The downstream region of the Kuantan River has a high potential of being affected by salinity issues according to research conducted nearly 40 years ago in studying the salinity effects on the freshwater intake in Kobat. The resulting results from the study then lead to the construction of a barrage in 1985 to prevent salt intrusion into the Kobat freshwater intake station area during low flow and high tides.

However, salt intrusion problems were reported to occur in recent years. Thus, this research aims to: 1) determine salt intrusion extends in the Kuantan Estuary after the construction of the barrage; 2) calibrate and validate the Van der Burgh Coefficient K, and dispersion coefficient D in determining the salt intrusion pattern; and 3) compare the salinity pattern before and after the construction of the barrage. A 1-D analytical salt intrusion model was adopted in this study for the salinity analysis. Field measurements were conducted along the dry season at spring tide when the salinity travels furthest with a minimal amount of freshwater discharge. Salinity data was collected only up to the Kobat barrage by using the moving boat. The total salinity length at HWS obtained for 27th & 29th March 2017, 3rd October 2017, 7th March 2018 and 15th April 2018 are 21 km, 18.82 km, 21.05 km, 16.24 km, and 24 km, respectively. Results obtained from the salt intrusion simulation showed that the Van der Burgh Coefficient K for Kuantan Estuary is 0.45 and the dispersion ranged between 100 and 250 m2/s. Meanwhile, the comparisons of the newly surveyed salinity results with the previous research have indicated that the pattern of longitudinal salinity distribution has significantly changed after the construction of the barrage. The finding from the recent survey demonstrated the scatter distribution pattern compared to the gradually uniform pattern in the previous survey. This condition shows that the natural hydrodynamic process in the Kuantan Estuary has no longer in equilibrium condition and is unstable. The validation results obtained show good agreement between the simulated and observed salinity distribution in the estuary with low RMSE in the range 0.4 ppt–5.0 ppt and high NSE values ranges 0.97 to 1.00. This indicates that the model is reliable and can become an important tool for water managers in conducting salt intrusion studies for this area.

根据近 40 年前在研究盐度对 Kobat 淡水摄入量的影响时进行的研究，关丹河下游地区很可能受到盐度问题的影响。研究的结果随后导致在 1985 年建造了一个拦河坝，以防止盐分在低流量和高潮时侵入 Kobat 淡水取水站区域。

然而，据报道，近年来发生了盐入侵问题。因此，本研究的目的是：1）确定拦河坝建成后关丹河口盐分侵入的范围；2) 校准和验证范德堡系数 K 和色散系数 D 在确定盐入侵模式时；3) 对比拦河坝施工前后的盐度分布情况。本研究采用一维分析盐侵入模型进行盐度分析。实地测量是在大潮的旱季进行的，此时盐度最远，淡水排放量最少。盐度数据仅通过移动船收集到 Kobat 拦河坝。2017 年 3 月 27 日和 29 日、2017 年 10 月 3 日获得的 HWS 总盐度长度，2018年3月7日和2018年4月15日分别为21公里、18.82公里、21.05公里、16.24公里和24公里。从盐侵入模拟获得的结果表明，关丹河口的范德堡系数 K 为 0.45，扩散范围在 100 到 250 m2/s 之间。同时，新调查的盐度结果与前人研究的对比表明，拦河坝建成后，盐度的纵向分布格局发生了显着变化。最近调查的结果表明，与上次调查中逐渐均匀的模式相比，散布分布模式。这种情况表明，关丹河口的自然水动力过程已不再处于平衡状态，处于不稳定状态。获得的验证结果表明，在河口模拟和观察到的盐度分布之间具有良好的一致性，低 RMSE 范围为 0.4 ppt-5.0 ppt，高 NSE 值范围为 0.97 到 1.00。这表明该模型是可靠的，可以成为水资源管理者进行该地区盐入侵研究的重要工具。