Seite - 438 - in Book of Full Papers - Symposium Hydro Engineering

in order for the dam management to be declared as an effective balance for the WEF nexus. The lower the percentage shows the yield of water using the reservoir storage is high, for example, the number 10% means the yield of 1m3/sec can be for the usage of 10m3/sec. This shows an effective number, but also questions whether the water input is not too low. If the output is lower than input, this means the capacity of the dam is mostly only for storage, which does not represent an effective balance WEF nexus or multi-purpose dam function. For example, for the number 60%, this means 60m3/sec as input is stored, while the output is only 1m3/sec. This condition can mean the reservoir is in filling mode, so the WEF nexus balance is not effective. Another percentage is used to show the comparison of the sedimentation and volume percentage. Those with higher number show less effective upstream catchment management. For example, the number 50% shows that the volume of the reservoir is no longer in balance, as the age of the dam is half way of its lifetime. The lower the number, the better the condition of the dam. A better balance is shown when the WEF percentage is between 15-25% (showing effective use of water storage function with water usage) and a better balance for sediment percentage is under 10% (also based on the age of the dam). In the meantime, the dams are hypothesized as in a balance, but we will see what the tool will show. The data collection methods being used are site visits, secondary data comparison of ‘water-energy-food’ models and document analysis of published materials. These models are used to seek the balance of sedimentation-water conservation and energy output. A slight adjustment is made to fit the existence of data and the need for the objective of this paper. As a showcase of the Nexus approach, the multi-purpose reservoirs are included (8) in this paper: Sempor and Wadaslintang Dams. Both dams were built in the 1980’s, but data availability constraints in presenting the whole range of time. Thus, the data is using the last ten years data only. 3. RESULTS The results are found using the data from these dams to test the implementation of the Nexus approach in multipurpose reservoirs. They are based on data collected from different sources and put into the adapted nexus tool specified for the approach in this paper. 3.1. DAM MANAGEMENT The main research partner for this paper is the dams’ operation manager: BBWS Serayu Opak. Site visits were done to the dams’ location and their catchment areas to confirm the maps and printed data. The daily operator for both dams is under the BBWS Serayu Opak. However, partnerships of management are done with different aspects of the dam. It is divided based on 438