Oceanographic studies off Narara Bet, Gulf of Kutch

Abstract

Oceanographic data have been collected in situ along the submarine pipeline route (lat. 22 ° 30'34"N, long. 69 ° 42'04"E to lat. 22 ° 28'06.07"N, long. 69 ° 43'27.33"E) off Narara Bet, Gulf of Kutch, from November 1977 to February 1978. Currents in this area are predominantly tidal with bimodal distributions. Maximum current speeds during spring tides are 0.97 m/sec towards 70 ° during flood, and 0.67 m/sec towards 250 ° during ebb. Maximum flood and ebb currents occur 2 and a half to 4 hr earlier and later to high water, respectively, at all locations. Correlations between tidal ranges at Sikka and tidal currents at locations 1 to 3 have been established (lat. and long. of locations 1 to 3-location 1:22 ° 30'34"N, 69 ° 42'04"E, location 3:22 ° 30'06"N, 69 ° 42'24"E and location 3.22 ° 29'37"N, 69 ° 42'38"E). Calmest months suitable for offshore installations appear to be November to February. Current components perpendicular to the pipeline due to wind, wave, and tide are maximum at surface (1.25 to 1.4 m/sec). These decrease to 0.79 to 0.9 m/sec at mid-depth, and remain nearly the same at bottom. Maximum (27.5 ° C) and minimum (20.1 ° C) sea water temperatures are observed at location 4 (lat. 22 ° 29' 13"N, long. 69 ° 42' 52"E) during April and January, respectively. Diurnal variations of temperature at the surface and near the bottom are about 0.5 ° C, whereas, it is negligible at mid-depth. In general, salinity distribution at all locations shows a slight increase with depth, while conductivity shows a slight decrease with depth. Maximum and minimum salinities are 36.9 and 35.0% Maximum and minimum conductivities of 55.9 and 49.9 mmho have been observed in November and February respectively. Chemical properties of seawater, viz. <i>p</i>H, dissolved oxygen, phosphate and sulphate, have also been discussed. In general, maximum suspended loads are observed at location 3, where the seabed consists of silt and silty clay. Sea water in the area is mainly transparent (93.4 to 99.9%).