A, Hydraulic Model Investigation of the Babil Stream under Concrete Lined Condition

Hydraulic Model Investigation of the Babil Stream under Concrete Lined Condition

Abstract

The Babil Stream is used to irrigate agricultural lands and supply water treatment stations for
about 36 km from the head regulator at Shatt Al Hillah then heading east to the Main Outfall Drain. Plans
were made to develop the Babil Stream and increase its discharge capacity from its current capacity of
10.5 m3/s to 15m3/s to serve more added agricultural land and lining its whole length by concrete. The
main objective of this paper is to analyze the current and modified conditions of the flow along Babil
Stream by developing a steady state one dimensional hydraulic model utilizing HEC-RAS version 5.0.7
Software. Cross section data for unlined and concrete lined of Babil Stream, water elevation at head
regulator, and the flow outlets, 170 outlet and 11 water treatment stations, along it length were provided
by the Center of Studies and Engineering Designs of the Ministry of Water Resources. The result showed
that the total required discharge of the irrigation outlets and the water treatment stations along Babil
Stream is equal to 16.74 m3/s, which is higher than the design discharge capacity under unlined and
concrete lined conditions. The Babil Stream simulation under unlined condition, with Manning n 0.03,
and concrete lined condition with Manning n 0.015, showed that the stream can accommodate the
discharge of 15 m3/s with a minimum free board of 0.95 m. A sensitivity analysis to Manning n for unlined
and concrete lined conditions showed that the water level at the head regulator is increased by just 0.07
m and 0.1 m, respectively, at a discharge of 15 m3/s. This increase is not significantly affecting the capacity
and the safety of the stream.