Water availability of Akelamo River, Obi Island, South Halmahera

Abstract

The nickel mining industry's activities are not spared from the high quantity of water demand, such as those of Harita Nickel Indonesia, a company located in Obi Island, South Halmahera. As one of the largest nickel mining companies that uphold environmental conservation, Harita Nickel Indonesia conducted this study to identify and analyze water availability to ensure the company's and local residents' water needs. One of the water resources in this study is Akelamo River, which has a 254.99 Km2 catchment area (covering the catchment area of Karo Lake upstream). Referring to SNI 6738:2015, water availability can be indicated by the amount of dependable flow based on an 80% probability of occurrence. This calculation is carried out using F.J. Mock method that heavily relies on six (6) defining variables: Reflection coefficient (r), Exposed surface (m;%), Soil moisture capacity (ISMC), Infiltration coefficient (if), Flow recession constant (k), and Percentage factor (PF). Based on the method and conditions of this location, it is calculated that the dependable flow Q80 of the Akelamo River is 6.2 m3/sec. It should be noted that this figure only represents overflow discharge and does not include the amount of water currently stored in the water body. This availability study can be continued with a water balance analysis according to the planned water demand or even as a consideration in hydrological infrastructure planning such as dams.