Analisis Laju Erosi dan Sedimentasi pada DAS Waduk Gongseng untuk Memprediksi Umur Layanan Waduk serta Penanganannya

Auliyah, Khilyatul (2024) Analisis Laju Erosi dan Sedimentasi pada DAS Waduk Gongseng untuk Memprediksi Umur Layanan Waduk serta Penanganannya. Diploma thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Waduk Gongseng yang berlokasi di Desa Kedungsari, Kecamatan Temayang, Kabupaten Bojonegoro. Waduk Gongseng memiliki Daerah Aliran Sungai (DAS) seluas 74,44 km2 dengan inflow utama yaitu Sungai Soko. Pada tahun 2023 Waduk Gongseng mengalami penurunan volume tampungan sebesar 555,97 m3 pada elevasi muka air normal +93.00. Hal tersebut dikarenakan erosi yang terjadi di DAS Waduk Gongseng dan menghasilkan endapan sedimen yang tinggi pada waduk. Sehingga perlu dilakukan analisis laju erosi dan sedimentasi yang terjadi pada DAS Waduk Gongseng untuk dapat memprediksi umur layanan waduk. Analisis laju erosi dan sedimentasi dapat diprediksi dengan menggunakan metode empiris serta bantuan software ArcGIS. Metode empiris tersebut yaitu metode USLE (Universal Soil Loss Equation) dan RUSLE (Revised Universal Soil Loss Equation). Analisis yang dilakukan dengan metode tersebut yaitu analisis faktor erosivitas hujan, faktor erodibilitas tanah, faktor panjang dan kemiringan lereng, serta pengelolaan tanaman dan konservasi tanah. Hasil analisis tersebut digunakan untuk memprediksi besarnya volume sedimentasi pada waduk dengan adanya pengaruh nilai SDR (Sediment Delivery Ratio). Sehingga dari hasil volume sedimentasi tersebut dapat diprediksi umur layanan waduk.
Berdasarkan hasil analisis menggunakan metode USLE dihasilkan laju erosi sebesar 398,041 ton/ha/tahun dan volume sedimentasi sebesar 248.743,25 m3/tahun. Sedangkan dengan metode RUSLE dihasilkan laju erosi sebesar 296,131 ton/ha/tahun dan volume sedimentasi sebesar 185.057,86 m3/tahun. Dari data hasil pengukuran bathimetri didapatkan volume sedimentasi sebesar 277.985,00 m3/tahun. Sehingga dapat disimpulkan bahwa hasil perhitungan dari metode USLE yang dipilih karena hasilnya paling mendekati data pengukuran bathimetri. Kemudian, hasil Metode USLE dilakukan kalibrasi dengan data bathimetri dan mendapatkan hasil volume sedimentasi sebesar 276.082,61 m3/tahun. Dari hasil kalibrasi tersebut diprediksi umur layanan waduk selama 26 tahun. Sehingga perlu dilakukan penanganan secara vegetatif dengan merubah faktor pengelolaan tanaman atau nilai C. jika hal tersebut dilakukan, maka volume sedimentasi akan berkurang menjadi 117.477,53 m3/tahun dan didapatkan hasil penambahan umur layanan waduk selama 61 tahun. Selain itu, diperkirakan lokasi penempatan checkdam sebanyak 5 titik dan lokasi gully plug sebanyak 50 titik pada setiap zona konservasi lahan.
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Gongseng Reservoir is located in Kedungsari Village, Temayang District, Bojonegoro Regency. Gongseng Reservoir has a watershed area of 74.44 km2 with the main inflow being the Soko River. In 2023, Gongseng Reservoir experienced a decrease in storage volume of 555.97 m3 at a normal water level elevation of +93.00. This is due to erosion that occurs in the Gongseng Reservoir watershed and produces high sediment deposits in the reservoir. So it is necessary to analyze the rate of erosion and sedimentation that occurs in the Gongseng Reservoir watershed to be able to predict the service life of the reservoir. Erosion and sedimentation rate analysis can be predicted using empirical methods and ArcGIS software. The empirical methods are the USLE (Universal Soil Loss Equation) and RUSLE (Revised Universal Soil Loss Equation) methods. The analysis carried out with these methods is the analysis of rain erosivity factors, soil erodibility factors, slope length and slope factors, as well as crop management and soil conservation. The results of the analysis are used to predict the amount of sedimentation volume in the reservoir with the influence of the SDR (Sediment Delivery Ratio) value. So that from the results of the sedimentation volume, the service life of the reservoir can be predicted. Based on the results of the analysis using the USLE method, the erosion rate was 398.041 tons/ha/year and the sedimentation volume was 248,743.25 m3/year. Meanwhile, the RUSLE method resulted in an erosion rate of 296.131 tons/ha/year and a sedimentation volume of 185,057.86 m3/year. From the bathymetry measurement data, the sedimentation volume is 277,985.00 m3 / year. So it can be concluded that the calculation results from the USLE method were chosen because the results are closest to the bathymetry measurement data. Then, the results of the USLE Method were calibrated with bathymetry data and obtained a sedimentation volume of 276,082.61 m3 / year. From the calibration results, it is predicted that the service life of the reservoir will be 26 years. So it is necessary to do vegetative handling by changing the plant management factor or C value. If this is done, the sedimentation volume will be reduced to 117,477.53 m3 /year and the result is an additional 61 years of reservoir service life. In addition, it is estimated that the checkdam placement location is 5 points and the gully plug location is 50 points in each land conservation zone.

Item Type:	Thesis (Diploma)
Uncontrolled Keywords:	Erosion, Sedimentation, USLE, RUSLE, Gongseng Reservoir Watershed, Erosi, Sedimentasi, DAS Waduk Gongseng
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC175.2 Sediment transport
Divisions:	Faculty of Vocational > Civil Infrastructure Engineering (D4)
Depositing User:	KHILYATUL AULIYAH
Date Deposited:	15 Aug 2024 08:21
Last Modified:	15 Aug 2024 08:21
URI:	http://repository.its.ac.id/id/eprint/112678

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