Estimate of Water Residence Times in Tudor Creek, Kenya Based on Sea Surface Heat Fluxes and Observations of the Horizontal Temperature Gradient During Different Seasons

Abstract

Salinity and temperature measurements were carried out in Tudor Creek, Kenya from 1995-98 in order to determine water exchange between the creek and the adjacent Indian Ocean. Data from the Kenya Meteorological Department including gauging data from two small rivers were employed to estimate long-term rainfall, evaporation and river runoff. However, even though the observed salinity gradient in the creek appeared consistent with dry and rain periods, estimates of river runoffs were not good enough to calculate water exchange, based on salt conservation. Runoff in general was also too small to give reliable rating curves (correlation between rainfall and river runoff). For this reason, heat conservation was used for the calculation of water exchange. Although estimates of sea surface heat fluxes were based on coarse global climatology data with large seasonal variations in the net heat flux (from 50-150 Wm -2 ), the result was surprisingly consistent, with similar water exchange during all different seasons. Residence times for the creek waters in relation to the ocean water are between 3-5 days, 5 days for the waters inside the deep inlet. During spring tides, the exchange is about twice as large as during neap tides. Keywords : Kenya, water exchange, sea surface heat fluxes, heat budget, Kenya coastal meteorology West Indian Ocean Journal of Marine Science Vol. 5 (2) 2006: pp. 163-178