Menganalisis aras kegersangan di Provinsi Sulawesi Selatan dengan menggunakan kaedah Thornthwaite (A spatio-temporal analysis of aridity levels in South Sulawesi using the Thornthwaite method)

Abstract

Kajian ini bertujuan menyelidik dan menganalisis aras kegersangan yang berlaku di seluruh Provinsi Sulawesi Selatan, Indonesia bagi tempoh 10 tahun (1999 – 2008) mengikut masa dan ruang. Data suhu, kerpasan dan sejatpeluhan daripada 66 stesen kajicuaca di seluruh Sulawesi Selatan telah dianalisis. Nilai Indeks Kegersangan kemudiannya dikira dengan menggunakan kaedah imbangan air yang telah dikemukakan oleh Thornthwaite-Mather. Dengan menggunakan Teknik Poligon Thiessen, nilai indeks kegersangan telah diplot mengikut kawasan. Hasil kajian mendapati aras kegersangan di Provinsi Sulawesi Selatan telah diklasifikasikan kepada tiga kelas iaitu indeks kegersangan rendah (< 16.7%) yang meliputi daerah Gowa dan Bone di bahagian Selatan, Luwu Utara dan Luwu Timur di bahagian Utara manakala Pinrang dan Enrekang dibahagian tengah. Sementara itu, indeks kegersangan tinggi (> 33.3%) tersebar pada wilayah Palopo di bahagian utara, Sidrap dan Wajo di bahagian tengah, Makassar, Takalar, Jeneponto, Bulukumba dan Selayar di bahagian selatan manakala daerah lain menunjukkan nilai indeks kegersangan yang sederhana (16.7 – 33.3%). Umumnya, faktor utama berlakunya keadaan kersang di Provinsi Sulawesi Selatan ini adalah curahan hujan yang amat kurang dalam tempoh yang lama dan suhu udara yang berpanjangan tinggi sehingga kadar sejat-peluhan yang tinggi. Dengan keadaan ini menyebabkan banyak kawasan pertanian terutamanya yang bergantung semata-mata kepada air hujan gagal menghasilkan hasil pertanian.

Katakunci: aras kegersangan, curahan hujan, Indeks Kegersangan, kaedah Thornthwaite, teknik Poligon Thiessen, tekstur tanih

This study a spatio-temporal investigation and analysis of the level of aridity for the whole of the South Sulawesi Province, Indonesia for the 10 years period (1999 – 2008). Temperature, precipitation and evapotranspiration data for the 66 meteorological stations throughout the South Sulawesi were analysed by using the water balance technique based on which the aridity index as proposed by Thornthwaite-Mather was then calculated. The calculated values of the aridity indices were then spatially plotted by using the technique of Poligon Thiessen. The results showed that the level of aridity in the SouthSulawesi Province can be classified into three levels i.e., the low level of aridity index (< 16.7%) which was calculated for the districts of Gowa dan Bone in the south, North Luwu ans South Luwu in the north , and Pinrang and Enrekang in the middle region. The high index of aridity (> 33.3%) was calculated for the district of Palopo in the north, Sidrap and Wajo in the middle, and Makassar, Takalar, Jeneponto, Bulukumba and Selayar in the south. Other districts had shown a medium level of aridity index(16.7 – 33.3%). In general, the main factor of the aridity phenomenon in the South Sulawesi Province was the lack of rainfall and the prevalence of high temperatures for a longer period which in turn produced high rates of evapotranspiration. It was observed that in these conditions all agricultural areas which were solely dependent on natural rainfall failed to produce harvests.

Keywords: aridity index, aridity level, Poligon Thiessen technique, rainfall, soil texture, Thornthwaite method