Pakistan Research Repository

EFFECT OF VARYING DISCHARGES ON THE EQUITY OF WATER DISTRIBUTION IN THE IRRIGATION SYSTEM

Bhutta, Muhammad Nawaz (1990) EFFECT OF VARYING DISCHARGES ON THE EQUITY OF WATER DISTRIBUTION IN THE IRRIGATION SYSTEM. PhD thesis, University of Engineering & Technology, Lahore.

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Abstract

This study was conducted at three distributaries of Upper Gugera Branch of Lower Chenab Canal, Punjab Province, Pakistan. Mananwala and Lagar Distributaries are in the head reach of the channel and Pir Mahal Distributary is at the tail. Discharge of these distributaries and of selected outlets of these distributaries were measured. Field observation indicate that water deliveries at the head of distributaries are rarely in accordance with the original design criteria. The discharge at the head of the distributaries (perennial) is lower than 75 percent of the design for a period varying from 111 days to 198 days in a year. Field measurement indicate that the distribution of surface water between the outlets of a distributary is substantially inequitable when the original design parameters of distributaries no longer prevail. The average discharge delivered to the outlets varies from 250 (head reach) to 0 (tail reach) percent of design values. The data suggest that two design assumptions for outlets are no longer valid; constant water level in the distributary and modular flow conditions of outlets. The data also suggest that the intake structure of a secondary channel should be a gated one to attain reliable water supplies. Moreover, active management, e.g. altering position of stop logs from horizontal to vertical at the head of a distributary can reduce variation of water deliveries to the distributaries. A computer model Mistral was adopted for the evaluation of management options. Tests performed by the model suggest that under current physical conditions the combination of rotation between the distributaries and along the distributaries can improve the equity conditions of the irrigation system. For example in the case of Lagar Dsitributary the discharge of tail outlets can be increased by 3 times of their existing discharge by introducing rotation between the tail of the distributary and Jhinda Minor. There wll be a small decrease in the discharge of Jhinda Minor by adopting this option. A combination of rotation between the distributaries and along the distributaries can increase the discharge of tail outlets up to 7 times of their existing discharges. The results of the model suggest that if the original design parameter of a distributary are restored, re-adjustment of non-modular and tempered outlets is necessary before equity of water distribution can be achieved.

Item Type:Thesis (PhD)
Uncontrolled Keywords:variability, water deliveries, canals management, head of distributary, discharge, water supplies, surface water, varying discharges, water distribution
Subjects:Agriculture & Veterinary Sciences(a) > Agriculture(a1)
ID Code:539
Deposited By:Mr. Muhammad Asif
Deposited On:28 Sep 2006
Last Modified:04 Oct 2007 21:01

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