Impacts of Barrage Flushing and Flooding-in Operations on Saline Intrusion Upstream

• Published in: Journal of Civil Engineering, Science and Technology (Online) Vol. 2; no. 1; pp. 18 - 24
• Main Authors: I.N., Law, Y.W., Oon, P.L., Law, F.W.L., Kho
• Format: Journal Article
• Language: English
• Published: 01.03.2011
• ISSN: 2462-1382; 2462-1382
• DOI: 10.33736/jcest.83.2011

This research looks into the effects of barrage flushing and flooding-in operations on upstream salinity versus discharge over time. Water samples for salinity levels were collected over a period of 33 hours from two locations upstream of Sarawak Barrage, i.e., at 1.5 km and 6 km. During flooding-in operation, salinity levels increased by approximately 13.8 ppt at 1.5 km upstream, and by 0.2 ppt at 6 km upstream after 3 hours into the operation. At 6 km upstream, negligibly low saline levels ranging from 0.5 to 2.5 ppt were detected, regardless of sea tide levels and flow rates through barrage gates. Rate of saline water propagation towards upstream was estimated to be approximately 5 km/hour during flooding-in operation. During flushing operation, it was noticed that waters flowed smoothly from upstream through the barrage gates to downstream without generating noticeable turbulences, whereby salinity levels at 1.5 km upstream dropped from approximately 11.7 to 4.7 ppt over a period of 3 hours. After 3 hours of gates closure, it was observed that salinity levels upstream of the barrage dropped by approximately 1.4 ppt at Pending (1.5 km upstream), and by 0.5 ppt at Satok (6 km upstream). From this study, it was also found that the differences in the rates of increase and decrease in salinity levels at a particular point upstream of the barrage over a period of 3 hours during flooding-in and flushing operations were negligibly small (<1 ppt).