KUALITAS FISIK, KIMIA, DAN BIOLOGIK PADA EKOSISTEM SUNGAI GAJAHWONG DAS OPAK PROVINSI DAERAH ISTIMEWA YOGYAKARTA

INDRA HARI PRATAMA, Erny Poedjirahajoe

2010 | Skripsi | S1 KEHUTANAN

Meningkatnya jumlah penduduk dan pembangunan ekonomi menyebabkan semakin meningkatnya tekanan terhadap lahan. Hutan semakin lama semakin berkurang karena berubah fungsi menjadi daerah permukiman, industri, dan pertanian. Hal tersebut menyebabkan fungsi hidroorologi ekosistem hutan tidak berjalan sebagaimana mestinya, sehingga kualitas DAS pun turut mengalami penurunan. Oleh karena itu perlu ada pengkajian mengenai kualitas ekosistem perairan DAS secara berkelanjutan dan melibatkan berbagai pihak. Penelitian dengan judul Kualitas Fisik, Kimia, dan Biologik pada Ekosistem Sungai Gajahwong DAS Opak Provinsi Daerah Istimewa Yogyakarta berlokasi di dua kabupaten di DIY, yaitu Sleman dan Bantul dan satu kota Yogyakarta mempunyai dua tujuan. Tujuan yang pertama adalah untuk mengetahui kualitas ekosistem perairan Sungai Gajahwong berdasarkan parameter fisik, kimia, dan biologik. Tujuan yang kedua adalah untuk mengetahui perbedaan kualitas ekosistem perairan hulu, tengah, dan hilir Sungai Gajahwong berdasarkan parameter fisik, kimia, dan biologik. Pengambilan data dilakukan pada 2 plot di hulu, 3 di tengah dan 2 hilir Sungai Gajahwong. Hasil penelitian menunjukkan bahwa rata-rata suhu hulu sebesar 25,53 oC, tengah sebesar 27,45 oC, hilir sebesar 29,1 oC; kecepatan arus hulu 92,11 m/det, tengah 35,94 m/det, hilir 18,72 m/det; tingkat kejernihan hulu 8,72 cm, tengah 6,06 cm, hilir 7,28 cm; pH hulu 6,17, tengah 5,83, hilir 6,5; DO hulu 10,67 ppm, tengah 9,28 ppm, hilir 10,87 ppm; kadar amonia hulu 8,32 ppm, tengah 5,20 ppm, hilir 6,02 ppm; kadar sulfida hulu 26,96 ppm, tengah 24,39 ppm, hilir 26,48 ppm; keragaman plankton hulu 0,95, tengah 0,93, hilir 0,94; kepadatan plankton hulu 3,47 individu/ml, tengah 1,61 individu/ml, hilir 2,72 individu/ml. Dari hasil perhitungan di atas menunjukkan bahwa terjadi penurunan kualitas perairan Sungai Gajahwong pada bagian tengah, kemudian meningkat lagi di bagian hilir. Penurunan kualitas pada bagian tengah disebabkan oleh perilaku membuang sampah ke sungai oleh masyarakat sekitar. Perlu adanya upaya pengawasan terhadap kualitas air di Sungai Gajahwong yang melibatkan pemerintah, pihakpihak terkait, dan juga masyarakat sekitar Sungai Gajahwong.

The population increasement and economic establishment cause the increase of field pressure. Forest area are getting less because of land convertion to housing, industrial, dan farming. Those land convertion cause the hidroorology function of forest ecosystem does not work as ussual, therefor the watershed quality are going less. In that case need a research in watershed ecosystem quality which continuity and involving related stakeholders. The Physical, Chemical, and Biological Qualities of Gajahwong River Ecosystem Opak Watershed in the Yogyakarta Special Province research that took place in two regencies, Sleman and Bantul and one city, Yogyakarta had two purposes. The first purpose was to find out the quality of the Gajahwong River ecosystem based on physical, chemical, and biological parameters. The second purpose was to find out the difference between high land, middle land, and low land water ecosystems based on physical, chemical, and biological parameters. The data atained took place on two plots in high land, three in middle land, and two in low land in the Gajahwong River. The result of this research showed that the temperature average in high land was 25,53 oC, middle land was 27,45 oC, low land was 29,1 oC; velocity/flow rate in high land was 92,11 m/s, middle land was 35,94 m/s, low land was 18,72 m/s; water purity in high land was 8,72 cm, middle land was 6,06 cm, low land was 7,28 cm; pH in high land was 6,17, middle land was 5,83, low land 6,5; DO in high land was 10,67 ppm, middle land 9,28 ppm, low land was 10,87 ppm; amonia contents in high land was 8,32 ppm, middle land was 5,20 ppm, low land was 6,02 ppm; sulfida contents in high land was 26,96 ppm, middle land was 24,39 ppm, low land was 26,48 ppm; plankton index diversity in high land was 0,95, middle land was 0,93, low land was 0,94; plankton density in high land was 3,47 individu/ml, middle land was 1,61 individu/ml, low land was 2,72 individu/ml. Based on that result above, we can conclude that there is a reduction of in the quality of the Gajahwong River on the middle land water ecosystem, then increases on the low land water ecosystem. The reduction is caused by the nearby people throwing trash into the river. It is necessary to control the quality of the Gajahwong River ecosystem quality that involves the government, the related stakeholders, and the community that surrounds the Gajahwong River.

Kata Kunci : Kualitas perairan, Sungai Gajahwong, Parameter fisik, kimia, dan biologik