Estimation of Instream Flow Requirements for Fish

Flows required for sustaining fish population in a stream are examined in this study. The instream flow incremental methodology (IFIM) which has been developed for estimating these flows requires data which are not commonly available and are expensive to acquire. Other methods to estimate instream flows, which are based only on flow rates, do not consider the characteristics of the fish population in the stream and hence are unrealistic. A modification of the IFIM is proposed in this study. Various factors which are involved in the modification are investigated. Based on these investigations, a method which is much less data intensive than the IFIM but which gives results of the same order of magnitude as the IFIM is proposed. The method is illustrated by using data from streams in Indiana.