Penilaian Kesehatan Daerah Aliran Sungai (DAS) Bedog Ditinjau dari Faktor Hidrologi Menggunakan Model Mock

Muhammad Shafa Aldith Ariela, Hanggar Ganara Mawandha, S.T., M.Eng., Ph.D. ; Chandra Setyawan, STP., M.Eng., Ph.D, IPM., ASEAN Eng., APEC Eng

2026 | Skripsi | TEKNIK PERTANIAN

Kesehatan Daerah Aliran Sungai (DAS) mencerminkan keseimbangan antara faktor hidrologi, kondisi lahan-biofisik, dan sosial-ekonomi, yang di DAS Bedog berpotensi terganggu oleh perubahan penggunaan lahan yang pesat. Penelitian ini bertujuan menilai status kesehatan DAS Bedog ditinjau dari faktor hidrologi melalui kalibrasi dan aplikasi Model Mock.

Penelitian dilakukan melalui kalibrasi parameter Model Mock menggunakan data curah hujan, klimatologi, dan debit sungai tengah-bulanan tahun 2015–2020, dilanjutkan simulasi debit sungai tahun 2021–2023 untuk menghitung Koefisien Rejim Aliran (KRA), Koefisien Aliran Tahunan (KAT), dan indeks simpanan air (ISA) yang dinilai berdasarkan konstanta resesi air tanah (K) dan tampungan air tanah atau Groundwater Storage (GWS). Kalibrasi menghasilkan koefisien korelasi (R) = 0,876, volume error 5,00%, dan K = 0,995. Hasil simulasi menunjukkan Direct Runoff 882,62 mm (71,56%) dan Baseflow 350,82 mm (28,44%) dari total limpasan 1.233,43 mm selama 2021–2023, setara volume limpasan tahunan rerata sekitar 62,31 juta m3. Nilai KRA berkisar 7,88–14,35 dan KAT 0,164–0,199 (keduanya tergolong sangat rendah), sedangkan GWS sebesar 809–1.074 mm responsif terhadap variabilitas hujan antartahun.

Secara komposit, ketiga indikator hidrologi tersebut menunjukkan status kesehatan DAS Bedog periode 2021–2023 tergolong baik, dengan skor rerata 5 (dari rentang 1–5). Namun, penilaian ini hanya mencerminkan faktor hidrologi, dan tekanan alih fungsi lahan di kawasan hulu-tengah DAS berpotensi mengancam keberlanjutannya tanpa upaya konservasi tanah dan air yang memadai.

Watershed health reflects the balance among hydrological, land-biophysical, and socio-economic factors, which in the Bedog Watershed may be disrupted by rapid land-use change. This study aimed to assess the health status of the Bedog Watershed in terms of hydrological factors through the calibration and application of the Mock Model.

The Mock Model was calibrated using rainfall, climatological, and semi-monthly river discharge data for 2015–2020, followed by river discharge simulation for 2021–2023 to calculate the Flow Regime Coefficient (FRC), Annual Flow Coefficient (AFC), and Water Storage Index (WSI), which was assessed based on the groundwater recession constant (K) and groundwater storage (GWS). Calibration yielded a correlation coefficient (R) of 0.876, a volume error of 5.00%, and K of 0.995. The simulation showed a direct runoff of 882.62 mm (71.56%) and a baseflow of 350.82 mm (28.44%) out of the total runoff of 1,233.43 mm over 2021–2023, equivalent to a mean annual runoff volume of about 62.31 million m3. FRC ranged from 7.88 to 14.35 and AFC from 0.164 to 0.199 (both classified as very low), while GWS (809–1,074 mm) responded to interannual rainfall variability.

Collectively, these three indicators show that the health status of the Bedog Watershed during 2021–2023 was in the good category, with a mean score of 5 (on a scale of 1–5). However, this assessment reflects hydrological factors only, and land-use conversion pressure in the upper-middle watershed may threaten its sustainability without adequate soil and water conservation efforts.

Kata Kunci : DAS Bedog, kesehatan DAS, hidrologi, Model Mock, Koefisien Rejim Aliran, Koefisien Aliran Tahunan, Indeks Simpanan Air