Showing papers by "K. P. Sudheer published in 2018"

Parameter estimation of SWAT and quantification of consequent confidence bands of model simulations

Abstract: Soil and Water Assessment Tool (SWAT) is a river basin scale model widely used to study the impact of land management practices in large, complex watersheds. Even though model output uncertainties are generally recognized to affect watershed management decisions, those uncertainties are largely ignored in model applications. The uncertainties of SWAT simulations are quantified using various methods, but simultaneous attempt to calibrate a model so as to reduce the uncertainty are seldom done. This study aims to use an uncertainty reduction procedure that helps calibrate the SWAT model. The shuffled complex evolutionary metropolis algorithm for uncertainty analysis is employed for this purpose, and is demonstrated using the data from the St. Joseph River basin, USA. The values of the performance indices, the r2 and the Nash–Sutcliffe efficiency (NSE) for the simulations during calibration period was found to be 0.81 (same for r2 and NSE) and 0.79 for validation period indicating a good simulation by the model. The results also indicate that the algorithm helps reduce the uncertainty (percentage of coverage = 62% and average width = 19.2 m3/s), and also identifies the plausible range of parameters that simulate the processes with less uncertainty. The confidence bands of simulations are obtained that can be employed in making uncertainty-based decisions on watershed management practices.

An improved representation of vegetative filter strips in swat

Abstract: Vegetative filter strips (VFS) are popular conservation practices installed at the edges of agricultural fields to reduce losses of pollutants from agricultural areas to receiving waterbodies. The recent interest in using VFS areas as multifunctional landscapes necessitates an improved depiction of VFS in simulation models. This study is aimed to enhance the physical representation of VFS in the Soil and Water Assessment Tool (SWAT) to improve the representation of ecohydrologic processes and land management practices in VFS areas. The proposed enhancement enables routing of water, sediment, and nutrients from the source area through the VFS area and makes the infiltrated water and nutrients available for filter crop uptake. The improvements are implemented in SWAT by modifying input files through Matlab scripts and by changing SWAT subroutines to enable routing. The model improvements are tested with three paired watershed studies with and without edge-of-field VFS in central Iowa. The improved model estimated 46% runoff reduction, 91% sediment reduction, 83% total phosphorus reduction, and 54% nitrate reduction with VFS, and these estimates closely matched the measured VFS reductions. The improved model was able to represent increased infiltration, soil moisture, and denitrification in the VFS area, along with accurately capturing crop yields in the source and VFS areas. Overall, the results indicate improved physical representation of VFS in SWAT.

Probabilistic and ensemble simulation approaches for input uncertainty quantification of artificial neural network hydrological models

Abstract: Artificial neural network (ANN) has been demonstrated to be a promising modelling tool for the improved prediction/forecasting of hydrological variables. However, the quantification of uncertainty ...

A computationally efficient method for uncertainty analysis of SWAT model simulations

Abstract: The physically based distributed hydrological models are ideal for hydrological simulations; however most of such models do not use the basic equations pertaining to mass, energy and momentum conservation, to represent the physics of the process. This is plausibly due to the lack of complete understanding of the hydrological process. The soil and water assessment tool (SWAT) is one such widely accepted semi-distributed, conceptual hydrological model used for water resources planning. However, the over-parameterization, difficulty in its calibration process and the uncertainty associated with predictions make its applications skeptical. This study considers assessing the predictive uncertainty associated with distributed hydrological models. The existing methods for uncertainty estimation demand high computational time and therefore make them challenging to apply on complex hydrological models. The proposed approach employs the concepts of generalized likelihood uncertainty estimation (GLUE) in an iterative procedure by starting with an assumed prior probability distribution of parameters, and by using mutual information (MI) index for sampling the behavioral parameter set. The distributions are conditioned on the observed information through successive cycles of simulations. During each cycle of simulation, MI is used in conjunction with Markov Chain Monte Carlo procedure to sample the parameter sets so as to increase the number of behavioral sets, which in turn helps reduce the number of cycles/simulations for the analysis. The method is demonstrated through a case study of SWAT model in Illinois River basin in the USA. A comparison of the proposed method with GLUE indicates that the computational requirement of uncertainty analysis is considerably reduced in the proposed approach. It is also noted that the model prediction band, derived using the proposed method, is more effective compared to that derived using the other methods considered in this study.

Effect of pre-treatments on quality parameters of vacuum fried ripened banana (Nendran) chips

Abstract: India is the major producer of banana in the world. Ripened banana chips is the favourite snack of the consumers of all age groups. In the present study, attempts were made to improve the quality and reduce the residual oil content of vacuum fried ripened banana chips through pre-treatments viz., blanching cum drying, gum coating, and freezing. The quality attributes like oil absorption, moisture content, water activity, texture, colour and sensory values were determined for all the products treated at frying temperature, pressure and time of 100o C, 20 k Pa and 10 min, respectively. The blanching cum drying pre-treatment showed significant (p<0.0001) oil reduction but exhibited poor consumer acceptability. However the freezing pre-treatment scored high consumer acceptability with high oil content of 38.2%. The gum coating pretreatment was on par with untreated vacuum fried chips. Untreated vacuum fried chips with post centrifugation at 1000 rpm for 5 min had low residual oil content of 13.4% and good consumer acceptability. Analysis revealed that untreated products were superior not only in terms of quality but also in terms of reduced cost and time for the protocol.

Development of fortified banana pseudostem juice powder utilizing spray drying technology

Abstract: Spray drying technology was optimized for the preparation of milk fortified banana pseudostem juice powder, overcoming the problems of browning and astringent taste. The taste and nutritional value of the powder was increased by blending it with milk, horse gram extract and cardamom powder. Spray drying parameters like inlet air temperatures of 185, 190 and 200° C, constant blower speed and feed speed of 1800 and 15 rpm were selected for the development of milk fortified banana pseudostem juice powder. Functional properties of final powder were analysed for assessing the quality characteristics. Moisture content, water activity, bulk density, colour characteristics and solubility of the powder were assessed by standard procedures. The treatment with 30% horse gram extract, 50% milk and 20% pseudostem juice exhibited appreciable quality enhancement during product analysis. During sensory analysis, the above treatment scored the best. Mineral profile analysis of standardised sample also revealed nutritive value of the trial product.