ROLE OF RESERVOIR OPERATION IN SUSTAINABLE WATER SUPPLY TO SUBAK IRRIGATION SCHEMES IN YEH HO RIVER BASIN Mawiti Infantri Yekti Thesis committee Promotor Prof. Dr E. Schultz Emeritus Professor of Land and Water Development UNESCO-IHE Institute for Water Education Delft, the Netherlands Co-promotors Prof. Dr I Nyoman Norken Department of Civil Engineering Faculty of Engineering, Udayana University Bali, Indonesia Dr László Hayde Chair group Land and Water Development Department of Water Sciences and Engineering UNESCO-IHE Institute for Water Education Delft, the Netherlands Other members Prof. Dr R. Uijlenhoet, Wageningen University & Research Prof. Dr N.C. van de Giesen, Delft University of Technology Prof. Dr I Wayan Windia, Udayana University, Bali, Indonesia Prof. Dr P. van der Zaag, UNESCO-IHE, Delft, the Netherlands This research was conducted under the auspices of the SENSE Research School for Socio- Economic and Natural Sciences of the Environment ROLE OF RESERVOIR OPERATION IN SUSTAINABLE WATER SUPPLY TO SUBAK IRRIGATION SCHEMES IN YEH HO RIVER BASIN Thesis submitted in fulfilment of the requirements of the Academic Board of Wageningen University and the Academic Board of the UNESCO-IHE Institute for Water Education for the degree of doctor to be defended in public on Thursday 1 June, 2017 at 11:30 a.m. in Delft, the Netherlands by Mawiti Infantri Yekti Born in Jember, Indonesia CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business  2017, Mawiti Infantri Yekti All rights reserved. No part of this publication or the information contained here in may be replaced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without written prior permission from the publisher. Although care is taken to ensure the integrity and quality of this publication and the information therein, no responsibility is assumed by the publishers nor the author for any damage to property or persons as a result of operation or use of this publication and/or the information contained herein. Published by CRC Press/Balkema PO Box 11320, 2301 EH Leiden, The Netherlands e-mail: [email protected] www.crcpress.com - www.taylorandfrancis.com ISBN 978-1-138-06543-7 (Taylor & Francis Group) ISBN 978-94-6343-083-8 (Wageningen University) DOI: http://dx.doi.org/10.18174/404538 Table of contents Table of contents .............................................................................................................. v Acknowledgements ......................................................................................................... ix 1 Introduction ................................................................................................................ 1 2 Background and objectives ........................................................................................ 7 2.1 Profile of the region.......................................................................................... 7 2.2 Water resources .............................................................................................. 11 2.2.1 World water resources ........................................................................... 11 2.2.2 Water resources in Indonesia ................................................................ 13 2.2.3 Water management in Indonesia ........................................................... 14 2.2.4 Water resources in Bali ......................................................................... 16 2.3 Definition of Subak irrigation schemes .......................................................... 17 2.4 Subak schemes ............................................................................................... 19 2.4.1 Paddy terraces ....................................................................................... 19 2.4.2 Subak irrigation system ......................................................................... 21 2.5 Subak cultivation area .................................................................................... 23 2.6 Previous studies on water management of Subak irrigation schemes ............ 23 2.7 Problem description........................................................................................ 26 2.8 Objectives ....................................................................................................... 29 2.8.1 Research questions ................................................................................ 29 2.8.2 Hypotheses ............................................................................................ 29 2.8.3 Research objectives ............................................................................... 31 3 Development of Subak irrigation schemes: learning from experiences of ancient Subak schemes for participatory irrigation system management in Bali .... 33 3.1 Introduction .................................................................................................... 33 3.2 Method and discussion ................................................................................... 36 3.2.1 PIM in irrigation system operation and maintenance ........................... 39 3.2.2 PIM with respect to socio-culture and economics of agriculture .......... 45 3.2.3 PIM in light of a religious community .................................................. 51 3.3 Result and conclusion..................................................................................... 54 vi Reservoir operation for water supply to Subak irrigation schemes in Yeh Ho River Basin 4 Subak in the south of Bali: discharge analysis for a system approach to river basin development with Subak irrigation schemes as a culture heritage ................ 57 4.1 Introduction .................................................................................................... 57 4.2 Study of a river basin ..................................................................................... 57 4.3 Managed flow approach in Yeh Ho River Basin ........................................... 59 4.4 Method and material....................................................................................... 59 4.5 Results and discussion .................................................................................... 62 4.6 Conclusion ...................................................................................................... 73 5 Hydrology and hydraulic approaches: irrigation-drainage of Subak irrigation schemes, a farmer's perspective over a thousand years ........................................... 77 5.1 Introduction .................................................................................................... 77 5.2 Methodology .................................................................................................. 78 5.2.1 Observation of the water balance in a paddy terraces block ................. 80 5.3 Results and discussion .................................................................................... 80 5.4 Conclusion ...................................................................................................... 87 6 Model simulations and optimisation technique ....................................................... 89 6.1 Model categorization ...................................................................................... 89 6.2 Modelling of Subak schemes related to Tri Hita Karana philosophy ........... 91 6.3 Multiple purpose reservoir operation ............................................................. 92 6.4 Scenario analysis in Subak schemes .............................................................. 92 6.5 Simulations with the RIBASIM model .......................................................... 94 6.6 Application aspects of the RIBASIM model ................................................. 95 6.7 Yeh Ho River system as input in the RIBASIM model ................................. 97 7 Scenario analysis ................................................................................................... 101 7.1 Hydrologic and hydraulic analysis ............................................................... 101 7.1.1 Analysis of rainfall data: dependable rainfall and effective rainfall ... 102 7.1.2 Streamflow analysis ............................................................................ 104 7.1.3 Potential evapotranspiration ................................................................ 104 7.1.4 Reservoir water surface losses and gains ............................................ 105 7.1.5 Other reservoir losses and gains .......................................................... 106 7.1.6 Reservoir elevation/storage/area relationship ..................................... 106 Table of contents vii 7.1.7 Flow routing in the reservoir and hydraulic profile of outlets ............ 107 7.1.8 Evaluation of reservoir lifetime based on sedimentation .................... 107 7.2 Advanced irrigation node in RIBASIM ....................................................... 108 7.2.1 Schematization of the irrigated area .................................................... 109 7.2.2 Interactive graphical cropping plan editor .......................................... 111 7.2.3 Simulation of a cropping plan ............................................................. 113 7.2.4 Soil moisture characteristics ............................................................... 114 7.2.5 Crop water requirement in a paddy terraces block .............................. 118 7.2.6 Computation of command area water demand, actual field water balance and effective irrigation water supply ..................................... 122 7.3 Results of economic evaluation of storage allocation .................................. 125 7.3.1 Pricing of paddy productivity .............................................................. 125 7.3.2 Pricing of domestic water .................................................................... 126 7.4 Scenario analysis, simulation and optimisation of Yeh Ho River Basin ..... 129 7.4.1 Simulation of the first scenario ........................................................... 131 7.4.2 Simulation of the second scenario ....................................................... 136 7.4.3 Simulation of the third scenario .......................................................... 140 7.4.4 Simulation of the fourth scenario ........................................................ 145 7.4.5 Simulation of the fifth scenario ........................................................... 149 7.5 Summary of the simulation and optimisation of Yeh Ho River Basin ........ 155 7.5.1 Utilisation of hydraulic structures ....................................................... 155 7.5.2 Verification of the model .................................................................... 156 8 Evaluation .............................................................................................................. 159 8.1 Recommendations for river basin development ........................................... 159 8.1.1 Telaga Tunjung Reservoir operation based on Subak cropping patterns ................................................................................................ 160 8.1.2 Operation and maintenance of the Subak irrigation systems .............. 161 9 References .............................................................................................................. 163 viii Reservoir operation for water supply to Subak irrigation schemes in Yeh Ho River Basin APPENDICES A. Abbreviations and acronyms ................................................................................. 175 B. Symbols ................................................................................................................. 177 C. Surface runoff analysis as inflow to the Telaga Tunjung Reservoir ..................... 179 D. Analysis of rainfall data ......................................................................................... 181 E. Reference evapotranspiration ................................................................................ 183 F. Hydraulic profile of outlets .................................................................................... 195 G. Reservoir and its hydraulic structures .................................................................... 197 H. Information on reservoir sedimentation ................................................................. 199 I. Infiltration and percolation .................................................................................... 203 J. Results of the measurements in a paddy terraces block ........................................ 205 K. Graphs of scenario simulations with RIBASIM .................................................... 225 L. Summary ................................................................................................................ 235 M. Samenvatting ......................................................................................................... 241 N. About the author .................................................................................................... 247 Acknowledgements A PhD study is like a study of life itself. I started to look for a PhD scholarship by downloading the guideline of the PhD booklet at the Nuffic website in 2004. I had a dream that after being married and giving birth to two babies, I would pursue my study at a higher level. Before being married I had one request to my ex boyfriend that is now my husband. I did not want to have a big house, jewellery, or anything else material but just one thing, his permission to continue my study. I met him when I was a lecturer at Udayana University, Bali, Indonesia. The reason was simple, while I am a teacher I should have more knowledge to share with my students. As well when in the bachelor study I had a dream to study in the centre of water engineering science, the Netherlands, where is the best non-gravity drainage system in the world. In the PhD rules of the Netherlands Fellowship Programme (NFP), it is described that to become a PhD student at UNESCO-IHE, you should be graduated or have a master degree from UNESCO-IHE, or other institution in the Netherlands. Then I applied for a master study scholarship two times (2003 and 2004). Unfortunately, I did not pass it. Then in 2007, I got a NFP fellowship for a short course at UNESCO-IHE. Furthermore, in 2009, I was awarded a scholarship from the Indonesian Government, and I had registered already in the University of Wollongong, New South Wales, Australia. At the same time, my father was sick, and he asked me to accompany him for 21 days in the hospital, because he should have a surgery in his spinal column. Because of this I cancelled my starting time to study in Australia. Afterwards I had the plan that I would start the study in 2010. Unfortunately, at this year, I cancelled again my planning, because my parents went to Mecca. I relied on my parents to accompany my children when I am studying abroad. My reason was natural, as a mother and a wife I should manage the household first, even though in reality there can be unpredictable developments. I just tried to manage it best. Based on cancellation of starting times of my study, I thought deeply that I should change the type of study, from full time to a sandwich study. Then I applied for an NFP fellowship in early 2010. At that time, I finished all the administration and finances of the Indonesian Government Scholarship, which I had received after the announcement in