Flow measuring devices show good applicability within a limited range of discharge to be measured. However, in small watershed. when rainfall is not uniformly distributed. it ensures considerable fluctuation of flows. The existing devices are not appropriate and the compound weir is needed for flow measurement. A theory is developed whose application is reasonably justified by the laboratory experiments. The discharge equation of the form o = KHn is formulated. The average values of K and n are found to be 3.31 and 2.75 respectively. Such unique relationship offers a practical basis for discharge measurement. The discharge coefficients (C 1 and C2 ) for theoretically derived equation are also determined. A comparison of the theory with the observations indicates a fair agreement
