Role of Sediment in the Design and Management of Irrigation Canals

ISBN-13: 9780415615792 / Angielski / Miękka / 2010 / 296 str.

Krishna P. Paudel

Opis

The performance of irrigation schemes that carry sediment laden water is often poor. Modern irrigation schemes are increasingly demand based, which means that the water flow in the canals is determined by the crop water requirements. Accordingly the flow in the canal network is not constant as the crop water requirement changes with the climate and the growing stages. Also the inflow of the sediment is not constant throughout the irrigation season. Such schemes, particularly having unlined canals in alluvial soils, are difficult to design and to manage without compromising the flexibility or maintenance cost. This research has made an in-depth assessment on the role of sediment in the design and management of an irrigation scheme by using the data of Sunsari Morang Irrigation Scheme, Nepal. An analysis of the velocity and shear stress distribution across a non-wide trapezoidal canal has been made to derive the correction factor for the sediment transport predictors.

Spis treści

1. Introduction1.1. General1.2. Prospects of irrigation1.3. Essentials of irrigation schemes1.3.1. Functional requirement1.3.2. Service requirement1.3.3. Operation and maintenance requirement1.4. Sediment transport aspects in irrigation canals1.4.1. Canal design1.4.2. Operation and management1.5. Irrigation in Nepal1.6. Mathematical modelling1.7. Objectives1.8. Set-up of the thesis 2. Irrigation in Nepal2.1. General overview2.2. Land and water resources2.3. History of irrigation development2.3.1. Ancient Period2.3.2. Medieval Period2.3.3. Modern Period2.4. Issues of the irrigation sector2.5. Description of the study area2.5.1. Location and development2.5.2. Major problems2.5.3. Modernization works3. Design of canals for sediment transport3.1. Background3.2. Design methods3.2.1. Regime theory3.2.2. Tractive force theory3.2.3. Rational theory3.3. Water flow hydraulics3.3.1. Governing equations3.3.2. Roughness prediction3.4. Sediment transport aspects3.4.1. Initiation of motion3.4.2. Sediment transport under equilibrium3.4.3. Non-equilibirium sediment transport3.5. Modelling aspects3.6. Sediment transport models 4. Assessment of parameters for canal design4.1. Background4.2. Irrigation water demand and scheduling4.3. Estimation of design discharge4.4. Flow control and sediment movement4.4.1. Flow control4.4.2. Sediment movement4.5. Roughness prediction4.5.1. General4.5.2. Roughness in the bed4.5.3. Roughness in the sides4.5.4. Equivalent roughness4.6. Sediment transport in non-wide canals4.6.1. Effects of canal geometry and flow characteristics in sediment transport4.6.2. Velocity distribution in a trapezoidal canal4.6.3. Exponent of velocity in sediment transport equation4.6.4. Correction factor4.6.5. Predictability of predictors with correction4.7. Conclusions5. Towards a new design approach5.1. General 5.2. Hydraulic aspects of canal design5.2.1. Existing canal design approaches in Nepal5.2.2. Canal design methods in SMIS5.2.3. Proposed canal design approach5.3. Management aspect of canal design5.3.1. Operation aspect5.3.2. Conveyance aspect5.3.3. Provision of settling pockets5.3.4. Maintenance activities5.4. Modelling aspect of canal design 5.5. Conclusions6. Model development6.1. Background6.2. Water flow 6.3. Sediment movement6.3.1. Galappatti's depth integrated model for non-equilibrium sediment transport6.3.2. Equilibrium sediment transport predictors6.3.3. Framework for concentration prediction6.4. Roughness prediction6.4.1. Roughness in the sides6.5. Canal structures and schematization6.5.1. General6.5.2. Hydraulics of flow control structures6.5.3. Discharge calculation in upstream control6.5.4. General remarks6.6. Morphological change and numerical scheme7. Data collection and scheme analysis7.1. Definitions and canal nomenclature7.2. Water requirements and design7.2.1. Irrigation water requirements7.2.2. Water delivery plan7.2.3. Canal alignment, control and design7.3. Morphological and geometrical data7.4. Water flow data7.4.1. Rotation schedule7.4.2. Calibration of broad crested weir7.5. Sediment data7.6. Conclusions8. Application of improved design approach8.1. General8.2. Evaluation of the model SETRIC8.2.1. Model verification8.2.2. Model calibration8.2.3. Model validation8.2.4. Predictability of equilibrium predictors8.3. Canal design aspects8.4. Management aspects8.4.1. Design water delivery schedule with constant water inflow8.4.2. Measured water inflow, sediment inflow and water delivery schedule8.4.3. Proposed water delivery schedule with changing demand8.4.4. Proposed water delivery schedule with variable inflow of water and sediment8.4.5. Effects of flow control in sediment transport9. Evaluation9.1. General9.2. Canal design aspects for sediment transport9.3. Mathematical modelling aspects of canal design9.4. The Model SETRIC9.5. Present canal design methods for sediment control in Nepal9.6. Modernization aspects of Sunsari Morang Irrigation Scheme9.7. Application of the improved approach for the design in SMIS9.8. Effects of flow control in sediment transport9.9. General observations and recommendations for further researchAppendix A: Flow diagramsAppendix B: Water and sediment dataAppendix C: Predictor-corrector methodAppendix D: Galappatti's depth integrated model for non-equilibrium sediment transport

O autorze

Krishna P. Paudel graduated in civil engineering with honours from the University of Roorkee (now IIT Roorkee), India in 1989. In January 2004, he joined the Core Land and Water Development of UNESCO-IHE, the Netherlands as a PhD research fellow. His thesis entitled: "Role of Sediment in the design and management of irrigation canals: Sunsari Morang Irrigation Scheme, Nepal" has made an assessment of existing canal design methods from sediment transport perspective. He has extensive experience in planning, design and management of irrigation and flood control works. Currently, Mr. Paudel is associated with CMS Nepal (Development Consultants) as Senior Water Resources Engineer and has been involved in the design as well as construction of different irrigation and water resource development projects. His field of interest are hydraulics, sediment transport and mathematical modelling.