Laboratory 4 - Weir Flow Background Weirs are used on rivers, small creeks, spillways and other manmade streams to control and monitor the quantity of water that passes through it. Weirs can be utilized in operations as simple as an irrigation channel and as complicated as dam spillways. Weirs can be divided into broad-crested and sharp-crested. In this laboratory, we will only study sharp crested weirs. Sharp crested weirs are those whose width along the channel is negligible, as shown in Figure 1. The two types of sharp crested weirs studied in this lab will be a V-notch weir and a rectangular weir. Diagrams of these two weirs are presented in Figures 2 and 3. Figure 1 - Schematic of the Cross-section of a Weir =90 Figure 2 - Rectangular Sharp-Crested Weir Figure 3 - V-Notch Sharp-Crested Weir With a weir system, engineers can monitor flow by measuring the height of the water through the weir (H) and using an empirical equation. For the weirs studied in this laboratory, the following equations will apply: Rectangular Sharp-Crested Weir: Q = 1.84*B*H3/2 (1) V-Notch Sharp-Crested Weir: Q = 1.38*H5/2 (2) Where: Q = flow rate (m3/s) H = head over the