Water mass dynamics in Balikpapan Bay, Eastern Kalimantan Indonesia

Abstract

Balikpapan Bay (BB) located 90 km southwest of Delta Mahakam is one of estuarine systems in eastern Kalimantan directly flows into Makassar Strait. Dimension of BB is about 36 km length and between 1-14 km width, with mouth is wider than head of the bay. Water depth is much deeper (18 m) at the middle part of the bay. More than 10 secondary rivers flow into the bay to contribute large amount of freshwater mass flux. To understand physical properties and water mass dynamics, field measurement during high and low tides were conducted. The results shows that the warmer and saltier water mass are dominant at the entrance of the bay at flood period. Warmer and less salty water mass remain in the inner bay. However, during ebb, salinity is slightly decreased near the entrance and freshwater are observed in the inner bay. During both high and low tides condition, vertical stratification of water mass is very weak. The model demonstrates that this is related to large seawater flux brought by flood current from coastal waters, as well as small freshwater influx from river runoffs. Hence, the tidal dynamics significantly controls stratification and dynamics of water mass in the bay.