Title: Computation of gradually varied flow in channel networks with hydraulic structures

Committee: W. Silva-Araya, J. River-Santos, J. Gustavo-Gutierrez

Degree/Institution:  Master of Science in Civil Engineering from the University of Puerto Rico at Mayaguez

Irrigation canals transport water from a source, such as a natural river or a reservoir, to a crop field or a community, making them vital for agriculture. This research develops a computer model to determine the water levels and discharges in complex irrigation channel networks with hydraulic structures to control water distribution. The proposed algorithm, Simultaneous Solution Method (SSM), solves simultaneously the mass and energy equations for gradually varied flow as well as equations to analyze and/or design lateral weirs, sluice gates, and inverted siphons. The scope of this research is limited to subcritical flow conditions. Four case studies are analyzed, from which three are idealized channel systems and one is a real-life channel system located on a segment of the Lajas Valley Irrigation District Channel System (LVIDS). These were analyzed using the SSM. Two of the proposed case studies were also solved using the Standard Step Method (StdSM), which is used on the HEC-RAS software. Two numerical solvers, the Bi-Conjugate Gradient Stabilizer Method (BiCGSTAB) and the Gauss Elimination Method (GEM), were used to find the solution of the nonlinear system of equations. Results based on a percentage error analysis, computed with the Direct Step Method, showed that the SSM had a less significant degree of error when compared to the StdSM. In addition, the BiCGSTAB solved the numerical system faster than the GEM and converged successfully in all the case studies proposed. The SSM proved to be excellent for determining water depths, flow velocity, and diverted lateral flow through weirs and sluice gates, and proved to be comparatively easier to execute than the other available models.

Publication Language: English

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