Widayati, Ramadani Masitoh (2020) Pemodelan Numerik Water Balance DAS Cimanuk Sebelum dan Setelah Pengoperasian Waduk Jatigede. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
DAS Cimanuk merupakan salah satu daerah yang memiliki lahan kritis cukup luas. Lahan kritis mengakibatkan DAS Cimanuk menjadi langganan banjir dan kekeringan. Banjir yang terjadi tidak hanya di hilir tetapi juga terjadi di daerah hulu DAS Cimanuk. Penanganan ketersediaan air DAS Cimanuk dilakukan dengan pengaturan air dari Sungai Cimanuk dengan dibangunnya waduk Jatigede. Tujuan dari penelitian ini adalah untuk menilai sumber daya air permukaan yang tersedia di DAS Cimanuk menggunakan simulasi water balance oleh sistem pemodelan hidrologi HEC-HMS berdasarkan kondisi sebelum dan setelah pengoperasiaan waduk Jatigede. Proses hidrologi DAS merupakan hubungan antara masukan berupa hujan, proses, dan keluaran berupa aliran. Proses alihragam hujan menjadi aliran sangat kompleks, dalam menyederhanakannya diperlukan pendekatan model hujan-aliran. Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS) merupakan salah satu model untuk mensimulasikan hujan menjadi aliran. Pemodelan memperkirakan limpasan permukaan dan mensimulasikan proses hidrologi karena penggunaan lahan, jenis tanah, karakteristik DAS, dan meteorologi di DAS. Debit hasil prediksi yang telah di validasi selanjutnya disimulasikan terhadapa pengoperasian waduk Jatigede. Pengoperasian waduk Jatigede dilakukan dengan empat skenario alokasi pemanfaatan air waduk Jatigede. Selanjutnya dilakukan penilaian ketersediaan air permukaan DAS Cimanuk dengan melakukan analisa water balance pada kondisi sebelum dan setelah pengoperasian waduk Jatigede. Hasil penelitian menunjukkan kalibrasi terhadap model menghasilkan nilai NSE 0,64. Sedangkan hasil validasi terbaik pada tahun 2018 dengan NSE 0,575. Hasil simulasi pengoperasian waduk Jatigede dapat mereduksi debit banjir dan memenuhi kebutuhan air untuk air baku 3,5 m3/dt, PLTA 59,63 m3/dt dan sebagian daerah irigasi. Perhitungan kebutuhan air irigasi berdasarkan debit kebutuhan air maksimum untuk tanaman padi pada periode tanam Juni I hingga Juli II. Berdasarkan skenario I dapat mengairi sawah dengan kebutuhan air seluas 55.384,62 ha atau 61,54%; skenario II 52.692,31 ha atau 58,55%; skenario III 9.538,46 ha atau 10,6%; dan skenario IV 6.846,15 ha atau 7,61%. Dilihat dari penilaian water balance, ketersediaan air permukaan sebelum ada waduk hampir terjadi water balance karena debit air yang mengalir di sungai Cimanuk tidak ada pemanfaatan, sehingga inflow sama dengan outflow. Sedangkan setelah pengoperasian waduk Jatigede terjadi selisih antara inflow dan outflow sungai Cimanuk, hal ini dikarenakan adanya pemanfaatan air di waduk. Saat terjadi surplus air, air yang berlebih ini akan tersimpan dalam waduk dan dapat dimanfaatkan untuk kebutuhan saat inflow belum mencukupi kebutuhan. Sedangkan saat terjadi defisit air, kebutuhan lebih besar daripada inflow sehingga debit outflow untuk memenuhi kebutuhan mendapat tambahan dari penyimpanan air di waduk.
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Cimanuk watershed is one of the areas that has quite extensive critical land. Critical land causes Cimanuk watershed to become flood and drought. Floods that occur not ony in the downstream but also occur in the upstream area of Cimanuk watershed. The manajement of Cimanuk watershed water availability is done by regulating water from Cimanuk river with construction of Jatigede reservoir. The purpose of this study was to assess available surface water resources in the Cimanuk watershed using a water balance simulation by HEC-HMS hydrological modeling system based on conditions before and after operation of Jatigede dam. The watershed hydrological is the relationship between inputs in the form of rainfall, processes, and output in the form of streamflow. The process of converting rainfall into runoff is very complex, simplifying the rainfall-runoff model approach is needed. Hydrologic Engineering Center – Hydrologic Modeling System (HEC-HMS) is one model to simulate rainfall into runoff. Modeling estimates surface runoff and simulates hydrological processes due to land use, soil type, watershed characteristics, and meteorology in watersheds. Prediction discharge that has been validated is then simulated on the operation of Jatigede dam. The operation of Jatigede reservoir is carried out with four scenarios for the allocation of water utilization of Jatigede reservoir. Then, assess the availability of surface water in the Cimanuk watershed by analyzing the water balance in the conditions before and after the operation of Jatigede reservoir. The results showed that the calibration of the model produced an NSE value of 0,64. While the best validation results in 2018 with NSE 0,575. The results of the simulation of Jatigede reservoir operation can reduce peak discharge and meet water needs for raw water 3,5 m3/s, hydropower 59,63 m3/s and some irrigation areas. Calculation of irrigation water needs is based on the maximum discharge requirement for rice plants in June I to July II planting period. Based on scenario I, it can irrigation rice fields with a water demand as wide as 55.384,62 ha or 61,54 %; scenario II 52.692,31 ha or 58,55 %; scenario III 9.538,46 ha or 10,6%; and scenario IV 6.846,15 ha or 7,61 %. Seen from the water balance assessment, the availability of surface water before the reservoir is almost done because there is no water balance flowing water in the Cimanuk river, so that inflow is the same as outflow. Meanwhile, after the operation of the Jatigede reservoir, the difference between inflow and outflow of Cimanuk river occurs, this indicates the use of water in the reservoir. When there is a surplus of water, this excess water will be stored in a reservoir and can be used for water needs when water inflow is not sufficient.Whereas when there is a water deficit, the outflow discharge obtain additional from the storage of water in the reservoir.
| Item Type: | Thesis (Masters) |
|---|---|
| Additional Information: | RTS 627.52 Wid p-1 • Widayati, Ramadani Masitoh |
| Uncontrolled Keywords: | Kata Kunci : Water Balance, Surplus dan Defisit Air, Waduk Jatigede, DAS Cimanuk Keywords: Water Balance, Surplus and Deficit Water, Jatigede Reservoir, Cimanuk Watershed. |
| Subjects: | T Technology > TC Hydraulic engineering. Ocean engineering > TC167 Dams, reservoirs T Technology > TC Hydraulic engineering. Ocean engineering > TC424 Water levels T Technology > TC Hydraulic engineering. Ocean engineering > TC812 Irrigation |
| Divisions: | Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22101-(S2) Master Thesis |
| Depositing User: | Ramadani Masitoh Widayati |
| Date Deposited: | 10 Mar 2025 02:21 |
| Last Modified: | 10 Mar 2025 02:21 |
| URI: | http://repository.its.ac.id/id/eprint/76511 |
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