Channel Network Model Research Articles

Dynamic‐Node‐Numbering Concept in Channel Network Model

The Al-Hassa Irrigation and Drainage Authority in The Kingdom of Saudi Arabia covers approximately 8,000 ha of cultivable land. To irrigate this project, a precast concrete open-channel system has been in operation since 1971. This open-channel network, which consists of 19 mains, 178 submains, and 1,641 laterals, has more than 1,800 valves and vertical gates to divert water in different reaches of the system. The water is distributed according to a predefined irrigation schedule. In order to decide gate operating policies, a computer package known as channel network model has been developed to simulate depth and discharge variation with time under unsteady-state condition. This paper introduces dynamic-node-numbering concept in channel network model by which the control devices can be completely closed and the original schematic diagram, node numbering, and corresponding data for the modified system are internally updated without altering the original data files. This paper also addresses other features of the model such as gate operation under low differential head, interactive capabilities of the model, and simulation of large-scale irrigation network.

Flow Simulation Using Channel Network Model

The Al‐Hassa irrigation system, which consists mainly of open concrete canals with different shapes and sizes, is complex in nature due to the presence of features such as gates, bottom falls, and junctions. The distribution of water through such a network is more complicated due to time‐dependent inflow from the springs and reservoirs into the system. In order to decide gate‐operating policies for irrigation scheduling purposes, the unsteady flow phenomenon used throughout the system to simulate depth and discharge at various reaches with time was studied. The applicabilities and limitations of various models for approximating the solution of Saint‐Venant equations were discussed. The applicabilities and limitations of various unsteady flow packages were also reviewed considering Al‐Hassa network configurations. Among all the available packages, the dynamic wave operational (DWOPER) model developed by the National Weather Service was updated, and hydraulic equations on features such as junctions with distributaries, gates of submerged and free‐flow types, and bottom falls were introduced. Other features, such as interactive capability and use of subsystems, were also added. The modified version of DWOPER is known as the Channel Network Model. Parameters such as gate coefficients and Manning's n‐values of the channel network model were calibrated. Depth and discharge at various reaches of a subsystem were simulated and compared with the observed values.