Judul: Prediksi Aliran Permukaan pada DAS Mikro Bungku dan DAS Batang Tabir, Provinsi Jambi Menggunakan Model SCS-CN.
Abstrak: The interaction between human and biophysical condition, which include making changes and regulating landuse in order to fulfil their needs can nevertheless destruct the hydrological function of watershed. A Good hydrological function achieved if there is an equilibrium water system to prevent the water shortages in the dry season or water excess in the rainy season. The analysis of the water system is required to determine the impact of the landuse changes. Therefore, it is necessary to conduct a simulation process that makes the water system in a watershed can be learned in a more simple way. The simulation and simplification process is developed in various models. The use of the model certainly has its own limitations and advantages due to the data availability. One of the models used to predict the overland flow in a watershed is a Soil Conservation Service model - Curve Number (SCS-CN). This is a rainfall-runoff model developed by United States Department of Agriculture (USDA), using rainfall data, soil texture, vegetation, initial abstraction as the input and overland flow as the output. Thus, this research aims at: (1) Assessing the biophysical and hydrological characteristics of land in Bungku micro watershed and Batang Tabir watershed, and 2) Predicting the overland Low data by using the Soil Conservation Service - Curve Number (SCS-CN). The study was conducted in two different watershed areas, namely in Bungku micro watershed with 14.02 hectare square, located in Bungku the Village, Bajubang sub District, Batanghari district, and in Batang Tabir watershed with an area of 107 442.86 hectares square located in Merangin, Bungo and Kerinci district. Data collection was conducted from January 2013 as the primary gathered in Bungku micro watershed November 2013 - January 2014, while in Batang Tabir watershed was held in February - March 2014. The result of this research showed that Bungku micro watershed has a hilly and valley terrain conditions characterized by the dominant slope which is a steep slope with a landcover an area consisting of 1.16 hectare square forest and oil palm plantations with a different undercover vegetation, such as coarse grass (2.09 hectare square), shrubs (7.12 hectare square), and bare land (3.65 hectare square). The Distribution of soil texture in this location is quite varied with clay loam (46%) as dominant texture, followed by loam (24%), and clay (21%). Based on the type of soil texture and infiltration that occurs in this area, the dominant hydrologic soil group (HSG) in Bungku micro watershed is group D with the average value of Antecedant Moisture Condition (AMC) which is in the condition I during field observation and having CN varies between grades 73-88. The highest daily rainfall is 64.34 mm while the lowest si 1.95 mm. The result of the highest prediction overland flow of the model is on December 6th, 2013 in 43.11 mm by 58.49 mm rainfall while the lowest is on December 5th, 2013, as high as 0.12 mm with 4.55 mm rainfall. Batang Tabir watershed exhibits various type of landuse compared with Bungku micro watershed, ie forest (67.81%), Mixed Garden (5.16%), oil palm plantation
Keyword: landuse, SCS-CN model, overland flow