EVALUASI KINERJA MODEL HUJAN ALIRAN LUMPED DALAM PENENTUAN ALIRAN DASAR DI DAERAH ALIRAN SUNGAI CITARUM

Brigita Diaz Primadita, M. Syahril Badri Kusuma, Waluyo Hatmoko

Abstract


ABSTRACT

Studies related to baseflow modeling are still rarely carried out compared to flood modeling. The commonly used rainfall-runoff models oversimplify the baseflow process, which leads to poor low-flow simulations. Baseflow plays an important role in regulating the seasonal distribution of river flow, maintaining aquatic habitats, and transporting chemical nutrients in the river system. If the baseflow decreases in the Citarum Watershed, there will be consequential impacts on the Java-Bali electricity supply, rice field irrigation water, raw water, and industrial water in West Java and DKI Jakarta. This study evaluates six lumped-rainfall-runoff models that are popularly used in the Ministry of Public Works and Housing of Indonesia, namely Mock, NRECA, HBV96, NAM, Sacramento, and Empirical to simulate baseflow on the Nanjung Subwatershed and Cisokan Subwatershed. The baseflow simulations from each model are compared with the observational baseflow. The observational baseflow is obtained using the Recursive Digital Filter Lyne and Holick one filter methods. To quantify model comparison, a multi-criteria matrix is used consisting of the model convenience, baseflow parameters, and model performance. This study shows that the Mock Model gives the best results with a "Satisfactory" score for simulating baseflow in NSE and RMSE values, the Q50-Q80 differences, and the difference in flow heights compared to the other five models. In addition, the Mock Model is also relatively easy, accessible, and familiar to use.

Keywords:      Baseflow, Rainfall-Runoff, Lumped, Citarum, Recursive Digital Filter

ABSTRAK

Kajian terkait pemodelan aliran dasar masih jarang dilakukan dibandingkan pemodelan banjir. Model hujan-aliran yang umumnya digunakan mengasumsikan perhitungan aliran dasar secara sederhana sehingga menghasilkan simulasi aliran rendah yang buruk. Padahal penentuan aliran dasar sangat diperlukan mengingat pentingnya fungsi aliran dasar dalam mengatur distribusi musiman aliran sungai, mempertahankan habitat air, dan mengangkut nutrisi-bahan kimia dalam sistem sungai. Apabila terjadi penurunan aliran dasar di Daerah Aliran Sungai (DAS) Citarum maka dampaknya akan signifikan pada pasokan listrik Jawa-Bali, air irigasi sawah, air baku, dan air industri di Jawa Barat dan DKI Jakarta. Penelitian ini mengevaluasi enam model hujan-aliran lumped yang populer digunakan di Kementerian PUPR, yaitu Mock, NRECA, HBV96, NAM, Sacramento, dan Empiris untuk menentukan besarnya aliran dasar pada Sub-DAS Nanjung dan Sub-DAS Cisokan. Hasil pemodelan kemudian dibandingkan dengan hasil pemisahan aliran dasar dari debit observasi yang diperoleh melalui Metode Recursive Digital Filter Lyne dan Holick satu filter. Untuk memudahkan perbandingan model, digunakan matriks multi-kriteria dengan parameter pembanding kemudahan pemodelan, ada tidaknya parameter aliran dasar, dan kinerja model. Penelitian menunjukkan Model Mock memberikan hasil paling baik dengan skor “Memuaskan” untuk mensimulasikan aliran dasar di lokasi kajian berdasarkan nilai NSE dan RMSE, selisih Q50-Q80, dan selisih tinggi aliran dibandingkan kelima model lain. Selain itu, Model Mock juga relatif mudah, aksesibel, dan familiar untuk menentukan aliran dasar di lokasi kajian.

Kata Kunci: Aliran dasar, Hujan-Aliran, Lumped, Citarum, Recursive Digital Filter 


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DOI: https://doi.org/10.32679/jth.v14i2.735

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