Sains Malaysiana 46(12)(2017): 2331–2338

http://dx.doi.org/10.17576/jsm-2017-4612-09

Pencirian Sifat Akuifer dalam Batuan Granit di Selangor

(Characterization of Aquifer Properties in Granite in Selangor)

HAMIZAH MOHAMAD & NORSYAFINA ROSLAN*

Program Geologi, Pusat Sains Sekitaran dan Sumber Alam, Fakulti Sains dan Teknologi

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

Diserahkan: 26 Oktober 2016/Diterima: 30 Jun 2017

ABSTRAK

Di Selangor, sumber air bawah tanah dijadikan sumber bekalan air alternatif bukan sahaja oleh pelbagai jenis industri malah untuk kegiatan kuari. Kebanyakan telaga abstraksi ini adalah di dalam akuifer batuan teretak sama ada di dalam batuan metasedimen ataupun batuan granit. Memandangkan terdapat pertambahan penggunaan air bawah tanah dari semasa ke semasa, adalah penting untuk mengetahui cirian akuifer batuan teretak terutamanya dalam batuan granit ini. Oleh itu, satu kajian telah dijalankan untuk mencirikan sifat akuifer dalam batuan granit di Selangor. Kaedah kajian melibatkan cerapan lapangan di kuari IJM Sungai Buloh dan analisis data lubang gerudi, ujian pengepaman dan analisis kimia air bagi semua telaga dalam batuan granit di Selangor. Hasil kajian menunjukkan bahawa kawasan kajian terdiri daripada akuifer retak terkekang hingga separa terkekang. Log telaga merekodkan kehadiran lapisan tanah baki yang terdiri daripada lempung berpasir hingga lempung keras dengan ketebalan sehingga 50 m. Lapisan bawah pula dilapisi oleh batuan granit teretak yang bertindak sebagai lapisan pengandung air. Kekar ditemui pada kedalaman 18 hingga 145 m. Analisis lineamen menunjukkan korelasi positif dengan analisis ketakselanjaran di lapangan; berarah timur laut - barat daya dan barat laut - tenggara, selaras dengan zon sesar Kuala Lumpur dan Bukit Tinggi. Nilai keterusan berjulat 2.6 hingga 36.1 m2/hari manakala julat kekonduksian hidraulik adalah 0.06 hingga 4.6 m/hari. Kadar luahan telaga adalah <10 m3/jam. Jumlah pepejal terlarutnya adalah rendah (<372 mg/L). Kehadiran retakan di dalam batuan granit akuifer ini telah membantu meningkatkan keupayaannya sebagai akuifer. Analisis kimia menunjukkan ada telaga yang berpotensi mengalami pencemaran.

Kata kunci: Akuifer bandaran; batuan teretak; granit

ABSTRACT

In Selangor, groundwater is used as an alternative water source in manufacturing industry and also for quarry activity. These abstraction wells are located in either fractured metasediment or granitic rock aquifer. It is important to understand the characteristic of fractured rock aquifer especially in granite due to its increasing demands. Therefore, this study aimed on characterizing the aquifer behavior in fractured granite in Selangor. The study methods used include detailed mapping at IJM Quarry at Sungai Buloh and analysis of well logs, pumping test analysis and well water chemistry for wells in granite in Selangor. The results showed that the aquifer type is confined to semi-confined aquifer. Well log indicates the presence of residual soil layers comprises of sandy clay to hard clay with thickness up to 50 m. The bottom layer is underlained by fractured granite which acts as water bearing layer. The fractures are observed at 18.27 to 144.9 m depth. Lineament analysis in study area shows a positive correlation with discontinuity analysis in the field in the direction of northeast-southwest and northwest-southeast, which is in line with Kuala Lumpur and Bukit Tinggi fault zone. Transmissivity values range from 2.6 to 36.1 m2/day while hydraulic conductivity values from 0.06 to 4.6 m/day. Well discharge rate is <10 m3/h. Total dissolved solids values are low (<372 mg/L). The fractures in granite have increased its capability as an aquifer. Chemistry analysis showed that there are possibility of few localized wells being polluted.

Keywords: Fractured rock; granite; urban aquifer

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*Pengarang untuk surat-menyurat; email: finalan@ukm.edu.my