Bulletin of the Geological Society of Malaysia, Volume 46, May 2003, pp. 291 – 293

Preliminary analysis of recession flow characteristics of granitic catchments

WAN NOR AZMIN SULAIMAN, MOHD FIRUZ RAMLI, MOHD KHAIR KAMARUDDIN AND MOHD KAMIL YUSOFF

Department of Environmental Sciences, Universiti Putra Malaysia, 43400, UPM Serdang, Selangor

Abstract: Even though granite formation in Peninsular Malaysia has been generally known as poor aquifers, their ability to sustain river flow during periods of less or no rainfall has not been generally evaluated. Obviously, quantitative assessment about groundwater storages and their releasing rates especially during dry weather period form the basis for development and optimal utilization of our water resources.

The magnitude and variability of recession flows from a catchment depend upon many factors. However it has been commonly assumed that recession flows are less dependent upon precipitation and intensity distribution than physical storage of a catchment. Since, characteristically, these flows are more or less steady, it has been a common practice to represent them by general mathematical models. In this study an attempt has been made to evaluate the recession flow characteristics of two granitic catchments viz Sungai Lui (68.1 km²) and Sungai Semenyih at Kg. Rinching in Selangor, (225 km²). Both catchments have similar characteristics for soil cover which is derived from weathered granite or granite parent material

Basically, slopes of individual recession hydrographs were determined and based on selected 39 and 49 recession hydrographs for Sg. Semenyih, and Sungai Lui respectively, it was found that the average recession coefficient for the Sg Lui and Sungai Rinching is 0.0463 and 0.0315 day^·1 respectively. The exponential function model used to the described the recession flow of the two rivers was Q_t = Q_oe^-αt, where α is the recession coefficient.

Abstrak: Formasi granit di Semenanjung Malaysia diketahui umum sebagai akuifer yang kurang baik. Namun, maklumat tentang keupayaan formasi berkenaan sebagai penyumbang kepada aliran sungai semasa ketiadaan hujan atau kemarau panjang tidak diketahui dengan jelas. Penilaian secara kuantitatif terhadap simpanan air tanah dan kadar pelepasannya ke sungai terutama di musim kering merupakan asas kepada pembangunan dan penggunaan optimal sumber air.

Magnitud dan perubahan alir rosotan dari sebuah kawasan lembangan bergantung kepada banyak faktor. Walaubagaimana pun, andaian umum ialah alir rosotan kurang bergantung kepada pertaburan curahan dan keamatan hujan tetapi lebih kepada simpanan fisikal kawasan lembangan. Oleh kerana ciri-ciri aliran rosotan boleh dikatakan mantap, adalah menjadi kebiasaan ianya diwakili dengan model metamatik. Dalam kajian ini percubaan telah dilakukan untuk menilai ciri-ciri alir rosotan yang mewakili dua buah kawasan lembangan iaitu Sungai Lui (68.1 km²) dan Sungai Semenyih (225 km²). Kedua kawasan lembangan ini mempunyai ciri permukaan tanah yang sama iaitu terbitan dari granit terluluhawa atau bahan granit induk.

 Pada asasnya, cerun setiap hidrograf rosotan ditentukan dan berdasarkan kepada 39 hidrograf rosotan bagi Sungai Semenyih dan 49 bagi Sungai Lui, didapati purata koefisien rosotan bagi Sungai Lui ialah 0.0463 hari^·1 dan Sg Semenyih ialah 0.0315 hari^-1. Model fungsi exponen yang diguna bagi menghuraikan alir rosotan bagi kedua sungai berkenaan ialah Q_t = Q_oe^-αt, di mana α ialah koefisien sorotan.

https://doi.org/10.7186/bgsm46200348