Estimation of carrying capacity of the Gulf of Kachchh, west coast of India in relation to petroleum hydrocarbon through oil spill modeling

Abstract

The Gulf of Kachchh (GoK) is a semi-enclosed basin located in the northern part of the west coast of India, and opens to the Arabian Sea. GoK is about 170 km long and 75 km wide at the mouth, and encompasses several ecosystems. Besides major and minor ports, other industries such as SPMs, refineries and power plants are making use of GoK. For the computation of carrying capacity (CC) with respect to PHc, operational and accidental discharges at SPMs and pipeline leakages have been considered. Extensive field studies show that average baseline value of PHc concentration in GoK waters is 10.0 mu g/l. It is assumed that Gulf being an ecologically sensitive area, PHc concentration should not exceed 50.0 mu g/l. On this basis, a methodology have been devised to estimate CC using a coupled 2D hydrodynamic - oil spill model. The model was run to assess the dissolution of the oil for various meteorological and oceanographic conditions and oil characteristics. In the case of operational discharge from a SPM, a quantity of 3.17 + 10 sup(-6) m sup(3/s spill is assumed, and as this spill is continuous, only a small quantity of oil goes into dissolution compared to the instantaneous spills. Including the baseline value, the PHc concentration (is less than 10.4 mu g/l) due to operational spill is found to be much less than the recommended value. Therefore, normal operational spillage from the SPMs is not a matter of concern. When an accidental discharge of 100 m sup(3)/y (from one SPM) is assumed, the PHc level has reached 24.0 mu g/l for all the 8 SPMs considered, and this level is also within the recommended value. The results suggest that PHc concentration due to pipeline leakage is negligible. Based on this, number of SPMs, which may be required/permitted in the GoK waters is estimated