Showing papers by "Narendra Singh Raghuwanshi published in 2002"

Estimating Evapotranspiration using Artificial Neural Network

Abstract: This study investigates the utility of artificial neural networks (ANNs) for estimation of daily grass reference crop evapotranspiration (ETo) and compares the performance of ANNs with the conventional method (Penman–Monteith) used to estimate ETo. Several issues associated with the use of ANNs are examined, including different learning methods, number of processing elements in the hidden layer(s), and the number of hidden layers. Three learning methods, namely, the standard back-propagation with learning rates of 0.2 and 0.8, and backpropagation with momentum were considered. The best ANN architecture for estimation of daily ETo was obtained for two different data sets (Sets 1 and 2) for Davis, Calif. Using data of Set 1, the networks were trained with daily climatic data (solar radiation, maximum and minimum temperature, maximum and minimum relative humidity, and wind speed) as input and the Penman–Monteith (PM) estimated ETo as output. The best ANN architecture was selected on the basis of weighted sta...

Decision Support System for Estimating Reference Evapotranspiration

Abstract: Evapotranspiration (ET) is a major component of the hydrologic cycle and its accurate estimation is essential for hydrological studies. In the past, various estimation methods have been developed f...

Alternative Delivery Scheduling for Improved Canal System Performance

Abstract: Alternative delivery scheduling approaches intended to overcome the problem of low efficiency in Indian irrigation projects are presented. The features of the historical delivery schedules in the Right Bank Main Canal system of Kangsabati irrigation project, located in the state of West Bengal, India, have been studied, and nine modified schedules of varied rate rotation (variable discharge, constant duration, and constant frequency) prepared. Daily water balance simulation of the command area in the Kharif (rainy) season has been used to compare the performance of alternate schedules. An alternate schedule with three irrigations of 20 to 21 days' duration, followed by 20 days of canal closure after each irrigation, was found to perform the best. The proposed alternate schedule results in a better match between supply and demand and results in 13% water saving when compared to the existing schedules. The irrigation periods of this schedule cover the expected dry spells and critical rice growth stage. An added advantage of the proposed schedule is an improvement in the reliability of supply, which will encourage farmers to invest more on other inputs resulting in enhanced water use efficiency and improved yields.

2-D Saturated-Unsaturated Zone Irrigation and Drainage Model: Part I. Theory

Abstract: An integrated saturated–unsaturated zone model coupling irrigation, evaporation, vadose zone, and groundwater processes is needed to understand interaction among various hydrological processes affecting irrigated agriculture and to solve irrigation–related drainage problems. The SWMS_2D model was modified to simulate heterogeneous evaporation and transpiration, heterogeneous crop–specific root water uptake and dynamic root growth, and a temporally and spatially varying surface/atmospheric boundary flux including surface ponding. This article presents the theory related to these model improvements. Evapotranspiration partitioning was incorporated to separate crop reference evapotranspiration into evaporation and transpiration using a ground shading approach that can accommodate the unique growth characteristics of particular crops. Dynamic crop–specific root water uptake and heterogeneous fluxes of water and solutes through the surface were developed as features of the model. An accompanying article considers the model sensitivity analysis.

2-D saturated-unsaturated zone irrigation and drainage model: Part II. Sensitivity analysis

Abstract: The modified SWMS_2D model described in the previous article was used to study sensitivity of model output to critical head, sorption distribution coefficient, initial solute concentration, distal boundaries, plant water uptake parameters, irrigation schedules, and soil type considering a 100 m U 9 m transect in the western San Joaquin Valley. Output was found insensitive to reductions in minimum soil water suction head (hd) and distal boundaries located 1000 m away from the domain of interest, and was found to be sensitive to values of sorption coefficient (Kd), plant water uptake parameters, irrigation schedules, and soil type. Finally, application of a method to separate evapotranspiration into evaporation and transpiration by deriving the ground shading parameters from crop coefficients was demonstrated. The results suggest that the modified SWMS_2D model can be used for irrigation and drainage management.