Impacts of Urban and Industrial Development on Groundwater, Bandung, West Java, Indonesia^*)

by : Soetrisno S.^**)

 

Hydrogeologic Features

On the basis of its hyraulic characteristic and its depth, the multi layer aquifers configuration of the Bandung basin may be simplified into two systems :

Shallow aquifers : unconfined, a few meters to around 40 m below the surface, commonly exploitable by dug wells or driven wells, highly vulnerable to pollution.

Deep aquifers : semi to confined, more than 40 m to 250 m below surface, exploitable by bore holes, low to moderate vulnerability to pollution.

Litology aquifers comprise of volcanic products from the volcanic complexes which bordered this basin and lake sediments, were deposited while the central part of the basin was a lake.

The most prominent aquifer is Cibeureum aquifer comprises mainly of arenaceous tuff and volcanic breccias of young volcanic deposits, the depth of the aquifer varies between 50 and 150 m below the ground surface. Its permeability is moderate to high in coarse materials and lava flows, which is average between 111 and 877 m²/day.

Due to its high productivity, the Cibeureum aquifer is the most aquifer in the basin which is intensively exploited, primarily by textile industries.

The other aquifers are Cikapundung aquifer consists of old volcanic deposits and Kosambi aquifer, its lithologic composition is mostly fine materials of lake deposits. Both aquifers have low to medium productivity, 112 to 150 m²/day, therefore are not so exploitable as the Cikapundung aquifer.

Groundwater flow across the elevation of 1000 m above mean sea level (amsl) to the basin is calculated about 107 million m³/year (Schmidt and Tirtomihardjo, 1991), where about 70 % of which coming from the north.

The northern area of the basin which is situated at elevations between 1050 and 1300 amsl, based on the natural stable isotope content of groundwater in the basin, is considered as the main recharge area of the groundwater exploited in the basin (Geyh, 1990).

Natural groundwater quality in the basin is charecterized by its low salinity (electrical conductivity < 500 uS/cm) on the mountain slopes, and increased to moderate values (500 - 1000 uS/cm) towards the lower parts of the basin. Predominance HCO₃ (45 - 90 meq%), low content of SO₄ (< 20 meq%), and high concentrations of Fe (exceeding 1 mg/l) which occur practically in all areas of the basin, are considered typical for the hydrogeologic condition prevailing in the Bandung basin.