Allocating water for environment and/or instream uses in rivers is often contentious with offstream uses. The benefits and services provided by instream flows are often not well recognized, especially in developing countries where a large portion of the population directly depends upon the river systems. An improved understanding on sharing of water between offstream and instream uses is therefore essential to meet the demand of humans and nature. One of the ways to address this allocation issue is to consider water as an economic good. The objective of this study is to assess the economic value of water for instream uses, in the Teesta River, Bangladesh. Two important instream uses on which the poor rely, fisheries and navigation, are considered for the study. The study develops a relationship between the stream flow and the fish catch (flow-catch model) for the river. A polynomial model is found to be the best fit (p = 0.001) among the several trends analyzed. Using this model the study further establishes a relationship between the total economic values generated from the fisheries and the flow in the river. Marginal value for water from fishery use is calculated by differentiating the latter equation. Another intra-year flow-income relationship is established based on primary survey conducted on the boatmen. Using this relation the marginal value of water for navigation use is determined.