Climate Change Impacts on Hydropower Generation in the Myitnge River Basin, Myanmar
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Hydropower'15 Stavanger, Norway 15-16 June 2015 Assessing Climate Change Impacts on Hydropower Generation in the Myitnge River Basin, Myanmar Min Khaing Director, Department of Hydropower Implementation, Ministry of Electric Power, Myanmar ABSTRACT Climate parameters such as temperature and precipitation are expected to change in the future and could significantly impact the hydrology of river basins. Changes in amount, timing and frequency of streamflow influence hydropower generation. This study was conducted to assess the climate change impacts on streamflow and hydropower generation in the Myitnge river basin. The Myitnge river basin is located in the northern part of the Republic of the Union of Myanmar and covers a total area of 30,800 km2. There are two numbers of reservoir type hydropower plants in this basin, namely, Yeywa, installed capacity 790MW and Upper Yeywa, installed capacity 280MW. Future climate parameters were projected from five general circulation models of CMIP-5 archive for RCP4.5 and 8.5. The hydrologic model (HEC-HMS) was applied in the study of the future changes in hydrological regimes especially in the annual and monthly inflow. The long term-average annual discharge is projected to decrease in GFDL-CM3 and MIROC-ESM-CHEM for all time periods. But MIROC-ESM, MPI-ESM- LR and MPI-ESM-MR show mixed trends. The intra-annual (monthly) changes in the river discharge are greater as compared to the annual discharges changes. HEC-ResSim, the reservoir simulation model was applied to examine how hydropower generation can vary for future climate scenarios. Future power production of the basin is expected to decrease under GFDL-CM3 and MIROC-ESM-CHEM. However, other three climate models have mixed trend in future hydropower production. The remarkable decreasing trend is observed in RCP8.5 of GFDL- CM3 with the ranges 13~25% and 18~23% in Yeywa and Upper Yeywa respectively. The analyses show that adaptation to the future climate scenarios is essential to optimal hydropower production in this river basin. 1. INTRODUCTION Hydropower as a renewable and sustainable electric energy provider is closely linked to the hydrological situation of a certain region (Koch et al. 2011). Hydropower is the most vulnerable energy source to change in global and regional climate because of its direct dependence on the magnitude and timing of streamflow (Jamali et al. 2013). Therefore, the assessment of climate change impact on hydropower generation to the future climate scenarios is crucial. Myanmar is one of the most vulnerable countries to climate change in Asia and Pacific in term of the indicator values of exposure such as change in temperature and precipitation and adaptive capacity such as poverty (ADB, 2009). One of the most important concerns related to climate change impact on streamflow in Myanmar is the implication of hydropower generation. The country relies mainly on the renewable energy, and hydropower sector is responsible for more than 55% of Myanmar’s electric power generation. Therefore, the impacts of climate change on the hydropower production and adaptation strategies are critical research area of Myanmar. 2. STUDY AREA AND DATASETS 2.1 BASIN DESCRIPTION The Myitnge River, one of the tributaries of the Ayeyarwady River, originates from Mount Loi Swang at an elevation of 1,460 m on the northern Shan Plateau. The Mytinge river basin is located approximately between the latitude 20°51’N ~ 23°48’ N and the longitude 96°23’E ~ 98°22’ E (Fig.1). It covers the north-west part of the Shan state and touches the Mandalay division at the downstream part near the confluence of the Ayeyarwady River. The Myitnge river basin is characterized by two seasons: a rainy season from Mid of May to October and a dry season from November to Mid of May. In particular, the period from November until February is cold and from March until April is hot. Monsoon climates, southwest and northeast ones, distinguish the climate of the basin area between wet and dry seasons. The southwest monsoon brings most rainfall of the basin from June until October; however, its effect on the basin is considerably moderated by its passage across the coastal hill ranges. The dry season, from November until Mid May, derives from the northeast monsoon and rainfall during this period comes Hydropower'15 Stavanger, Norway 15-16 June 2015 to practically zero (0). During the rainy season, the rainy days last consecutively for 90 to 120 days, resulting in the flood occurrence with long duration in the Myitnge River. Fig.1: Myitnge river basin and location of Yeywa and Upper Yeywa hydropower plants 2.2 AVAILABLE DATA For the Myitnge river basin, a digital elevation model (DEM) derived from U.S Geological Survey Global Data Explore (http:// www. gdex.cr.usgs.gov/) with 30m resolution. Soil parameters were derived from the Digital Soil Map of the world (Version 3.6) of the Food and Agriculture Organization (FAO). Land use data was collected from the Joint Research Center of European Commission website (http://bioral.jrc.ec.europa.eu/products/). OBSERVED HYDRO-METEOROLOGICAL DATA Daily precipitation data, for the period of 1981-2005, of eleven stations was collected from the Department of Meteorology and Hydrology, and Department of Hydropower Implementation, Myanmar. Minimum and maximum temperature data were only available for Hsipaw, Kyaukme, Kyaukse, Lashio, Mandalay and Naungcho stations. Daily discharge data from Salin (Yeywa) gauging station was obtained from two departments. The daily time series discharge for both stations were available for the period 1981 to 2005. CLIMATE MODEL DATA For this study five general circulation models (GCM) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) were selected to study the uncertainty in the climate change projections. Daily precipitation, maximum temperature and minimum temperature of selected GCMs were downloaded from the CMIP5 data portal (http://pcmdi9.llnl.gov/). In this study the RCP4.5 and 8.5scenarios were used for all 5 GCMs to cover the low, medium, and high end of possible future climate projections. Table -1: Selected Global Climate Models from CMIP5 archive Emission Climate model Institute/ organization Duration scenario 1981~2005 GFDL-CM3 Geophysical Fluid Dynamics Laboratory RCP 4.5, 8.5 2006~2100 Atmosphere and Ocean Research Institute (The 1981~2005 MIROC-ESM RCP 4.5, 8.5 University of Tokyo), National Institute for 2006~2100 MIROC-ESM- Environmental Studies, and Japan Agency for 1981~2005 RCP 4.5, 8.5 CHEM Marine-Earth Science and Technology 2006~2100 1981~2005 MPI-ESM-LR RCP 4.5, 8.5 2006~2100 Max Planck Institute for Meteorology (MPI-M) 1981~2005 MPI-ESM-MR RCP 4.5, 8.5 2006~2100 Hydropower'15 Stavanger, Norway 15-16 June 2015 RESERVOIR AND HYDROPOWER DATA The Yeywa reservoir and hydropower plant is located on the downstream stretch of the Myitnge River, about 50km southeast of Mandalay, the second largest city of Myanmar in air-distance. Average annual inflow into the reservoir is 15231MCM/year and the gross storage and effective storage capacity of the reservoir are 2630MCM and 1630MCM respectively. Yeywa hydropower plant is located just downstream of the reservoir and the installed capacity is 790 MW and the total annual generating capacity is 3550 GWh. The reservoir operation data were collected from the Department of Hydropower Implementation and Hydropower Generation Enterprise under the Ministry of Electric Power, Myanmar. The first unit operation was started in July2010 and the electricity is connected to the national grid. The power plant was commissioned in December 2010. But the daily operating data such as inflow, water level, spill, turbine discharge, power production, energy generation and operating hours were collected from July 2010 to the end of 2013. The Upper Yeywa reservoir and hydropower plant is located in the Kyaukme District of the Northern Shan State and about 1300km upstream of Yeywa reservoir and hydropower plant. Average annual inflow into the reservoir is 11479MCM/year but the gross storage and effective storage capacity of the reservoir are only 341MCM and 196MCM respectively. Main objective of the project is the hydropower generation only and the installed capacity is 280 MW and the total annual generating capacity is 1409 GWh. At present, the project is under construction stage; therefore, the data for reservoir operation and hydropower production are not available. Nevertheless, the data of design stage such as reservoir capacity curve, inflow, calculated hydropower production and others can be collected. Table -2: Salient features of Yeywa and Upper Yeywa reservoir Particular Yeywa Upper Yeywa Annual inflow 15231MCM 11479MCM Reservoir Full tank level EL 185m EL 395m Gross storage capacity 2630MCM 341.44MCM Effective storage capacity 1630MCM 196.18MCM Minimum operation level EL 148m EL 385m Features of dam Dam type RCC Dam Concrete Dam Crest elevation EL 197m EL 398m Dam height and length 132 m and 690 m 97 m and 247 m Features of power plant Installed capacity 790 MW (187.5 MW x 4 units) 280 MW (70 MW x 4 units) Commissioning date December, 2010 Under construction 3. METHODOLOGY 3.1 CLIMATE MODEL DOWNSCALING General circulation models and regional climate models are the important tools to project the expected future scenarios of climatic parameters. But the spatial resolutions of GCMs are too coarse for basin scale hydrologic modeling. Therefore, it is necessary to do downscaling the climate variables. Linear scaling method (Teutschbein & Seibert, 2012) for temperature and local intensity scaling method (Teutschbein & Seibert, 2012) for precipitation are utilized for downscaling of the climate variables. For the linear scaling of temperature, firstly, changes in the monthly GCM data between a base period (1981-2005) and future period were calculated for each month. Linear scaling factor was calculated using Eq.