HYDRODYNAMIC BEHAVIOR OF A CANAL NETWORK UNDER SIMULTANEOUS SUPPLY AND DEMAND BASED OPERATIONS

摘要

The irrigation network of this study consists of three branch canals (the Machai Branch Canal,rnthe Pehure High Level Canal (PHLC) and the Maira Branch Canal) connected to each other inrnsuch a way that the Machai Branch and the PHLC feed the Maira Branch Canal for providing arnreliable irrigation service. The Machai Branch Canal has limited and erratic discharges and canrnnot fulfill the peak water requirements of the Maira Branch Canal and therefore any deficiency inrnthe supplies to the Maira Branch Canal is automatically compensated by the PHLC. PHLC is anrnautomatic canal and has been equipped with Proportional Integral Derivative (PID) dischargerncontrollers at its head whereas the Machai Branch Canal has fixed supply based operations. ThernMaira Branch Canal is also an automatically downstream controlled irrigation canal, which isrnoperated according to crop water requirements using Crop Based Irrigation Operations (CBIO)rnmodel. Under this scheme of operations the flows remain changing most of the time followingrnthe crop water requirements curve. The frequent changes in discharges keep the canal inrnunsteady state conditions, which affect the functioning of automatic discharge and water levelrnregulation structures. Efficient system operation is a prerequisite for getting better waterrnproductivity and the precise understanding of the behavior of the structures and canal'srnhydrodynamics against such changes is a key for getting effective system operations. In thisrnpaper the canal's hydrodynamic behavior and the automatic structures' functioning have beenrnassessed and suggestions have been provided to fine tune the automatic discharge controllers inrnorder to avoid the oscillatory and abrupt hydrodynamic behavior in the canal. The guidelinesrnhave been provided for the operation of the secondary system for achieving smooth andrnsustainable operations of the canals. In addition to this the effects of any discharge variation inrnthe Machai Branch Canal on the automatic discharge controller's behavior also has beenrnassessed.