Kajian kualitas air Sungai Code Daerah Istimewa Yogyakarta atas dasar perbedaan penggunaan lahan

MUNAWAR, Masud, Dr. Igl. Setyawan Purnama, M.Si

2010 | Tesis | S2 Ilmu Lingkungan

Penelitian ini dilakukan di DAS Code Propinsi DIY, dilatarbelakangi oleh perkembangan Kota Yogyakarta yang memiliki kecenderungan perubahan penggunaan lahan dari lahan non permukiman menjadi lahan permukiman. Pengaruh perubahan lahan permukiman yang meningkat terhadap kondisi aliran sungai, salah satunya limbah domestik, dimana sebagian besar masyarakat mengalirkan ke tubuh sungai. kondisi ini diperparah dengan industri-industri di sempadan sungai juga membuang limbah ke tubuh sungai sehingga berdampak kepada kualitas air. Adanya masukan bahan-bahan terlarut yang dihasilkan oleh kegiatan penduduk di DAS Code sampai batas tertentu tidak akan menurunkan kualitas air sungai. Oleh karena itu, penelitian ini bertujuan untuk (1) Mengetahui kondisi kualitas air Sungai Code dengan adanya variasi pengunaan lahan yang berbeda, (2) Mengetahui proses pemurnian diri (self purification) di Sungai Code, dan (3) Mengetahui nilai ekonomi yang ditimbulkan akibat pencemaran air di Sungai Code. Metode penelitian yang digunakan adalah metode survei data primer dan data sekunder. Pengambilan sampel air menggunakan metode Purposive Sampling dengan pembagian lokasi atas tiga yaitu bagian hulu, tengah, dan hilir, dimana masing-masing lokasi (hulu, tengah, hilir) yang diperkirakan ada pengaruh dari penggunaan lahan yang berbeda. Analisis laboratorium parameter kualitas air dilakukan secara plotting grafik, analisis spasial dengan perbedaan penggunaan lahan dan analisis swa-penahiran serta analisis ekonomi kemampuan membayar masyarakat (willingness to pay) terhadap preferensi barang lingkungan yang tercemar. Hasil penelitian menunjukkan bahwa kondisi kualitas air Sungai Code berdasarkan sifat fisik, baik itu di bagian hulu, tengah maupun hilir masih terlihat baik. Namun dilihat dari sifat kimia dan biologi ada beberapa parameter yang telah melebihi baku mutu terutama pada wilayah Sungai Code bagian tengah. Hal ini wajar terjadi karena pada Sungai Code bagian tengah didominasi oleh penggunaan lahan permukiman dan masyarakat yang berdomisili disekitar Sungai Code langsung membuang limbah rumah tangga mereka ke sungai tanpa melalui saluran pembuangan air limbah. Proses pemurnian diri yang terjadi di Sungai Code terlihat jelas dengan semakin turunnya kandungan BOD ketika telah melewati Sungai Code bagian tengah, hal ini terjadi sebagai akibat adanya reoksigenasi dan turbulensi aliran sungai serta tidak ada penambahan air limbah ketika berlangsungnya proses swa penahiran. Berdasarkan hasil perhitungan diperoleh nilai dugaan rataan WTP (EWTP) sebesar Rp. 361.333,- akibat timbulnya pencemaran air Sungai Code .

This research was conducted in the river catchment area of Code River at DIY Province as a response to the trends of changes in land use in Yogyakarta city development that shifted non-residential land to residential land. This increasing change into residential land has influenced river flow condition, e.g. domestic waste which threw into river body by the most of citizen member. This situation is aggravated by industrial waste from industries located around the river that affect water quality. The inputs of dissolved materials, which generated by population who lives in Code river catchment area, to a certain extent would not decline the quality of river water. Therefore, this study aims to (1) determine the quality of water at Code River with land use differences, (2) determine the selfpurification process in Code River, and (3) measuring economic value that resulted from water pollution in Code River. Methods used in this research are survey method of primary and secondary data. Water sampling was using purposive sampling method which located at three divisions of river location namely the upstream, middle, and downstream, where each location (upstream, middle, downstream) were assumed to be influenced by land use differences. Laboratory analysis on water quality parameters was done by graphic plotting, spatial analysis by land use differences and self-purification, and economic analysis of community’s willingness to pay contaminated environmental goods preferences. The results showed that, based on its physical properties, the quality of water in Code River in the upstream, middle and downstream is still looks good. Based on its chemical and biological properties, however, there are several parameters that have exceeded the quality standards, especially in the middle area of Code River. This is reasonable because the middle area of Code River is dominated by residential land use and the community who lives around the River Code discards their household waste directly into the river without going through the waste water drain. Self-purification processes that occur in the River Code were apparent with the decrease of BOD content when the water has passed through the middle area. This is a result of water reoxygenation and turbulence and no additional waste water when the self-purification process occurred. Based on calculations, EWTP values derived of Rp. 361,333, - due to the emergence of water pollution in Code River.

Kata Kunci : Kualitas air,Variasi penggunaan lahan,Swa penahiran,WTP, water quality, land use different, self-purification