Papers by Narayanan Kannan

Scientific Reports
Vapor drift of applied pesticides is an increasing concern. Among the major crops cultivated in t... more Vapor drift of applied pesticides is an increasing concern. Among the major crops cultivated in the Lower Mississippi Delta (LMD), cotton receives most of the pesticides. An investigation was carried out to determine the likely changes in pesticide vapor drift (PVD) as a result of climate change that occurred during the cotton growing season in LMD. This will help to better understand the consequences and prepare for the future climate. Pesticide vapor drift is a two-step process: (a) volatilization of the applied pesticide to vapors and (b) mixing of the vapors with the atmosphere and their transport in the downwind direction. This study dealt with the volatilization part alone. Daily values of maximum and minimum air temperature, averages of relative humidity, wind speed, wet bulb depression and vapor pressure deficit for 56Â years from 1959 to 2014 were used for the trend analysis. Wet bulb depression (WBD), indicative of evaporation potential, and vapor pressure deficit (VPD), in...

Texas Water Journal
In recognition of the unique hydrologic functions they serve, certain stream segments in Texas ha... more In recognition of the unique hydrologic functions they serve, certain stream segments in Texas have been designated as ecologically significant. In this study, we evaluated low flow trends in seven hydrologically unique stream segments spanning three climatic divisions in Texas from 1970 to 2019. Despite increasing mean annual temperatures, there are no trends in low flows or other hydrologic variables in the East Fork of the San Jacinto River in the Upper Coast climatic division, likely due to local moisture surplus effects from the Gulf of Mexico. In the Edwards Plateau climatic division, annual low flows and annual baseflows are decreasing in the South Fork of the Guadalupe River, the Sabinal River and the Frio River. While increasing mean annual temperatures appear to have a role in the drying of all three of these stream segments, increasing annual potential evapotranspiration may be an additional driver in the Sabinal and Frio Rivers. Analysis of the Standardized Streamflow In...

Hydrology, 2021
Overall health of a stream is one of the powerful indicators for planning mitigation strategies. ... more Overall health of a stream is one of the powerful indicators for planning mitigation strategies. Currently, available methods to estimate stream health do not look at all the different components of stream health. Based on the statistical parameters obtained from daily streamflow data, water quality data, and index of biotic integrity (IBI), this study evaluated the impacts on all the elements of stream health, such as aquatic species, riparian vegetation, benthic macro-invertebrates, and channel degradation for the Plum Creek watershed in Texas, USA. The method involved the (1) collection of flow data at the watershed outlet; (2) identification of hydrologic change in the streamflow; (3) estimation of hydrologic indicators using NATional Hydrologic Assessment Tool (NATHAT) before alteration and after alteration periods; (4) identification of the most relevant indicators affecting stream health in the watershed based on stream type; (5) preliminary estimation of the existence of str...
International Journal of Research in Engineering and Technology, 2014

International Journal of Research in Engineering and Technology, 2014
Urban watersheds produce an instantaneous response to rainfall. That results in stormwater runoff... more Urban watersheds produce an instantaneous response to rainfall. That results in stormwater runoff in excess of the capacity of drainage systems. The excess stormwater must be managed to prevent flooding and erosion of streams. Management can be achieved with the help of structural stormwater Best Management Practices (BMPs). Detention ponds is one such BMP commonly found in the Austin, TX, USA. The City of Austin developed a plan to mitigate future events of flooding and erosion, resulting in the development and integration of stormwater BMP algorithms into the sub-hourly version of SWAT model. This paper deals with the development of a physically based algorithm for detention pond. The algorithm was tested using a previously flow-calibrated watershed in the Austin area. From the test results obtained it appears that the detention pond algorithm is functioning satisfactorily. The algorithm developed could be used a) to evaluate the functionality of individual detention pond b) to analyze the benefits of such structures at watershed or higher scales and c) as design tool.

Hydrology, 2018
Existing methods to estimate stream health are often location-specific, and do not address all of... more Existing methods to estimate stream health are often location-specific, and do not address all of the components of stream health. In addition, there are very few guidelines to estimate the health of a stream, although the literature and useful tools such as Indicators of Hydrologic Alteration (IHA) are available. This paper describes an approach developed for estimating stream health. The method involves the: (1) collection of flow data; (2) identification of hydrologic change; (3) estimation of some hydrologic indicators for pre-alteration and post-alteration periods; and (4) the use of those hydrologic indicators with the scoring framework of the Dundee Hydrologic Regime Assessment Method (DHRAM). The approach estimates the stream health in aggregate including all of the components, such as riparian vegetation, aquatic species, and benthic organisms. Using the approach, stream health can be estimated at two different levels: (1) the existence or absence of a stream health problem based on the concept of eco-deficit and eco-surplus using flow duration curves; and (2) the estimation of overall stream health using the IHA-DHRAM method. The procedure is demonstrated with a case example of the White Rock Creek watershed in Texas in the United States (US). The approach has great potential to estimate stream health and prescribe flow-based goals for the restoration of impaired streams.

Hydrology, 2019
This study is a part of the Conservation Effects Assessment Project (CEAP) aimed to quantify the ... more This study is a part of the Conservation Effects Assessment Project (CEAP) aimed to quantify the environmental and economic benefits of conservation practices implemented in the cultivated cropland throughout the United States. The Soil and Water Assessment Tool (SWAT) model under the Hydrologic United Modeling of the United States (HUMUS) framework was used in the study. An automated flow calibration procedure was developed and used to calibrate runoff for each 8-digit watershed (within 20% of calibration target) and the partitioning of runoff into surface and sub-surface flow components (within 10% of calibration target). Streamflow was validated at selected gauging stations along major rivers within the river basin with a target R2 of >0.6 and Nash and Sutcliffe Efficiency of >0.5. The study area covered the entire Mississippi and Atchafalaya River Basin (MARB). Based on the results obtained, our analysis pointed out multiple challenges to calibration such as: (1) availabil...
Integrating APEX Output for Cultivated Cropland with SWAT Simulation for Regional Modeling
Transactions of the ASABE, 2011

Journal of environmental quality, 2014
A modeling framework consisting of a farm-scale model, Agricultural Policy Environmental Extender... more A modeling framework consisting of a farm-scale model, Agricultural Policy Environmental Extender (APEX); a watershed-scale model, Soil and Water Assessment Tool (SWAT); and databases was used in the Conservation Effects Assessment Project to quantify the environmental benefits of conservation practices on cropland. APEX is used to simulate conservation practices on cultivated cropland and Conservation Reserve Program land to assess the edge-of-field water-quality benefits. Flow and pollutant loadings from APEX are input to SWAT. SWAT simulates the remaining noncultivated land and routes flow and loads generated from noncultivated land, point sources, and cropland to the basin outlet. SWAT is used for assessing the effects of practices on local and in-stream water-quality benefits. Each river basin is calibrated and validated for streamflow and loads at multiple gauging stations. The objectives of the current study are to estimate the effects of currently existing and additional con...

Urban watersheds produce an instantaneous response to rainfall. That results in stormwater runoff... more Urban watersheds produce an instantaneous response to rainfall. That results in stormwater runoff in excess of the capacity of drainage systems. The excess stormwater must be managed to prevent flooding and erosion of streams. Management can be achieved with the help of structural stormwater Best Management Practices (BMPs). Detention ponds is one such BMP commonly found in the Austin, TX, USA. The City of Austin developed a plan to mitigate future events of flooding and erosion, resulting in the development and integration of stormwater BMP algorithms into the sub-hourly version of SWAT model. This paper deals with the development of a physically based algorithm for detention pond. The algorithm was tested using a previously flow-calibrated watershed in the Austin area. From the test results obtained it appears that the detention pond algorithm is functioning satisfactorily. The algorithm developed could be used a) to evaluate the functionality of individual detention pond b) to analyze the benefits of such structures at watershed or higher scales and c) as design tool.

Transactions of the ASABE, 2012
SWAT (Soil and Water Assessment Tool) is a comprehensive, semi-distributed river basin model that... more SWAT (Soil and Water Assessment Tool) is a comprehensive, semi-distributed river basin model that requires a large number of input parameters, which complicates model parameterization and calibration. Several calibration techniques have been developed for SWAT, including manual calibration procedures and automated procedures using the shuffled complex evolution method and other common methods. In addition, SWAT-CUP was recently developed and provides a decision-making framework that incorporates a semi-automated approach (SUFI2) using both manual and automated calibration and incorporating sensitivity and uncertainty analysis. In SWAT-CUP, users can manually adjust parameters and ranges iteratively between autocalibration runs. Parameter sensitivity analysis helps focus the calibration and uncertainty analysis and is used to provide statistics for goodness-of-fit. The user interaction or manual component of the SWAT-CUP calibration forces the user to obtain a better understanding of the overall hydrologic processes (e.g., baseflow ratios, ET, sediment sources and sinks, crop yields, and nutrient balances) and of parameter sensitivity. It is important for future calibration developments to spatially account for hydrologic processes; improve model run time efficiency; include the impact of uncertainty in the conceptual model, model parameters, and measured variables used in calibration; and assist users in checking for model errors. When calibrating a physically based model like SWAT, it is important to remember that all model input parameters must be kept within a realistic uncertainty range and that no automatic procedure can substitute for actual physical knowledge of the watershed.
An Approach for Estimating Water Quality Benefits of Conservation Practices at the National Level
2005 Tampa, FL July 17-20, 2005, 2005
Development and Integration of Sub-hourly Rainfall–Runoff Modeling Capability Within a Watershed Model
Water Resources Management, 2010

JAWRA Journal of the American Water Resources Association, 2008
Physically based regional scale hydrologic modeling is gaining importance for planning and manage... more Physically based regional scale hydrologic modeling is gaining importance for planning and management of water resources. Calibration and validation of such regional scale model is necessary before applying it for scenario assessment. However, in most regional scale hydrologic modeling, flow validation is performed at the river basin outlet without accounting for spatial variations in hydrological parameters within the subunits. In this study, we calibrated the model to capture the spatial variations in runoff at subwatershed level to assure local water balance, and validated the streamflow at key gaging stations along the river to assure temporal variability. Ohio and Arkansas-White-Red River Basins of the United States were modeled using Soil and Water Assessment Tool (SWAT) for the period from 1961 to 1990. R 2 values of average annual runoff at subwatersheds were 0.78 and 0.99 for the Ohio and Arkansas Basins. Observed and simulated annual and monthly streamflow from 1961 to 1990 is used for temporal validation at the gages. R 2 values estimated were greater than 0.6. In summary, spatially distributed calibration at subwatersheds and temporal validation at the stream gages accounted for the spatial and temporal hydrological patterns reasonably well in the two river basins. This study highlights the importance of spatially distributed calibration and validation in large river basins.
Journal of Soil and Water Conservation, 2014
Mike White and Jeffrey G. Arnold are agricultural engineers with USDA Agricultural Research Servi... more Mike White and Jeffrey G. Arnold are agricultural engineers with USDA Agricultural Research Service in Temple, Texas. Chinnasamy Santhi and Narayanan Kannan are associate research scientists with Texas A&M University in Temple, Texas. Daren Harmel is an agricultural engineer and acting research leader with USDA Agricultural Research Service in Temple, Texas. Lee Norfleet is a soil scientist with USDA Natural Resources Conservation Service in Temple, Texas. Peter Allen is a professor with Baylor University in Waco, Texas. Mauro DiLuzio is a research scientist with Texas A&M in Temple, Texas. Xiuying (Susan) Wang is a research assistant professor with Texas A&M in Temple, Texas. Elizabeth Haney is a senior research associate with Texas A&M in Temple, Texas.
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Papers by Narayanan Kannan