ENVIRONMENTAL FLOW MODELLING AS A TOOL FOR WATER RESOURCES MANAGEMENT: A STUDY OF DETAILED ENVIRONMENTAL IMPACT ASSESSMENT (DEIA) IN SUNGAI PELUS CATCHMENT, MALAYSIA (Permodelan Aliran Persekitaran sebagai alat kepada pengurusan sumber air: Kajian Terperinci Penilaian Impak Alam Sekitar di Lembangan Sungai Pelus, Malaysia)

Abstract

In Detailed Environmental Impact Assessment (DEIA), modeling of environmental flows is one of the
main studies that need to be delivered in the final DEIA report. The model is important to the project
proponent to engage suitable designs that can be suited to environmental needs, particularly on future
water resources management. In this respect, Environmental Flow Assessment (EFA) is used to
estimate the quantity and timing of flows to sustain the ecosystem values. The proposed of
hydropower projects in Sg Pelus, Perak was studied aimed to evaluate existing river flow
characteristics and to model EFA due to river diversion of Sg Pelus. Daily river flow (m3/s) recorded
at Sg Pelus (Station No. 6035) and Sg. Yum (Station No. 6044) gauging stations were used to design
the flow duration curve. The low flow then calculated using the 7Q10 equation to estimate the lowest
7-day average flow that occurred on average once every 10 years. The results indicate that the average
daily flows for both stations (6035 and 6044) are 5.080 m3/s and 11.391 m3/s, respectively. The flow
duration curve shows that 50 percent of 4 m3/s of discharge will be exceeded/ equaled in Station 6044
while 8.2 m3/s of discharge will be exceeded or equaled in Station 6035. The requirement
environmental flows for both parameters are 0.613 and 0.426 m3/s for Environmental Flow
Assessment, respectively. The results obtained in this model are important to managing the river at
least in Class II after river diversion project.