EVALUATION OF AN EXISTING AND FUTURE WATER BALANCE IN THE BAGO RIVER BASIN, MYANMAR

Abstract

In recent years, frequent flood to the Bago Township area was serious problems during the rainy season, however, drought occurs during the late of wet season and the dry season normally. In this study, Water Evaluation and Planning (WEAP) model was implemented in the Bago River Basin (BRB), Myanmar to evaluate an existing and future water balance, based on five different scenarios: Reference (RS), High Population Growth Rate (HPG), Higher Living Standard (HLS), Climate Change (CC), and Water Supply Management (WSM). The existing scenario was set for the year of 1999-2018, however, the model calibration in surface hydrology at the Bago gauging station in the Bago Township within the period of 2011-2015 and model verification during the period of 2016-2018 were carried out. The observed data during these periods were fitted to the coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE) and Root mean square error (RMSE) with the values of 0.97, 0.84, 9 m3/s and 0.98, 0.92, 4 m3/s, respectively. The mean annual water supply based on releasing flow from the existing five dams and actual rainfall-runoff during the period of 1999-2018 was 1,208 MCM, while the demand of water for domestic and agricultural as well as the diversion from BRB was 1,225 MCM. The existing results indicated that currently the basin has sufficient water to meet the water demands except in 2014 and 2018.

The simple statistics were adapted as forecasting of population in next 22 years (2019-2040) with the growth rate of 1.85 % with no changes for the others such as industrial, and agricultural area. The future annual water supply of projected reference scenario will be 1,097 MCM, and water demand will be 1,237 MCM. However, the annual unmet water demand will be started in 2021 due to shortage water. The future average monthly unmet demand under reference Scenario, high population growth and higher living standard scenario to be 7.88 MCM, climate change scenario impacted at 25.8 MCM, and WSM Scenario showed enormous improvement of a 0.03 MCM. The results show that, by reducing the water use rate of the summer crops, reducing transmission losses in the water supply site, and proper demand site management (DSM), unmet demand can be reduced expressively. The results further indicate that the WEAP model showed highly capable and the recommendation of WEAP should be applied in management agencies and local authorities in decision making for the improvement of Bago River Basin water demand and supply system efficiency in the future.

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