Rainy Season Scenario Climate Change Scenario Development in Semarang City

4.2.3. Dry Season Scenario After Dam Development With Upstream Conservation

Conservation Jatibarang upstream reservoir will provide a better effect for water availability. Reservoir development supported by conservation activities, in 2015 and it is assumed that there will be 3-months long dry season, the number of people without clean water taps served is about 47 of people and that number increased to 58 when the dry season occurred 1 month longer. With the same scenario, by 2050 the number of people without clean water taps service increase at 75 and 80. Table 4.1: Scenario Dry Season in Semarang City Population:1.4 Millions Current Population:1.4 Millions Current Population: 2.9 Millions Next 50 years Population: 2.9 Millions Next 50 years People Uncovered by PDAM W ed by PDAM Water Tap 3 Months Dry Season 60 60 80 80 4 Months Dry Season 70 70 85 85 Post Development of Dam wo Upstream Conservation w Upstream Conservation wo Upstream Conservation w Upstream Conservation 3 Months Dry Season 54 47 78 75 4 Months Dry Season 63 58 82 80

4.2.4. Rainy Season Scenario

Based on trend data in Semarang City, the average of rainy season will take place in 2-3 months. Along with climate change, the rainy season is expected to become longer than 4-6 months. If the current urban drainage masterplan realization is only 9, then in a normal situation 10.8 of Semarang City area will be inundated by floods with a total of 36 days per year. In 50 year a half of the drainage master plan will be realized, the inundated areas will decrease at 6.5 with only 22-day flooding per year. Longer rain season will give effect on the extent of inundation areas. If achievements drainage masterplan has not changed and still the same as present condition, inundated areas will increase at 13. Total flooding-days per year will also increase to 72 days. 46 With the realization of half of the masterplan urban drainage in the next 50 years, a longer rainy season still causes inundation to about 7.8 of city area and the possibility to have a 44 flooding- days per year. With less optimal drainage system at this time, it is estimated about 30 of public and private wells are used by approximately 51,000 households are contaminated. If the rainy season getting intense, the number of wells contaminated will increase, where the number of affected communities will increase to approximately 58,500 households. Repairing drainage system in 50 years from now is estimated a reduction to the number of wells contaminated to 20. However, the number of households utilize these resources will be higher at about 92,800 households. Then if in 50 years from now, a rainy season has become longer the number of people affected will increase to approximately 98,600 households. Table 4.3 Scenario Rainy Season in Semarang City 9 Drainage Masterplan are Implemented Current 50 Drainase Masterplan will be implemented Next 50 years Percentage of Inundated Ar centage of Inundated Areas 2-3 Months Rainy Season 10.8 6.5 4-6 Months Rainy Season 13 7.8 Number of Days with Flooding Number of Days with Flooding 2-3 Months Rainy Season 36 22 4-6 Months Rainy Season 72 44 Flooded Houses and Contaminated W Flooded Houses and Contaminated Wells 2-3 Months Rainy Season 51.000 92.800 4-6 Months Rainy Season 58.500 98.600 Areas Pr eas Prone to Landslide 2-3 Months Rainy Season 23 Sub-district 8 Sub-district 4-6 Months Rainy Season 38 Sub-district 19 Sub-district 47 Landslide prone areas in Semarang City are also predicted to increase along with the rate of extreme precipitation. Based on the previous VA study, there are 23 Sub-districts are categorized as a vulnerable area and have a high slope. The number will increased to 38 Sub-district in 2050 if the rainy season lasts 4-6 months. In the future, improvement of the drainage system is assumed to be able to reduce 65 risk at the normal rainy season 2-3 months and it will reduce 50 risk at the more extreme rainfall season 4-6 months.

4.2.5. Scenario of Flooded Areas due to SLR