This article intends to give the outline of a basin information system to be generated and managed in order to monitor the increase of urbanization and trend of pollution potential over seven major basins (watersheds) of Istanbul, Turkey. The data from basin monitoring studies of Istanbul Water and Wastewater Management Authority (Istanbul) was used to evaluate the differential settlement and construction. After the urbanization increase is evaluated by means of building/facility areas, the pollution trends are assessed for different time intervals in terms of five parameters by making certain unit load assumptions. The results indicate that residential settlement increased 0.124-0.003% during 29 months. Also in the same period, mean pollution potential of the basins is found to increase 8.747, 3.578, 5.970, 0.922, and 0.145 in terms of tons/day for Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), Suspended Solids (SS), Total Kjeldahl Nitrogen (TKN), and Total Phosphorus (TP), respectively, considering domestic wastewater and diffuse pollution loadings (from urban runoff and feedlots). These results state that monitoring of basins, especially those exposed to intense urbanization, must be conducted periodically and continuously by means of the basin information system as the first step to be able to control the pollution and to take measures against the threats that come with urbanization.