Analytical solution for water surface profile along a side weir in a triangular channel

Side weirs are widely used for water level control in irrigation and drainage systems. These structures are also used to divert excess water from a main channel into a side channel. Computation of water surface profile along the side weir is essential to determine the discharge over the side weir. Estimation of discharge over the side weirs is still an important issue. Most previous research works for side weirs were carried out in channels with rectangular, trapezoidal and circular cross sections. An analytical solution for the water surface profile along a side weir is available in the technical literature only for the special case of a rectangular channel on the basis of a constant specific energy assumption (De Marchi’s water surface profile). No analytical solution is available for the case of triangular channel. This research presents an elegant analytical solution for establishing the water surface profile along a side weir in a triangular channel. The solution, which yields a direct computation of the flow profile, should be a useful tool for evaluation and design of side weirs in triangular channels.

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► Analytical solution for water depth along a side weir in a triangular channel.
► Simple estimation of discharge over the side weir.
► Simple equation to design and evaluate the side weir.