Description

Summary: Based on Proposal #9 of TMPEGS-Indonesia Year-3 (Y-3) Work Plan, the target in this period was the completion of the three main input components for SWAT analysis: Land Use, Soil and Slope Definition (WBS-300), and maintenance of ArcGIS 9.1 software license. These targets were almost completed except updated of ArcGIS 9.1 license which failed to be accomplished. Fortunately, the recent availability of open source package MapWindows-SWAT (MW-SWAT ver. 44SR), provided freely from www.waterbase.org by United Nations University (UNU), allowed the chance to complete early than expected all SWAT processing chain. Though it only used a low resolution global input data. SWAT-Indonesia now has the “advantage” to proceed with two options: Arc-SWAT or MW-SWAT. Accordingly, the scenario has been adapted to two-step approach: (1) a “quick yield” effort to complete SWAT chain process within Year-3 using MW-SWAT, and (2) an improved SWAT re-process in Year-4, to fine tuning the existing result with local input data (WBS-300) by applying MW-SWAT or Arc-SWAT option.

Implementation of SWAT in Indonesia is influenced clearly by three factors: (1) the availability of SWAT software, (2) the availability of the required input components, and (3) the difficulty in relation to fragmented land use due to small holder farm size. The last factor is due to the location of study area in Java Island which is heavily populated compared to other parts of Indonesia. In the other hand, the second factor is mainly due to the fact that no nation wide “standard” watershed modeling was consciously selected and implemented systematically in Indonesia. As the consequences, no minimum products of data or map input requirement were established. This is the main reason why inputs in suitable format for SWAT are not readily available, even in the relatively well developed region of Indonesia like Java. Nevertheless, adaptation of SWAT in Indonesia is considered to be a golden opportunity. It provides a starting point to initiate systematically a “standard” watershed modeling in Indonesia, initiated from Nanggung study area.

This Report updates the result of the first step (quick yield) approach, by using open source package MW-SWAT. All SWAT processing chain was successfully completed and plotted by using low resolution global input data. Parallel to this activity, collection of local input data (WBS-300) was completed. Two important issues were found: (1) procedure to prepare local input which suitable to MW-SWAT format, and (2) construction of weather generator file. The 2009 SWAT-SEA Conference will be an excellent opportunity to discuss and solve these issues. The second step (MW-SWAT fine tuning with local input) is expected to be completed in Y-4. If this scenario works well, SWAT will be ready to start the monitoring of the Nanggung sub-watershed coincide with scaling up stage of VAF system.