C207

Impact of Upstream Reservoir System on Downstream Water Level:
A Case Study in the Vu Gia - Thu Bon River Basin, Central Vietnam〇Bui Thi Phuong THAO, Sameh A. KANTOUSH, Nguyen Quang BINH, Tetsuya SUMI, Mohamed SABER,
Bui Du DUONG, Du Le Thuy TIEN
I. INTRODUCTION
Vietnam faces challenges in managing water resources,
particularly floods in the central region. Floods, aglobal natural disaster, cause annual damage. Vietnam
prioritizes

urbanization,increased

power

industrialization,generation.

Theandgovernment

strategically focuses on water resource development
for electricity, agriculture, and flood control. Damconstruction disrupts river flow, impacting water level
fluctuation patterns. Reservoirs play a crucial role incontrolling downstream flood risk during the rainy

Figure 1: Vu Gia Thu Bon River Basinseason. However, the collateral effects of hydraulicIII. METHODOLOGY

structures, like dams, require careful consideration. A

This study assesses the Hydrological Predictions for thecomprehensive assessment of reservoir operations andEnvironment

their impact on water level fluctuations is crucial. This

simulating reservoir operations. Calibration andstudy aims to evaluate the influence of the Upstream

validation against observed pre-dam (2000–2009) andReservoir System on the Downstream Water Level inpost-dam (2016–2020) streamflow and water levels are

the Vu Gia - Thu Bon River Basin (VGTBRB) in

conducted. Theoretical integration of an Integrated

Central Vietnam.

Reservoir Operation System (IROS) (Du et al (2022))(HYPE)

model's

performanceinis explored, focusing on Qout calculation. Performance
II. STUDY AREA

indices (NSE, KGE) gauge the model's reliability in

The VGTB River basin, a vital internal drainage system

replicatingin Vietnam's central region (see Figure 1), spans 10,000

contributing valuable insights into its effectiveness inkm2. It includes the Vu Gia (204 km) and Thu Bon (152

simulating integrated reservoir operations.

km) rivers. The topography ranges from 0 m to 2598 m

IV. RESULTS

elevation, with approximately 50% forest cover,For pre-dam period, the HYPE model was calibrated

followed by agriculture, urban areas, and water bodies.

(2000-2005) and validated (2006-2009) at two

The basin features 18 multipurpose dams forhydrological stations, Nong Son and Thanh My, foragriculture, hydropower, and water supply, along with

discharge and water level predictions. Figure 2 (a, b, c,2 water discharge and 16 rainfall stations.The wetd) and the corresponding evaluation indicators reveal

season (September to December) poses a flood risk duethat the HYPE model exhibits satisfactory simulation

to substantial rainfall, while the dry season (February

results at both hydrological stations within the VGTBto August) experiences minimal rainfall and periodic

river basin. During the 2010-2020 period, simulations

water shortages.

were conducted to analyze water levels in the VGTB

observedhydrologicalpatterns,river basin, focusing on the Ai Nghia and Giao Thuymodeling is needed to understand its specific impacts

stations with and without reservoirs. The results fromcomprehensively.

Figure 3 show that, throughout the year, the simulated

REFERENCE: Du, T. L. T. et al (2022). Streamflow

water levels with a reservoir are consistently lower thanPrediction in Highly Regulated, Transboundary

without at both stations. This indicates the reservoir's

Watersheds Using Multi-Basin Modeling and Remote

effectiveness in mitigating flood risks during the flood

Sensing Imagery. Water Resources Research, 58(3)season. However, a negative impact is observed during

ACKNOWLEDGMENT: Supporting of the sponsors

the dry season, emphasizing environmental concerns.

withIn conclusion, while the reservoir proves effective inMAnagement

reducing downstream water levels and preventing

development (FSMART)'' funded by Asia-Pacificfloods, further research incorporating hydraulic

Network for Global Change Research

Project:''IntegratedinFloodRiver basinsandfor

Sediment
susTainable