Page - 441 - in Book of Full Papers - Symposium Hydro Engineering

Sedimentation 12,04 million m3 (1994) (1) 27.227 millions m3 (2008) (12) Output Water: Drinking water need 50 l/sec (9) 600 l/sec (2019 SPAM Keburejo) (13) Food: Food production 3 Ton/ha rice (9) 3 Ton/ha (11) Irrigated field 17,800 ha (9) 33,279 ha (11) Irrigation need 11.00 m3/sec (9) 27 m3/sec (10) Energy: Energy production 6,000,000 KWH (9) 92,000,000 KWH (11) Energy need 3m3/sec (9) 24 m3/sec (11) Total water need 14.05 m3/sec 51.6 m3/sec Percentage of input vs. output for water 20% 18% Sedimentation percentage vs. volume effective 26% 7% WEF vs. sedimentation 77% 264% The table shows that at the moment both dams are in a balance for effective WEF nexus need and functioning effectively as the percentage is between 10-25%. Meanwhile, for sedimentation, Sempor data is so outdated (1994), which needs to be updated to the current condition, which should be higher than this. However, even so, using this data, the calculation shows the sedimentation in Sempor is much worse than in Wadaslintang. The comparison for WEF and sedimentation also shows that the percentage for Wadaslintang is about three times better, which corresponds to a better balance for Wadaslintang dam management. Although the data for the dam managers are similar, the condition of Sempor is worse than Wadaslintang. This condition is caused by different the land use of dams’ catchment. This paper shows that lack of coordination for catchment management can happen even though both dams are managed by the same institutions, and this may contribute to the sedimentation problem. This issue can be addressed by introducing and advancing awareness of the water management interrelations to other resources in the river basin level using the Nexus approach. It also recommends the policymakers to make use of the tool for easy visualizations to see these interrelations. 4. CONCLUSION AND RECOMMENDATION In this paper, the nexus tool is used to give a simple overview of what the approach is about and to showcase that it can be used as a fast assessment towards dam management condition. The results also show that the WEF percentage correlates with the dam effective level of storage and water usage, while the sedimentation percentage correlates with the effective volume of the reservoir. Both percentages are needed to see the whether the balance condition of the dams is met. The case study of Wadaslintang in this paper is proven to be by far in more balance towards the WEF and sedimentation condition than the Sempor. 441