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Not AvailableIn large canal irrigation project areas, integrated management of surface and groundwater resources can improve water use efficiencies and agricultural productivity and also control water logging. Such integrated management requires an estimation of spatial distribution of recharge and ground water flow in the underlying aquifer. Recharge occurs both as percolation losses from fields and seepage losses from the water distribution network. Percolation losses are influenced by weather, soil properties, land use, and canal water and groundwater use. Seepage losses depend on the conditions of flow in the water distribution system. In large irrigation project areas all the factors influencing the recharge of groundwater vary spatially. In this study, a geographical information systems (GIS) is used to map the spatial distribution of recharge which then serves as input to a regional groundwater flow model for simulating the behavior of the underlying aquifer. The basis is that the project area can be divided into a set of basic simulation units (BSUs) that are homogenous with respect to the conditions that influence the recharge processes. A daily field soil water balance model and a simple canal flow model are used to estimate the percolation and seepage losses, respectively. The combination of models and GIS can be used as an integrated decision support system to assess the groundwater resources and derive strategies for integrated management of canal and groundwater resources in the project area. (C) 2003 Elsevier B.V. All rights reserved.Not Availabl

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Not AvailableAgriculture is the main non-point polluter of groundwater in irrigated areas as fertilizers and other agrochemicals are the main contaminants in the water that drains out of the root zone to recharge the aquifer. Nitrates from fertilizers, dissolved in percolation losses from rice fields, are the source of pollution considered. The concentration of nitrates in the percolated water depends on the distributed field water and nitrogen balances over the area. Its concentration in the groundwater depends on the total recharge, pollution loading, groundwater flow and solute transport within the aquifer. The development and application of a GIS based decision support framework that integrates field scale models of these processes for assessment of non-point-source pollution of groundwater in canal irrigation project areas is presented. The GIS is used for representing the spatial variations in input data over the area and map the output of the recharge and nitrogen balance models. The latter are used to provide the spatially distributed recharge and pollutant load inputs to the distributed groundwater flow and transport models, respectively. Alternate strategies for water and fertilizer use can be evaluated using this framework to ensure long-term sustainability of productive agriculture in large irrigation projects. The development and application of the framework is illustrated by taking a case study of a large canal irrigation system in India. (c) 2005 Elsevier B.V. All rights reserved.Not Availabl

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Not AvailableQuantification of nitrate losses is important for devising measures to ensure sustainability of soil fertility and groundwater resources and for the development of crop nutrient management protocols. Hence, in the present study a simple model for assessing concentration of nitrate in water percolating out of the flooded rice (Oryza Sativa) fields is presented. The model considers all the important nitrogen (N) transformation processes that take place in flooded rice fields such as urea hydrolysis, volatilization, nitrification, mineralization, immobilization, denitrification, crop uptake and leaching. It is based on coupling of soil water and N-balance models. The coupled model also accounts for weather, and timings and amounts of water and fertilizer applications. All the N-transformations except plant uptake and leaching are considered to follow first-order kinetics. A heuristic procedure is developed for selection of the rate constants of the transformation processes for different soil and environmental conditions. The model is evaluated by comparing simulation results with published data of three field experiments conducted at two locations namely G.B. Pant University Farm, Pantnagar, UP and IARI Research Farm, New Delhi of India, respectively. The simulation results show that urea hydrolysis is completed within 7 days of fertilizer application. It was also observed that the volatilization loss of N varies from 25 to 33% of the applied fertilizer and 75% of the total volatilization loss occurs within 7 days of urea application. The modeled leaching losses from the field experiments varied from 20 to 30% of the applied N. The N-uptake by the crop increased immediately after the application of fertilizer and decreased at 60 days after transplanting. The model is sufficiently general to be used in a wide range of conditions for quantification of nutrient losses by leaching and developing water and fertilizer management strategies for rice in irrigated areas. (C) 2004 Elsevier B.V. All rights reserved.Not Availabl