IMPROVEMENTS IN PLANNING OF RESERVOIR PROJECTS

Abstract

The monsoon climate of our country necessitates creation of reservoirs for temporal and spatial re-distribution of the water which is an essential feature of the Water Resources Development in our country. The objective of the study presented in this dissertation is to suggest certain improvements in present method of reservoir planning in India to make it more realistic. The suggested improvements have been illustrated by comparing the changes in planning of reservoirs through suggested improvements vis-a-vis the conventional method being followed presently. The study has been carried out on Balpahari Reservoir Project proposed to be constructed in Damodar Basin. As per guidelines of MOWR (1980), the sedimented capacity of the reservoir at the mid point of its estimated life is used for the simulation studies assuming that it will represent the average capacity for its entire life. The demands for various purposes are considered to be constant through out the life of the reservoir and thus the conventional method adopts the `Business as Usual" (BAU) approach does not take into account possible improvements in future such as increase in field application efficiencies with use of micro-irrigation methods, increase in conveyance efficiencies with construction of field channels to carry water up to the farmers' fields and lining of unlined canal systems, reuse and recycling of water, etc. The reservoirs may be planned to get higher benefits during initials years by taking advantage of higher storage capacities which gets reduced with time due to sedimentation. Higher benefits planned for the initial years may be sustained in later years with implementation of improvements which may compensate for the loss of storage capacity of reservoir due to siltation. The comparative study of the two methods shows that the Balpahari project can be planned to supply 270 mgd of water for new M & I water requirements with improved method as compared to 205 mgd with conventional method. The higher supply is possible in initial years because of higher capacities which can be sustained up to end of 35 years (mid point of estimated life of Balpahari reservoir) by demand management such as increasing field application efficiency for dry crops (by phased implementation of micro irrigation) from 65 % to 80 %; increase in conveyance efficiency from 60 % to 70 % (by lining of the conveyance systems and construction of lined field channels in phases) and effecting saving of 6 % in the existing M & I water requirements. The higher benefit may be further sustained by more stringent measures such artificial ground water recharge, rain water harvesting, watershed development, switching from water intensive crops to dry crops, etc. The extent of required improvements at periodical intervals may be worked out at planning stage itself and targets for their implementation may be fixed and action plan prepared accordingly. The planning of the project with suggested improvements will result in higher returns from the Project and thus is better than the conventional method.. The improved methodology can be replicated in the planning of any other reservoir project.