Response Time of a Canal Pool for Scheduled Water Delivery

Abstract

Estimating the response time of a canal is essential for the open-loop control of an irrigation canal since upstream flow releases must be anticipated to satisfy scheduled demands at irrigation outlets. The authors consider a flow release at the upstream end of a pool to satisfy a side withdrawal at its downstream end. When the flow is released, wave travel time causes the flow change to arrive sometime later downstream, and attenuation causes the flow to arrive gradually downstream such that the peak discharge is further delayed. A clear definition of this response time is proposed based on volume compensation. A linear approach is used to calculate the canal response to a flow release and a withdrawal and then the volume passing at the downstream end of the canal. The approach provides an analytical determination of the time of opening that ensures volume compensation. A practical method to derive this response time is proposed. It is illustrated for a canal for which different downstream boundary conditions are imposed.