Water resources Coastal areas

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2.2 Municipal Administration

Administratively City of Semarang is divided into 16 districts kecamatan and 177 villlages kelurahan. Those districts are: 1. West Semarang District, 2. East Semarang District, 3. Central Semarang District, 4. North Semarang District, 5. South Semarang District, 6. Candisari District, 7. Gajahmungkur District, 8. Gayamsari District, 9. Pedurungan District, 10. Genuk District, 11. Tembalang District, 12. Banyumanik District, 13. Gunungpati District, 14. Mijen District, 15. Ngaliyan District, 16. Tugu District. Figure 2.3. Figure 2.3: City of Semarang Administrative Map Source: http:www.semarangkota.go.id.

2.3 Resource Base

2.3.1 Water resources

The rivers that flow in the City of Semarang include Garang, Kreo and Kripik river; Their flow velocity percentages are respectively 53, 34.7 and 12.3 Government of Semarang City, 2009. From the three rivers, Garang River has the most dominant function for Semarang City, and one of the functions is as water source for Tirta Moedal Water Company. Distribution of the water company is still concentrated in the centre of the city, which are East, North, West, South and Central Semarang. Residents who have not received water supply from the water company usually use shallowdeep ground water to meet their needs. 6 Shallow ground water in the area of Semarang City is at the depth of 3-18 m lowland and 20-40 m highland. Shallow ground water quantity is strongly influenced by the seasons and the surrounding environment. In addition to the shallow ground water the residents also use deep ground water, which is ground water stored in depressed aquifer layer. The depth of this layer is at 50-90 m from the surface and the location of the aquifer is in the northeast of Semarang City and at the mouth of old Garang River located in the confluence of Garang river valley and coastal plains Government of Semarang City, 2009.

2.3.2 Coastal areas

City of Semarang is a port city that is important for Java. Based on the location and shape of coastal physiographic, Semarang Harbour city is located in an open coastal plain. In open coastal plains, high waves resulted from strong winds may hit coastal plains easier. In some coastal plains, rob flooding associated with high tides phenomenon has been observed that can disrupt resident’s economic activities. The northern part of Semarang City is bordered by Java Sea. Centre of economic activities in the coastal areas of Semarang City, are among others focused in the area of Tanjung Mas Port. In this coastal area there are also several fishing activities, such as cultivation pond. In Semarang City also faced with problem of land subsidence. One of the triggering factors of the problem is the high population growth. The growing population will result in increased consumption of ground water. As a result there is decrease in hydraulic pressure in the soil layer that will be followed by decrease in soil surface. This condition will get worse if there is additional load on the surface such as settlements or other building areas. Georisk Project cooperation between Indonesia and German Geological Agency has conducted a research to determine the rate of land subsidence in the area of Semarang City. The data of PSI Persistent Scattered Inferometry in 2002 to 2006 has been used by the Project to build Georisk maps or spatial distribution of the rate of land subsidence in Semarang City. The rate of land subsidence in this region is between 0-1 cmyear and 8-9 cmyear see Figure 2.4. Figure 2.4: The Rate Of Land Subsidence In Semarang City: 7 The highest rate of land subsidence 8-9 cmyear covers most of North Semarang district and Genuk District, while the lowest 0-1 cmyear are in some parts of Tugu District, central part of West Semarang District, and southern parts of the following four districts, namely Central and East Semarang, Gayamsari and Padurungan. Some areas near the coast which has low elevation are susceptible to water inundation caused by rob; while the regions far enough from the coast are susceptible to water inundation due to water overflow as drainage system in the area is inadequate. The distribution of water inundation in Semarang City area can be seen in Figure 2.5. Figure 2.5: Distribution of Inundation Area in Semarang City Source: http:www.semarangkota.go.idThe Rate of Land Subsidence in Semarang City

2.3.3 Water resources