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Sustainable use of the available water resource is an important challenge for food security. An irrigation canal system consists of a number of pools connected to each other by control structures. Unsteady flow Saint-Venant equations are used to model the flow in the canal system and these equations are solved using implicit finite difference methods. The canal system is represented as linear time invariant system and the resulting equations are the dynamic equations in state space form. These linearized equations are modelled in Matlab® environment. The control strategy adopted in this research is the downstream control method of operation and the control structures adopted are radial gates and modified radial gates. The unsteady flow model is applied to the chosen study area and the results obtained from the model are used to simulate the dynamics of the canal system using model predictive controller toolbox. The results show that any closed loop controller will work efficiently with the hydraulic model developed. [ABSTRACT FROM AUTHOR]

The impact of untreated effluent from dye industries and domestic sewage that are discharged into the irrigation tank in Pandravedu village in South India was assessed through physico-chemical analysis of water samples and focus group discussion with the community. Thirty-six samples were collected from the study area across three seasons and analysed in the laboratory. The irrigation water quality indices computed indicated that the levels of sodium, salinity and hardness exceeded the permissible limits of irrigation standards. Consequently, rice yield had reduced by 40% in the region, thereby affecting the livelihood of the farmers. The colour of fishes in the tank also changed and their consumption contributed to health-related issues in the village. [ABSTRACT FROM AUTHOR]

Radial gates are widely used to control the flow in irrigation channels and spillways. Radial gates require lower hoisting force and have better discharge characteristics in partial gate openings. The accurate discharge measurement through a radial gate is a challenging problem especially in submerged flow conditions. The coefficient of contraction Cc is an important parameter for accurate discharge measurement in open channels. In this study, an attempt has been made to determine the coefficient of contractionCc and velocity coefficient Cv for radial gates both for free flow and submerged flow conditions. The flow emanating from a gate is similar to the wall jet emerging from a nozzle. The Cc and Cv values under free and submerged flow conditions are obtained from the measured jet velocity and the discharge. The coefficient of discharge values under submerged flow conditions show large variations with submergence and hence discharge characteristics needs to be improved for better control of flow. Hence, experiments are conducted so as to improve the discharge characteristics by modifying the exit geometry of the radial gate by attaching a quarter of an elliptical lip. Three different geometries of elliptical lips were attempted and the results show reasonable increase in the contraction coefficient. [ABSTRACT FROM AUTHOR]