Hydrologic Characteristics of a Drained Tropical Peat Catchment: Runoff Coefficients, Water Table and Flow Duration Curves

Abstract

Penebusgunaan serta penyaliran lembangan bertanah gambut merupakan suatu kerja pembangunan tanah yang penting di Malaysia. Kefahaman yang jelas terhadap sifat-sifat hidrologi lembangan tanah gambut bersaliran adalah faktor perlu ke arah pengurusan optimum sumber tersebut. Data-data hidrologi daripada lembangan bertanah gambut di Parit Madirono, Johor, Malaysia, telah di kutip dan digunakan untuk mencirikan hidrologi lembangan tersebut. Pencirian hidrologi telah dibuat menggunakan pendekatan hidrologi kuantitatif biasa. Perubahan dalam magnitud komponen-komponen hidrologi kawasan kajian telah ditentukan. Kawasan kajian mengalami variasi pekali air larian yang besar, menunjukkan bahawa lembangan tanah gambut bersaliran merupakan satu sistem hidrologi yang amat dinamik. Penurunan nilai pekali air larian tahunan yang amat ketara telah didapati. Nilai pekali air larian tahunan juga besar, pada julat 0.32 ke 0.92. Ini menunjukan bahawa hidrologi kawasan kajian amat dinamik, amat telap air dan sangat ‘flashy’. Keadaan aliran rendah juga sangat kecil tetapi meningkat mengikut masa, menunjukkan bahawa kawasan tadahan tidak mampu menampung aliran semasa cuaca kemarau. Nilai paras air tanah purata tahunan didapati mengurang pada kadar 2.7 cm setahun. Kata kunci: Hidrologi; tanah gambut tropika; lengkung aliran; lengkung paras air tanah Reclamation and drainage of peat basin is an important land development in Malaysia. A clear understanding on the hydrologic behavior of a drained peat basin is the essential factor towards an optimal management of the resource. Hydrological data from Madirono peat catchment located in Johor State, Malaysia was collected and used to characterize its hydrologic characteristics. The characterizations were made using the ordinary quantitative hydrologic approach. The magnitude of changes in the major hydrologic component of the study catchment was quantified. The study catchment experienced a large variation in runoff coefficient, indicating that a drained peat basin is a highly dynamic hydrologic system. A decaying trend in the annual runoff coefficient was observed. The annual runoff coefficients were large, ranging from 0.32 to 0.92. This indicates that the hydrology of the study catchment was extremely dynamics, highly permeable and very flashy. The low flow condition of the basin was extremely small but improving over time indicating that the basin could not sustain river flow during dry spell. The mean annual water table decreased over time by 2.7 cm per year. Key words: Hydrology; tropical peat; flow duration curve; water level duration curve