 Myself, Dr. Satish Kumar Kashi, Walshan Institute of Technology, Solapur, presenting a topic, Reservoir Planning, Estimating Reservoir Capacity of a Dam by Mass Core Method. Learning Outcomes. At the end of this session, the students will be able to explain mass core technique adopted for estimating required reservoir capacity of a dam for particular inflow or clop pattern. And the students will be also able to estimate required reservoir capacity of a dam reservoir for a particular inflow or clop pattern through one example. Overview. We will have a typical view of a dam reservoir. Then we will discuss the mass core method. Thereafter, we will discuss a numerical example on this method. This is a tehri dam from India and the reservoir which is formed by this dam. And our problem is dealing with estimating the capacity of such a reservoir for satisfying a particular inflow or clop pattern to the reservoir. Outflow will be due to demand. These are different storage zones of reservoir with unguided spill bed. So this is a dead storage. This is the conservation storage zone. This is the spillway crest matching with it. This is the full reservoir level. This storage is flood control storage. This is sarsha storage. And then we come up to the maximum water level. So we depend upon this conservation storage for satisfying the demand. For gated spillway, the spillway gates will be up to this level. And thereafter, you can have this maximum water level. Then this spillway crest level. And this is the full reservoir level corresponding to the conservation storage. And this is the top flood control pool. So this is the sarsha storage in this case. Now, let me discuss something about hydrograph and mass core. Hydrograph is a plot of discharge versus time. And mass core is accumulated discharge versus time. Mass core will continuously rise as it is the plot of accumulated inflow. And if constant rate of withdrawal is required from the reservoir, the mass core of demand will be the straight line having a slope equal to demand rate. Let us see through figures. So this is a plot time versus discharge. So you will find discharge goes on varying with a time. And when we go on accumulating this particular flow on y axis with respect to time on x axis, we will be getting this particular mass core or accumulated inflow core. In the same way, we can have, if we have constant demand, the accumulated demand will come out as an inclined straight line. If we have variable demand in this way, we are supposed to get the accumulated demand in this way. Now, the very simple principle is used here. If we have accumulated with respect to time, and if you have cumulative inflow core with respect to time, at the maximum vertical distance in between these two mass cores, mass core of inflow and mass core of demand is going to give the required reservoir capacity. So here we find there are three places where departure is there. Out of that, this is the maximum departure of the mass demand core from the mass inflow core. So this particular distance we need to find in terms of the cumulative inflow and cumulative demand in terms of million cubic meter, that will give us the required reservoir capacity to satisfy this accumulated demand with respect to accumulated inflows. So let us go for two questions. The crest of ungated dam spillway is provided at RL equal to that of its maximum reservoir level, dead storage level, maximum conservation level or none of the above. One more question. The capacity of a storage reservoir can be decided by using the mass core of inflow, the mass core of outflow by both A and B and none of the above. Then we will go to the answers. The crest of ungated dam spillway is provided at RL which is corresponding to maximum conservation level, as we have seen in one of the figures. And the capacity of a storage reservoir can be decided by using both mass core of inflow and mass core of outflow. Let us go to a problem based on the mass cores. This table shows the inflow of water at hydro power generation site over a period of two years. Calculate what maximum uniformly demand can be satisfied by given inflow pattern assuming policy of using total available water. Also calculate required reservoir capacity to use this inflow without allowing any spill of water. Now, here we observe from November 11 to October 13, what is the inflow? So, we observe that the total inflow sum of this column comes out to be 1920 and that is to be utilized over 24 months. So, you can satisfy uniform demand of 80. That is why in this column we have written 80 as an uniform demand. Here we are not allowing any spill and for that we are going to calculate the reservoir capacity. So, the cumulative inflow values are shown here. For example, by the end of November 11, cumulative inflow is 80. By the end of December 11, it is 80 plus 65, that is 145. By the end of January 12, it is 145 plus 60, that is 205 and so on. In the same way, we have cumulative outflow values or cumulative demand values. So, as these are constant 80, 80, 80, it will be coming as 80, 160, 240, 320 and 400 and so on. Now, here graphically you can observe these. So, the monthly inflow pattern is shown by this particular graph. So, naturally the inflows are lesser in the months of December, January, February, March. Again from months of June the inflows increase than demand. Again in the next year, in the same period again inflows are lesser. So, we store this excessive water in the reservoir for which we need capacity and that store water is used in the further part of year when the inflow is less than the demand. That is why we need a reservoir capacity. Again here inflow is more, again here inflow is less than demand. Here we are assuming the constant demand. Now, here it is another graph of cumulative inflow versus cumulative demand. So, you observe here the cumulative demand comes as an inclined straight line going in this way. The cumulative inflow it is going in this way. So, here we find that the cumulative inflow is less than the cumulative demand. So, here in this case we will have to use the water which would have been stored in the reservoir in previous season. Here cumulative inflow is more than cumulative demand. So, here we are going to store the excess water in the reservoir. And then the required reservoir capacity will be some of the is maximum departure here on lower side and maximum departure on upper side. So, here again you find these two departures in between these two lines but these are small. So, maximum departure on upper line is here and maximum departure on lower side is here. So, you will find that the maximum departure here it is in say May 12, 560 minus 340. So, it will give you 220. So, this 220 deficit is to be satisfied from the storage. Also we need this additional 160 that the departure here in September 12 to store the incoming water. So, if you have reservoir capacity of 380 MCM, then you will be able to satisfy this uniform demand in any case even though there is fluctuation in inflow. So, these are the references which are used for developing this presentation. Thank you.