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The lower stretch of Gangetic delta in the Indian sub-continent is noted for its rich mangrove biodiversity, natural calamities, and livelihood-supporting matrix of millions of people and is the only mangrove base of Royal Bengal tiger (Panthera tigris tigris) in the planet Earth. The present trend of industrialization, urbanization and construction of barrage in the upstream zone has changed the landscape of the deltaic complex and the characteristics of the aquatic sub-system have also changed accordingly. This ecosystem offers an ideal site to study a number of physico-chemical parameters in relation to changing scenario of the region. The presence of heavily populated cities of Kolkata, Howrah and the Haldia industrial belt on the bank of the Hooghly estuary has made the mighty River Ganga highly vulnerable to anthropogenic stress. Spatial and tidal variations of important physico-chemical parameters in the Hooghly estuarine stretch of Gangetic delta complex were studied during the summer month April, 2008. The water quality reflects the impact of Bay of Bengal (sea) water almost on all the variables as revealed from the significant difference of parameter values in high and low tides (except surface water temperature and potassium). The 12 selected stations from the upstream to downstream regions exhibited uniformity with respect to surface water temperature. Significant spatial variations (at 5% level of significance) were observed with respect to parameters like surface water salinity, pH, alkalinity, DO, BOD, COD, NO3, PO4, SiO3, extinction coefficient, SO4, Na, K, Cl and total nitrogen. Along with tidal influences, the anthropogenic factors contributed by the adjacent cities and towns exert a regulatory influence on parameters like BOD, COD, NO3, PO4, extinction coefficient, SO4 and total nitrogen. [ABSTRACT FROM AUTHOR]