PENGEMBANGAN METODE PENETAPAN STATUS KESEHATAN PERAIRAN SUNGAI DI DAERAH TROPIS BERBASIS EKOHIDRAULIK

SRI PUJI SARASWATI, Prof. Dr. Ir. Sunjoto, Dip.HE., DEA.

2015 | Disertasi | S3 Ilmu Teknik Sipil

Degradasi ekosistem sungai terjadi antara lain karena pengelolaannya masih menggunakan pendekatan parsial dan multi-disipliner belum secara ekohidraulik yang pendekatannya komprehensif dan interdisipliner. Pada umumnya penetapan status kualitas air didasarkan pada target peruntukan spesifik seperti air minum, pertanian dsb, sementara penetapan kesehatan perairan sungai membutuhkan pendekatan yang multi fungsi. Penelitian ini bermaksud mengembangkan metode penetapan kesehatan perairan sungai di Indonesia secara komprehensif yang penggunaan airnya bersifat multi fungsi. Metode ini didasarkan pada uji toksisitas air ex-situ dengan memodifikasi metode AOD (Aquatic Organisms Environmental Diagnostic) dan pengembangan indeks kualitas air komprehensif berbasis analisa multi parameter kualitas air ex-situ. Metode yang dikembangkan dinamakan sebagai metode AODs (Aquatic Organisme Environmental Diagnostic, sungai) dan IKAs (Indeks Kualitas Air sungai). Metode IKAs dihasilkan melalui kajian beberapa rumus IKA yang telah berkembang dengan menggunakan data sekunder kualitas air di Yogyakarta selama 16 tahun (April 1997 – Desember 2011). Pengembangan metode IKAs mempertimbangkan keberagaman kondisi perairan Indonesia dan integrasi kriteria ekologi dalam teknik transformasi/standarisasi data untuk Analisis Komponen Utama dan Analisis Faktor. Sementara metode baku AODs dikembangkan dengan memodifikasi metode AOD menggunakan hewan uji lokal yang kosmopolitan di seluruh wilayah Indonesia, merubah suhu bioassay, memperpanjang rentang skala pengujian dengan pengenceran sampel, serta pengembangan metode standar aklimatisasi hewan uji. Metode IKAs dan AODs selanjutnya diaplikasikan di 5 titik sampel air pada sungai yang sama, dan dikon-firmasi dengan hasil mutu air menurut biotilik makrobenthos yang terpapar polusi secara langsung di sungai. Penelitian ini menghasilkan sebuah formula indeks kualitas air untuk sungai Gadjah Wong yaitu IKAs = 0,20ECt + 0,15CODt + 0,21DOt + 0,20NH3Nt + 0,10TCt; dengan 2 kelas mutu air sungai yaitu kelas tercemar, skor negatif (< 0) dan kelas tidak tercemar, skor positif (> 0) sementara skor 0 adalah ambang batas konsentrasi konservasi kualitas air sungai. Selain itu dihasilkan tolok ukur konservasi kualitas air Gadjah Wong, teknik transformasi/standarisasi data kualitas air dan protokol penyusunan metode IKAs bagi sungai lain di Indonesia, serta protokol uji toksisitas AODs untuk sungai tropis di Indonesia. Kelas mutu air sungai Gadjah Wong di bagian hulu hingga tengah sungai, tidak tercemar jika 48h-LC50 AODs ≥ 620% yang setara dengan tolok ukur EC ≤ 300 μS/cm. Hasil uji konfirmasi menunjukkan bahwa metode IKAs dan AODs mempunyai korelasi kuat dengan biotilik makrobenthos in-situ. Dengan demikian IKAs dan AODs merupakan IKA komprehensif yang memadukan pendekatan penilaian mutu air secara ex-situ dan in-situ, sekaligus mencerminkan kondisi ekogeografi setempat. IKAs akan memudahkan praktisi dalam mengelola sungai (in-stream dan off stream control) karena dapat dihubungkan dengan strategi operasional manajemen sungai yang ekologis serta berkelanjutan. IKAs dapat diperoleh dari pemantauan kualitas air dengan data dari satu kali pemantauan (single sampling) serta dapat pula diterapkan di banyak lokasi pantau dalam wilayah luas secara periodik atau jangka panjang. Gabungan metode tersebut diharapkan akan berguna bagi pengelolaan sungai dan mampu mengatasi masalah degradasi ekosistem sungai dan menghindari terjadinya bencana ekologi sungai-sungai di Indonesia.

River ecosystem degradation occurs, among others due to river management that is still based on a partial and multi-disciplinary approach, it has not been conducted with eco-hydraulics concept that is more comprehensive and interdisciplinary approach. Most of the current practice to determine water quality status is based on specific usage target, while by nature river health is more general water usage or multi function. This research intends to develop a method of comprehensive water quality index that is multifunction to measure river health in Indonesia. This method is based on ex-situ aquatic toxicity test by modifying the method of AOD (Aquatic Organisms Environmental Diagnostics), and the development of a water quality index based on ex-situ water quality multi-parameters. The method developed is called AODs (Aquatic Organisms Environmental Diagnostic, sungai) and IKAs (Indeks Kualitas Air, sungai). IKAs method was developed through a study of some existing IKA formulas with secondary data from PROKASIH water quality measurement (Clean River Program) in Yogyakarta for 16 years (April 1997 - December 2011). In the development of IKAs method, the diversity of Indonesian river water conditions were taken into consideration in the integration of ecological criteria in the standardization technique using Principal Component Analysis and Factor Analysis. While in the standardization of the laboratory test procedures for AODs by modification of original AOD using test animals which are cosmopolitan for the entire regions of Indonesia, modifying bioassay temperature, extending the measurement scale by dilution of sample, and developing a standardized acclimatization procedure of test animals. IKAs and AODs method was then applied at 5 points of water samples in the same river, and confirmed by the results of water quality measurement method based on macrobenthos biomonitoring directly exposed to pollution in the river. The research resulted in IKAs formula for Gadjah Wong river i.e IKAs = 0,20ECt + 0,15CODt + 0,21DOt + 0,20NH3Nt + 0,10TCt; with 2 class scores i.e polluted/bad which score negative (<0) and non polluted/good which score positive (>0) whereas score 0 is the reference concentration for water quality conservation. In addition, this research has produced water conservation quality standard, a technique of transformation/standardization of water quality data and a protocol for IKAs method development for other rivers in Indonesia; also AODs toxicity test protocols for tropical rivers in Indonesia. Good river water quality class for Gadjah Wong river at up to midstream is given by 48h-LC50 AODs ≥ 620% or equal to EC concentration of 300 μS/cm. Result from confirmation test showed that IKAs and AODs methods have a strong correlation with in-situ macrobenthic biomonitoring results. This finding confirms that IKAs and AODs methods is a comprehensive IKA that can describe the holistic river water health, combining approaches of ex-situ and in-situ water quality assessment, reflecting local eco-geographical conditions. IKAs will allow practitioners to manage the river (in-stream and off stream control) because it can be connected to the operational strategy of the river management for ecological and sustainable development. IKAs can be obtained from the water quality monitoring data with a single sampling and can also be applied for many monitoring locations in a broad region, periodically or long-term monitoring. The combined methods are expected to be useful for river management program that is able to prevent the river ecosystem degradation and to avoid ecological river disasters in Indonesia.

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