Total freshwater inflow from surface channels and from direct precipitation on water surfaces into the Houston Ship Channel and Galveston Bay were determined for a model study of Houston Ship Channel, Houston, Texas. Daily discharges were computed at 14 model discharge stations for the period April 14 to July 28, 1973. The mouth of each major tributary to the Houston Ship Channel and Galveston Bay was designated as a model discharge station. Streamflow and rainfall on the stream surface was projected to these stations on the basis of nearby gaged streamflow and measured rainfall.