develops a new bacteria subroutine for the SWAT in an attempt to improve its prediction accuracy. We introduced critical temperatures as a parameter to simulate the onset of bacterial growth/die-off and to reproduce the seasonal variability of bacteria. The module developed in this study will improve modeling for environmental management schemes.
APEX 모델을 이용한 유역 단위 박테리아 거동 모듈 개발
홍은미 ( Eun-mi Hong ),( Yakov. A. Pachepsky ) 한국농공학회 2018 한국농공학회 학술대회초록집 Vol.2018 No.-
Every year approximately 76 million people in the U.S. experience foodborne diseases. Pathogenic microorganisms in irrigation and recreational waters have remained the subject of concern. These pathogens originate primarily from animal waste and wastewater. Water quality models can be essential tools for alleviating pathogen load to water sources, evaluating microbial contamination-related risks, guiding the microbial water quality monitoring, and assessing the effect of agricultural management on the microbial water quality. The objective is to develop a process-based model for simulating the fate and transport of manure-borne bacteria on land and in streams with the Agricultural Policy/Environmental eXtender (APEX) which are watershed-scale water quality model that includes detailed representation of agricultural management. The total number of bacteria removed by runoff and bacteria survival in manure is simulated. Bacteria survival patterns is simulated individually for each manure application event. In-stream microbial fate and transport processes include bacteria release from streambeds by sediment resuspension during high flow events, diffusive releases from the streambed sediment during low flow periods, bacteria deposition by sediment settling, and survival. These newly developed models were applied to simulate fate and transport of the fecal indicator bacterium Escherichia coli in the Toenepi watershed, New Zealand. Results show that the APEX with the bacteria module reproduced well the monitored pattern of E. coli concentrations at the watershed outlet. These developed model could be used to guide the development of microbial water quality monitoring strategy.