Guidance for Efficient Irrigation Water Use in the Lower Mekong River Basin

Mekong River Commission Guidance for Efficient Irrigation Water Use in the Lower Mekong River Basin Consultant’s Report February 2010 Meeting the Needs, Keeping the Balance Mekong River Commission Guidance for Efficient Irrigation Water Use in the Lower Mekong River Basin Consultant’s report February 2010 Published in Vientiane, Lao PDR in February 2010 by the Mekong River Commission Cite this document as: MRC (2010) Guidance for Efficient Irrigation Water Use in the Lower Mekong River Basin, Consultant’s report, Mekong River Commission, Vientiane. 102 pp. The opinions and interpretation expressed within are those of the authors and do not necessarily reflect the views of the Mekong River Commission. Authors: N. Horikawa, T. Masumoto Editor: J. Simery Graphic design: J. Simery © Mekong River Commission 184 Fa Ngoum Road, Unit 18, Ban Sithane Neua, Sikhottabong District, Vientiane 01000, Lao PDR Telephone: (856 – 21) 263 263 Facsimile: (856 – 21) 263 264 E-mail: [email protected] Website: www.mrcmekong.org ii Table of contents Aknowledgements �� ix Abbreviations and acronyms �� xi 1. Introduction ��1 1.1 Scope of this guidance ��1 1.2 Limitations of this guidance ��2 1.3 Water loss in an irrigation system: origins and countermeasures ��3 1.4 Classification of irrigation in the LMB ��4 2. Seasonal irrigation planning ��7 2.1 Outline of seasonal irrigation plan ��7 2.2 Key issues for improving a seasonal irrigation plan ��9 3. Irrigation scheduling and facility operations ��25 3.1 Outline of irrigation scheduling ��25 3.2 Key issues to improve irrigation scheduling..................................................................28 3.3 Reservoir operations ��37 3.4 Canal operations ��38 4. Water management of tertiary canals ��51 4.1 Establishment of WUAs ��53 4.2 Prohibition of turnout operation by water users ��54 4.3 Intermittent water delivery to tertiary canals ��55 4.4 Enhancement of plot-to-plot irrigation practices ��56 5. Improvement of physical structures ��61 5.1 Installation of regulating reservoirs ��61 5.2 Installation of cross-regulators.......................................................................................61 5.3 Improvement of canal systems ��62 5.4 Construction of tertiary canals ��64 5.5 Installation of remote monitoring and control systems ��66 5.6 Installation of automatic gates ��67 5.7 Facilities for reuse of irrigation water............................................................................69 5.8 Construction of regulators and canal improvement in low-lying systems.....................70 6. Managerial and technical aspects ��73 6.1 Monitoring ��73 6.2 Water requirement ��74 6.3 Organisation ��77 iii 6.4 Role of maintenance �� 78 6.5 Institutional system design �� 79 References �� 83 Appendix: Case study �� 85 iv Table of figures Figure 1.1 Scope of the guidance for Efficient Irrigation Water Use in the Lower Mekong Basin .................................................................................................1 Figure 1.2 Water loss in an irrigation system: origins and countermeasures ...................3 Figure 1.3 Classification of irrigated lands in irrigation facilities in the LMB (0.1º mesh)(Shimizu et al.,2006) .....................................................................5 Figure 2.1 Procedure used for seasonal irrigation planning .............................................9 Figure 2.2 Water losses occurring along the boundaries of irrigated areas and canals ..13 Figure 2.3 Schematic diagrams of scattered and converged irrigation areas ..................14 Figure 2.4 Rotation of irrigated area ...............................................................................15 Figure 2.5 Rice growing periods and monthly precipitation in Muda, Malaysia (Yamaoka et al. 2004) ...................................................................................16 Figure 2.6 Extension of the irrigation period induced by delayed crop establishments .17 Figure 2.7 Effect of a distributed irrigation period on the peak demand of water at the start of the irrigation period .................................................................18 Figure 2.8 Example of a distributed irrigation period (Nanbu, 2002) ............................18 Figure 2.9 Control of water level in low-lying areas ......................................................21 Figure 2.10 Shifts in water level in a tidal irrigation system ............................................21 Figure 2.11 Water balance analysis (Kaneko, 1973) ........................................................22 Figure 2.12 Change of controlled water level in a flood-prone irrigation system ............23 Figure 2.13 Estimation of water intrusion in an inundated irrigation area .......................24 Figure 3.1 Comparison between seasonal irrigation planning and irrigation scheduling ......................................................................................................25 Figure 3.2 Water supply determined by irrigation scheduling .......................................26 v Figure 3.3 Bulletin board informing water users in each sub-irrigation system of the water delivery rotation at irrigation turnouts ......................................27 Figure 3.4 Comparison of flow in continuous and intermittent water supply methods ..29 Figure 3.5 Variation of the irrigation efficiency depending on the amount of water supplied ...............................................................................................29 Figure 3.6 Estimations of flow rates in continuous and intermittent supply methods. ...31 Figure 3.7 Example of factors that can be examined in field surveys ............................33 Figure 3.8 Overflow from a tertiary canal ......................................................................34 Figure 3.9 Flow chart of water delivery under the ordering system ...............................36 Figure 3.10 Constraint curves for reservoir operations ....................................................38 Figure 3.11 Changes in flow rates of diverted water with fluctuations in water level..... 40 Figure 3.12 Causes of water level fluctuations and countermeasures ..............................41 Figure 3.13 Operation from upstream to downstream in sequence ..................................42 Figure 3.14 Frequent gate operation .................................................................................43 Figure 3.15 Differences between flow rate and water level measurements ......................44 Figure 3.16 Estimation of travel time ..............................................................................46 Figure 3.17

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