Suryoputro, Nugroho and Prof. Dr. Ir. Suhardjono,, M.Pd., Dipl.HE. and Dr. Ir. Widandi Soetopo,, M.Eng. and Dr. Ery Suhartanto,, ST., M.T. (2018) Pengembangan Model Tangki akibat Pengaruh Intersepsi dan Penyerapan Air Tanah oleh Akar Tanaman. Doktor thesis, Universitas Brawijaya.
Abstract
Model tangki Sugawara adalah salah satu model hujan-limpasan yang banyak digunakan dan dikembangkan oleh para ahli hidrologi sejak pertama kali diperkenalkan oleh Sugawara dan Funiyuki tahun 1956. Permasalahan dalam model tangki adalah: kurang akuratnya debit hasil simulasi yang disebabkan kurang lengkapnya proses pemodelan intersepsi dan penyerapan air tanah oleh akar tanaman (water uptake). Tujuan penelitian ini adalah mengembangkan model tangki dengan memasukkan intersepsi dan penyerapan air tanah oleh akar tanaman berdasarkan tata guna lahan. Penelitian dilaksanakan di Wilayah Brantas Hulu. Empat sub DAS diambil dalam penelitian. Tiga sub DAS dengan alat ukur manual harian meliputi DAS dengan persentase hutan lebih kecil ±30% (sub DAS Bango), antara ±30 - ±60% (sub DAS Brantas Hulu), dan di atas ±60% (sub DAS Coban Rondo). Satu sub DAS dengan data alat ukur otomatis jam-jaman diambil yaitu sub DAS AWLR Gadang. 42 sampel tanah diambil berdasarkan jenis tanah dan diukur infiltrasinya dengan Turf-Tech Infiltrometer. Pengujian karakteristik tanah meliputi berat jenis, berat isi, porositas, kadar air dan tekstur tanah dilaksanakan di laboratorium Fisika Tanah, Fakultas Pertanian Universitas Brawijaya. Pengembangan model tangki meliputi koefisien infiltrasi riil, model intersepsi dan penyerapan air tanah oleh akar tanaman berdasarkan tata guna lahan, struktur model dan lebar data input-output, dan model optimasi hybrid gabungan Random Search dan Genetic algorithm. Hasil penelitian menunjukkan: 1) tekstur tanah pada lokasi DAS penelitian didominasi debu dan pasir dengan laju infiltrasi masuk kategori cepat (laju infiltrasi akhir pengukuran (fc) rata-rata = 3,55 mm/menit > 0,42 mm/menit), model infiltrasi yang sesuai adalah Horton (nilai Nash = 0,64); 2) struktur model tangki terbaik terdiri dari 4 tangki yang tersusun secara seri dengan nilai Nash = 0,81 dimana nilai model terbaik jika nilai Nash mendekati 1,0; 3) model memberikan hasil kinerja terbaik untuk simulasi bulanan (nilai Nash = 0,97) ; 4) persamaan matematika model tangki hasil pengembangan adalah fungsi dari hujan, evapotranspirasi, koefisien debit lubang pengeluaran, tinggi lubang tangki, persentase luas tata guna lahan, intersepsi tajuk, koefisien tanaman, koefisien penyerapan air tanah oleh akar tanaman (CUptake), infiltrasi riil, tinggi limpasan sungai; 5) hasil uji statistik dengan Paired Sampel t-Test (diuji pada α = 5%) antara model sebelum dimodifikasi dan setelah dimodifikasi menunjukkan perubahan signifikan (t hitung = 9,23 > t kritis = 1,98). Hasil analisis menunjukkan semakin besar persentase hutan dan kebun, maka semakin besar pengaruh intersepsi dan penyerapan air oleh akar tanaman dalam pemodelan.
English Abstract
The Sugawara tank model is a conceptual rainfall-runoff model extensively used and developed by hydrologists after being pioneered by Sugawara and Funiyuki in 1956. The drawbacks to the tank model are less accurate simulated discharge, less complete modelling process including interception and root uptake. This research aimed to develop the tank model with interception and root uptake based on land use. The research was conducted in the upper reaches of the Brantas watershed. Four sub-watersheds were included in this study. Three sub-watersheds equipped with daily manual gauges were examined, namely Bango sub-watershed (± 30% forest cover), Brantas upper watershed (± 30-60% forest cover) and Coban Rondo sub-watershed (above ± 60% forest cover). The last area, Gadang sub-watershed, was studied by analysing the data from the Automatic Water Level Recorder (AWLR). 42 soil samples were taken based on soil types. Turf-Tec Infiltrometer was used to measure the infiltration rates. Tests of soil properties including specific gravity, bulk density, porosity, water content and soil texture were performed at the Laboratory of Soil Physics, Faculty of Agriculture, Universitas Brawijaya. The development of tank model involved the coefficients of actual infiltration, interception and root uptake based on land use, model structure and input-output data, and a hybrid optimisation method of random search and genetic algorithm. The results of the study are summarised as follows. 1) The soil texture at the watersheds under study was dominated by dust and sand with infiltration rates categorised as fast (average final infiltration rate (fc) = 3.55 mm/min > 0.42 mm/min); the Horton infiltration model was considered the most suitable (Nash value = 0.64). 2) The best structure of the tank model was composed of four tanks arranged in series (Nash value = 0.81). 3) The best input-output data length was monthly (Nash value = 0.97). 4) The mathematical equation of the developed tank model was a function of rainfall, evapotranspiration, outlet flow coefficient, outlet height, percentage of land use area, canopy interception, crop coefficient, root uptake coefficient (CUptake), actual infiltration, river runoff height. 5) The results of the paired samples t-test (tested at α = 5%) between models with and without modifications showed a significant change (t Stat = 9.23 > t Critical = 1.98). The analysis results suggested that the greater the percentage of forest and plantation area, the greater the influence of interception and root uptake in the modelling process.
| Item Type: | Thesis (Doktor) |
|---|---|
| Identification Number: | DIS/575.76/SUR/p/2018/061809858 |
| Uncontrolled Keywords: | model tangki, intersepsi, penyerapan air, akar tanaman,tank model, interception, water uptake, plant root |
| Subjects: | 500 Natural sciences and mathematics > 575 Specific parts of and physiological systems in plants |
| Divisions: | S2/S3 > Doktor Teknik Sipil, Fakultas Teknik |
| Depositing User: | soegeng sugeng |
| Date Deposited: | 17 Oct 2022 02:28 |
| Last Modified: | 17 Oct 2022 02:28 |
| URI: | http://repository.ub.ac.id/id/eprint/195723 |
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