OPTIMAL PLANNING AND OPERATION OF A WATER TRANSFER LINK

Abstract

The National Water Development agency (NWDA), Ministry of water Resources, Government of India has carried out studied on inter basin water transfer in India. It has identified 30 links for preparation of feasibility reports and has prepared feasibility reports of all the 30 links. This entails construction of large river linking projects, which warrants sound investigation, careful planning and huge expenditure. A faulty implementation of these projects may be more harmful than doing nothing at all. The studies for most of these rivers linking are at their initial stages. It is felt that the application of system analysis techniques will help in better planning for these Herculean tasks. The proposed Ken-Betwa link under the peninsular rivers development plan is considered for this study. Inter-basin transfer of water is a gigantic exercise encompassing wide spectrum of fields and is highly complex. The evaluation of such an exercise can best be accomplished with the help of systems analysis. There are a number of techniques employed in systems analysis. The most important of all is optimization by linear programming where the objective function and constraints are linear functions of decision variables. Among different L.P. models, Reservoir Yield Model has many distinct advantages. It has the advantage of dealing with very large size of problem efficiently. As compared to the complete model, there is a substantial reduction in the problem size with reasonable estimates of over-year and within-year reservoir capacity requirements. Further the model has advantages of taking into account the critical year flows and allowable deficit in a dry year. The integrated reservoir yield model (IRYM) and multi objective fuzzy linear programming, model (MOFLP) are applied to the Ken-Betwa water transfer link. The Ken-Betwa link project is located in the state of Madhya Pradesh and Uttar Pradesh in Central India. It is proposed to transfer 1020 MCM of water from proposed Daudhan reservoir in Ken basin to existing Barwa Sagar reservoir in Betwa basin. Only major and medium reservoir projects have been considered in the study. The contributions of the minor irrigation projects have been lumped together for their contributions to the inflow, utilisations and demand scenario. iii For the inflow data, the period chosen for analysis is 20 years i.e., from 1980-81 to 1999-2000. Within year analysis has been made for 12 within-years time periods for the critical year. The water year in India starts in the month of June and ends in May. Annual reliabilities for the firm and secondary yields considered are 95.2 percent and 76.2 percent based on Weibull plotting position for a data series of 20 years, respectively. The net inflow series at each project are calculated by the basin water balance method from the discharge data available at nearby river gauging site. In order to process voluminous data available and received from different organisations in different formats and to place them on uniform platform, different FORTRAN programs are written and utilised. Failure years at each project are identified from the respective net inflow series. The inflow fractions in within-year time periods are calculated for each reservoir considering inflow of the driest year. Storage area curves (linearized over dead storage) are used for computation of evaporation parameters. Demands from different sectors have been considered for a time horizon of 2050 AD. The reason for adopting the planning horizon is due to the fact that the population in India is expected to stabilise in 2050 AD and consequently the demand patterns will also be realistic. The gross irrigation water requirements at each within-year time period of the proposed crop plan under each project is estimated by using FAO-56. Population of the basin in year 2001 is calculated from the district census data and then projected for year 2050 by medium variant population growth rate. As given in U.N. Publication ‘World Population Prospects – 2004 revision’the medium variant population growth rate is applicable for India. Population of a sub-basin is distributed proportionately among all the projects in proportion of their respective culturable/cultivable command area (CCA). Municipal and industrial water demand at each project is calculated for projected population. Site-specific values of allowable percentage yield (failure fraction) for satisfying the project specific demands as far as possible in successful years have been considered in the study. Protein and calorie requirements of the total as well as of the agricultural population have been computed. On the basis of protein and calorie requirements for agricultural population and crop production the water demand to meet the minimum food requirements for agricultural population have been computed for each project. After the flow parameters or the supply parameters, demand parameters and the parameters pertaining to the physical parameters are known, they are put to the model. In order to write the large number of equations into the solver, again FORTRAN programmes are used. iv The matrix so generated is solved by using LINDO software. The study is limited to the surface water resources only. The fuzzy approach is applied using the multi objective fuzzy linear programming model (MOFLP) to obtain the solution of the problem to obtain some compromise solution in the purview of prevailing conflicting water issues, which exist everywhere these days. The two fuzzy objectives were the within year firm and secondary reservoir yields available from all the reservoirs in the system to meet various existing and future water needs in the system. Continuous hedging rule is used to define another set of rules for Daudhan reservoir operation. Systems analysis techniques were successfully applied to solve the large scale Ken-Betwa Link water transfer problem in space and time. The model IRYM was used for planning and the model MOFLP was used for the operation of the Daudhan reservoir in Ken basin. Two cases of with and without water exports were considered. The outcome of the results have been analysed and put in Chapter 8 and Chapter 9. (A) On the basis of the results following conclusions were drawn from planning model (1) With export the total cropped intensity achieved for Betwa system is 73.1% of the target total cropped intensity. Without export the total cropped intensity of the reservoirs in Betwa basin varies from 100% to 2.2%. (2) With export the total cropped intensity achieved at Daudhan reservoir is 9.93% of the target total cropped intensity, whereas without export it is 84.67%. (3) The expected within year reservoir storage without export for Betwa system would vary between 55.21% and 25.98% of the reservoir storage capacity. (4) The expected within year reservoir storage with export at Daudhan would vary between 3.98% and 0.004% of the reservoir storage capacity. (5) The expected within year reservoir storage without export at Daudhan would vary between 48.97% and 8.8% of the reservoir storage capacity. (B) On the basis of the results following conclusions were drawn from operation model (1) With export the total cropped intensity achieved at Daudhan reservoir is 6.9% of the target total cropped intensity, whereas without export it is 85.13%. v (2) The expected within year reservoir storage with export at Daudhan would vary between 3.72% and 0.71% of the reservoir storage capacity. (3) The expected within year reservoir storage without export at Daudhan would vary between 48.97% and 8.8% of the reservoir storage capacity. (C) On the basis of the results following conclusions were drawn regarding Daudhan exporting reservoir (1) The water export at Daudhan is expected to meet 95.63% of its proposed annual export target demand. Except for the month of July all the other seven months of for which the export is needed would meet their proposed water requirements. There would be a short fall of 31.81% in the month of July. (2) Initial rule curve defining lower limits on the storages to be maintained for each within year periods during reservoir operation were derived. (3) CHR is used to define another set of rules for Daudhan reservoir operation given by hedging trigger factors. These hedging trigger factors obtained for each month control releases to be made from reservoir.