Spatial variation of water supply and demand in Sri Lanka

Water supplyWater demandRiver basinsRunoffIrrigation efficiency

Strategic Analyses of the National River Linking Project (NRLP) of India, Series 4. Water productivity improvements in Indian agriculture: potentials, constraints and prospects

Water productivityWater use efficiencyMultiple useIrrigation practicesIrrigation systemsWater qualityWater allocationCerealsCrop yieldLivestockMilk productionEconomic aspects

Policy interfacing and irrigation development in Tamil Nadu

AgroclimatologyGroundwater irrigationWellsTank irrigationCanalsIrrigation systemsPolicyIrrigated landWater use efficiency

Benefits of irrigation water transfers in the National River Linking Project: a case study of Godavari (Polavaram)-Krishna link in Andhra Pradesh

River basin managementDevelopment projectsWater scarcityWater transferGroundwater irrigationSurface irrigationLand useDamsRiceLivestock

Modernization using the structured system design of the Bhadra Reservoir Project, India: an intervention analysis

Performance evaluationIrrigation programsModernizationParticipatory managementFarmer participationFarmer-agency interactionsFarmers' attitudesRemote sensingRiceIrrigated farmingWater distributionWater supplyProductivity

Meeting India’s future water needs: policy options

River basinsWater shortageWater transferGroundwater irrigationWater productivity

Are there any ‘hot’ spots and ‘bright’ spots of rice water productivity in Bangladesh? A spatio-temporal analysis of district-level data

Employing Bangladeshi district-level time series data as an empirical exploration this paper aims to: (1) estimate two measures of rice water productivity for the main crop seasons; (2) undertake a spatio-temporal analysis; and (3) identify ‘hot’ spots and ‘bright’ spots focusing on the Ganges-dependent (GDA) vis-à-vis other districts (NGDA). The paper finds that (1) kharif (wet) season rice water productivity grew much faster than for the rabi (dry) season across all districts. There was no significant correlation between seasonal growth rates although significant correlation existed between seasonal growth rates and the annual growth rate. Eight Ganges dependent districts experienced faster growth rate in kharif and overall productivity but their rabi season performance was slower relative to other districts. (2) Marginal productivity (MP) experienced fastest growth for the kharif season during 1968-1980. Up to 1990, there was no significant growth in rabi MP. Its growth declined in the 1980s but picked up since the early 1990s. (3) MPs products were slightly lower in the GDA districts for kharif and overall. The study did not find any consistent ‘hot’ spots or ‘bright’ spots in Bangladeshi rice water productivity. The process is highly groundwater intensive and is debatable whether it is sustainable.

Impact assessment of rehabilitation intervention in the Gal Oya Left Bank [Sri Lanka].

Irrigation managementWater managementIrrigation systemsProductivityRehabilitationModelsProject evaluationRainReservoir storage

India’s water supply and demand from 2025-2050: business-as-usual scenario and issues

Water demandEstimationIrrigation waterRiver basinsWater supplySimulation modelsPopulation growthFood productionFood consumptionCrop yieldGroundwater irrigation

Resonance mode power supplies with power factor correction

There is an increasing need for AC-DC converters to draw a pure sinusoidal current at near unity power factor from the AC mains. Most conventional power factor correcting systems employ PWM techniques to overcome the poor power factor being presented to the mains. However, the need for smaller and lighter power processing equipment has motivated the use of higher internal conversion frequencies in the past. In this context, resonant converters are becoming a viable alternative to the conventional PWM controlled power supplies. The thesis presents the implementation of active power factor correction in power supplies, using resonance mode techniques. It reviews the PWM power factor correction circuit topologies previously used. The possibility of converting these PWM topologies to resonant mode versions is discussed with a critical assessment as to the suitability of the semiconductor switching devices available today for deployment in these resonant mode supplies. The thesis also provides an overview of the methods used to model active semiconductor devices. The computer modelling is done using the PSpice microcomputer simulation program. The modifications that are needed to the built in MOSFET model in PSpice, when modeling high frequency circuits is discussed. A new two transistor model which replicates the action of a OTO thyristor is also presented. The new model enables the designer to estimate the device parameters with ease by adopting a short calculation and graphical design procedure, based on the manufacturer's data sheets. The need for a converter with a high efficiency, larger power/weight ratio, high input power factor with reduced line current distortion and reduced cost has led to the development of a new resonant mode converter topology, for power processing. The converter presents a near resistive load to the mains thus ensuring a high input power factor, while providing a stabilised de voltage at the output with a small lOOHz ripple. The supply is therefore ideal for preregulation applications. A description of the modes of operation and the analysis of the power circuit are included in the thesis. The possibility of using the converter for low output voltage applications is also discussed. The design of a 300W, 80kHz prototype model of this circuit is presented in the thesis. The design of the isolation transformer and other magnetic components are described in detail. The selection of circuit components and the design and implementation of the variable frequency control loop are also discussed. An evaluation of the experimental and computer simulated results obtained from the prototype model are included in the presentation. The thesis further presents a zero-current switching quasi-resonant flyback circuit topology with power factor correction. The reasons for using this topology for off-line power conversion applications are discussed. The use of a cascoded combination of a bipolar power transistor and two power MOSFETs i~ the configuration has enabled the circuit to process moderate levels of power while simultaneously switching at high frequencies. This fulfils the fundamental precondition for miniaturisation. It also provides a well regulated DC output voltage with a very small ripple while maintaining a high input power factor. The circuit is therefore ideal for use in mobile applications. A preliminary design of the above circuit, its analysis using PSpice, the design of the control circuit, current limiting and overcurrent protection circuitry and the implementation of closed-loop control are all included in the thesis. The experimental results obtained from a bread board model is also presented with an evaluation of the circuit performance. The power factor correction circuit is finally installed in this supply and the overall converter performance is assessed