ABSTRACT
Measuring and controlling discharge in channels is perhaps one of the more obvious uses of hydraulic structures (Figure 6.1). Large irrigation networks require structures at each canal junction to measure and control discharge so that there is a fair and equitable distribution of water. It is not enough just to construct a canal junction and hope that the ow will divide itself properly between the two. Natural rivers too need regular ow measurement so that engineers can make sure there is an adequate supply to meet the growing demands for domestic and industrial uses as well as maintaining base ows for environmental purposes. It is important to ensure that minimum base ows are maintained in dry summer periods to protect sh stocks and environmentally sensitive wetlands. Flood ows are also measured so that adequate precautions can be taken to avoid or control ooding, particularly in urban areas where damage can be very costly.
