Abstract:
Elevation-Area-Capacity (EAC) curves of a storage reservoir are among the primary
requirements for various kind of reservoir analysis such as reservoir flood routing, reservoir
operation analysis, reservoir classification, and reservoir sediment distribution. A river basin
may contain a large number of reservoirs/hydraulic structures. Though some of the general
details like MDDL, FRL, and storage capacity/reservoir area at FRL and MDDL may be
available from various sources (say, web site of India WRIS), it may be difficult to gather
EAC tables for various reservoirs.
In this study, an effort has been made to characterize the elevation-area and elevationcapacity
curves for Indian reservoirs. The elevation-area-capacity tables of 84 Indian
reservoirs have been used to develop such relationships. Depending on the availability of type
and range of original and revised EAC tables for different reservoirs, the reservoirs have been
classified into four types: Gorge, Hill, Flood plain – foothill, and Lake. Dimensionless plots
(relative depth vs. relative area or relative capacity) in the live storage zone of reservoirs in
normal and Log scales have been prepared for each reservoir. Such plots have been clubbed
for all the reservoirs for deriving representative unique mathematical equations for the area
and capacity curves. The methodology has been programmed in MS-EXCEL. From the
available plots, average dimensionless curves have been plotted and generalized
mathematical equations have been derived which can be used to approximate the elevationarea
and elevation-capacity curves within the live storage zone of a reservoir.
In the study, the developed mathematical relationships (within the live storage zone)
and the method proposed by J. Mohammadzadeh-Habili et. al (2009) have been used to
investigate their applicability for Indian reservoirs. A number of reservoirs, for which the
data requirements of the two methods could be met, have been selected and comparative plots
of areas and capacities from the two methods have been prepared in conjunction with the
original curves. It is seen that the two methods approximate the intermediate areas and
capacities quite close to the observed values.
However, the mathematical relationships developed in this study are applicable only
in the live storage zone of a reservoir and do not take into account the type of reservoir under
consideration. Since average relationships have been worked out, the mathematical
relationships may over or under-estimate the intermediate area and capacity values for some
reservoirs depending on the location of their dimensionless area and capacity curves with
respect to the average curve. On the other hand, method proposed by J. Mohammadzadeh-
Habili et. al (2009) provides area and capacity estimates in the full range of the reservoir and
also accounts for the characteristics of a reservoir in terms of reservoir coefficient.
The developed equations only approximate the intermediate area and capacity curves
of a reservoir. For those analyses which are highly sensitive to the accurate specification of
reservoir areas and capacities at intermediate elevations, observed elevation-area-capacity
tables may be used.