EXPERIMENTAL METHOD 1 Research Area

Bogor, 21-22 October 2015 655 Agroforestry is one of the land use form, consist of a mixture of perennials trees or shrubs with or without crops and livestock in one field. Composition and variation of plants in the agroforestry, provides a function and a role similar to the forest cover more than agriculture, or plantation. Therefore, the agroforestry provides a hydrological function resemble to the forest, especially in maintaining the hydrological functions of watershed Junaidi, 2013. Thus the agroforestry can be applied as an alternative land cover to overcome the deforestation. This study was aimed to compare the watershed hydrological condition affected by 30 forest land cover and 70 agroforestry land cover. 2. EXPERIMENTAL METHOD 2.1 Research Area The research was carried out in the subwatershed of CitanduyHulu, West Java, which lies between Latitude 7 o 7 - 7 o 17 S and Longitude 108 o 4 - 108 o 24 E, with total area approximately 72,409.5 hectares. Figure 1. The main river length is about 7.4 km, with a gradient of 1.02 slight low Puspitodjati etal., 2012. The climate in the watershed categorized slight wet according to classification of Mohr or Schmidt-Ferguson. It has a mean annual precipitation of 2000 mm high criteria in the most of the watershed, and 2000 mm in only about 12 of the watershed area, particularly at the downstream Junaidi Retno, 2013. Figure 1: Research Area 2.2 SWAT Model SWAT model derived from the development of several models namely a model Simulator for Water Resources in Rural Basin SWRRB and is supported by several models, such as Chemicals, Runoff, Erosion from Agricultural Management Systems creams, Groundwater Loading Effects on Agricultural Management Systems gleams and Erosion-Productivity Impact Calculator EPIC Neitsch et al., 2009. SWAT model, is one of the hydrological models that able to simulate the water resources of a watershed, based on changing scenarios desired. SWAT is a mathematical model with physical basis, which is designed as a spatially distributed hydrological model, based on hydrologic response units HRUs, formed from a combination of land use, soil type and topography Omani et al., 2007. SWAT is integrated with GIS and Digital Elevation Model DEM to display a graphical user interface GUI Bogor, 21-22 October 2015 656 Olivera et al., 2006.The operational evaluation based on the daily time scale, and is able to simulate and predict the impact of the activities of long-term land management practices Arnold et al., 2010; Douglas-Mankin et al., 2010. Hydrological processes that simulated by SWAT model are surface flow, lateral flow, evaporation, transpiration, soil water movement and routing flow Menking et al., 2013. There are three types of dataused in the SWAT model in this study: spatial, climate, and hydrological data Table 1. Climate and spatial data is used for input the model, while the hydrology data used for the calibration process and verify the model. Table 1: Spatial, climate and hydrology data in Citanduy Hulu sub watershed No Data types Data source Remark 1. River network map scale 1 : 50.000 Bakosurtanal Peta rupa bumi Indonesia 2. DEM US Geological Survey SRTM Shuttle Radar Topography Mission for Z_59_14.tiff withspatial resolution 90 x 90 m 3. Land use map skala 1 : 250.000 BP DAS Cimanuk – Citanduy Landsat TM, in 2009 4. Soil map scale 1 : 250.000 BP DAS Cimanuk- Citanduy 5. Rain value data Balai Pengelolaan Sumberdaya air Citanduy, Balai Besar wilayah Sungai Citanduy 9 stations of rainfall gauge, recording in 2009 and 2010 6. Temperature data Balai Besar Wilayah Sungai Citanduy 4 stations of temperature, recording in 2009 and 2010 7. Climate data Balai Besar Wilayah Sungai Citanduy 2 stations of climatology rainfall, temperature, wind velocity, and solar radiation intensity recording in 2005 till 2009 8. River flow data Balai Besar Wilayah Sungai Citanduy Station of river gauge at Sindangrasa, in 2009 2.3 Scenarios of land cover changes Scenarios of land cover changes were determined by software Invest 3.2 scenario generator Sharp et al., 2014. There are two main scenarios of land cover changes applied in this research. a. Scenario of 30 of the watershed area is the forest. The land covers that can be converted into forest are land covers with slopes of 35 and within a radius of 2 km of the forest. The main land uses that can be converted into forest are shrubs, gardens and a mixture of dry land agriculture. b. Scenario of 70 of the watershed area is the agroforestry. The land covers that can be converted into agroforestry are land coverswith slopes of 35 and within a radius of 2 km of ariver. The main land uses that cannot be converted into agroforestry are settlements, the body of water, ponds and swamps. Bogor, 21-22 October 2015 657 3. RESULT AND DISCUSSION 3.1 Land cover changes