 I am Professor Dr. Satish Kumar Kashyat from Walsh and Institute of Technology going to present stream flow hydrograph. Learning outcomes of this particular video. At the end of this session the students will be able to describe the concept of stream flow hydrograph. The students will be able to draw hydrograph using given data. The students will be able to explain significance of stream flow hydrograph with reference to floods influencing human settlements. Coverage. Flood pictorial views we will see, then rainfall on our process we will understand. Typical stream flow hydrograph we will see, we will see the definition of hydrographs and then we will discuss the importance of predicting hydrograph. Here we see a typical picture, a river which is carrying a big flood and this is a bridge. So this can give you the idea that in the rainy seasons how rivers are flooded we will always like to have the information of the flood which is passing a particular section of river at a particular time. This is another picture of flooding in the Pecos River of New Mexico. We observe that this is a river and at the time of floods water is also spread on both the banks of the river to great extent. So those are also called as the flood plains where water reaches during the floods. This is an aerial view of the flooded Ganges that is Ganga river in Alhambad city. Here we observe a picture in Bihar which is the worst flood affected states of India that whenever Ganga and its tributaries are flooded we will find water spreads on both the banks of river and a large area of the ground fields goes under water. So the picture itself will tell you that we should study, we should understand, we should analyze the floods which influence the human settlements in many ways. Why to construct and analyze hydrographs? We construct and analyze the hydrographs to find out the discharge patterns of particular river basin over a period of time to predict the flooding events and to plan flood prevention or flood mitigation measures well in advance. Now this is a picture which shows you the process of a heterologic cycle precipitation surface runoff groundwater flow we can see from this. So whenever there is rainfall that is precipitation, some water will flow over the surface of ground that is overland flow, some water will infiltrate into the ground, some water will once again come out as an interflow on surface water but some water will percolate and move to the deep groundwater. So water which is stored in the ground is taken by the plants for their metabolism, some water which is taken by the plant and again given out by the leaves that is called as transpiration. The groundwater is also not stable groundwater always finds a way very slowly towards the rivers or oceans. So here there is a channel. Now let us come to a definition of hydrograph. Hydrograph is a graphical representation of discharge in cubic versus time. In hours or days at a particular time on the stream or channel which drains the watershed area. Now what is the importance of predicting hydrograph? The hydrograph will enable us to manage the storm water, to identify the flood plans on downstream side, to place the hydraulic structures at safer level. Efficient urban storm water management plans can be defined by knowing the hydrographs. It will help us to design the different types of hydraulic structures and it will minimize the effects of floods because by knowing the hydrographs one can plan the mitigation measures. Now this is a typical storm hydrograph. So here we will understand the hydrograph. So you find that this is a time axis and this is a discharge axis, discharge in cubic meter per second or so. Now in this graph two things are shown. One graph is shown for precipitation or rainfall. So this is from this time to this time we find a rainfall. And the intensity of rainfall is varying with a time and then this hydrograph gives you how water accumulates and starts flowing at a particular river section under consideration. Initially before the storm, before the rainfall the tendency of water that is discharge in the river is reducing but when water starts coming into the river you will find that the discharge starts increasing. So the start of discharge is indicated by this pulverizing limb. Now we observe that there is certain time difference between peak rainfall and the peak discharge time that is called as a lag time. The peak discharge here is reaching here say at this particular time. After the water starts receding in the river channel and this hydrograph falls down in this way which is called as a falling or a recession limb. Now whenever there is water flowing in the river you will also find that there is a percolation of water to the ground water and you will find that this will be the increase in base flow going on in this way. When surface water stops contributing here once again the flow in a channel will be the ground water flow or a base flow. So this is a typical storm hydrograph which we have seen time versus discharge due to surface water as well as ground water. Again the surface water is divided into surface runoff and thorough flow as we discussed previously. Now let us understand the response of a channel to the precipitation characteristics and so on. So the physical characteristics of catchment affect the hydrograph its pattern. What are those properties? It will be land use, the vegetation present in catchment, the type of soil, the drainage area of catchment, the shape of basin, the elevation, the slope of watershed, the topography, the direction and orientation of watershed, drainage network patterns, the ponds, lakes, reservoirs, sinks in the basin which also moderate the stream flow. Now there are also meteorological factors which affect the runoff process. The first is the type of precipitation that is whether it is in form of rain, snow, sleet, the intensity of rainfall, the intense rainfall provides gives high peaks, rainfall amount that is the depth of rainfall, the rainfall duration that is over how much period the rainfall is continued, distribution of rainfall over the watershed, direction of the storm moments, the antecedent precipitation and resulting soil moisture. Other meteorological climate conditions that affect the vapor or the vapor transpiration, the temperature, wind, relative humidity and so on. So all these meteorological factors have a significant effect on the. Now let us understand the impact of various factors on the shape of hydrograph. So time was a discharge, so the how shape of basin, if the shape of basin is in this way you will find in initial stages only there will be high concentration because water reaches in the very shorter time, water reaching from the farthest plate a place takes a long time. Whereas if the shape of basin is in this way in initial stages, so peak will take a time to reach, here there may be two peaks observed because of shape of this watershed or this river basin. The drainage density also matters, where there is good drainage or good drainage density will find the peak will be reached at the earlier time. Whereas drainage density is lesser water will take a time to reach the outlet of the basin and then you will find the hydrograph will be spread over more time. So in this way, now if you see the fern shape type of catchment, the peak will be lower whereas if you see the fern leaf shape type of catchment, so here you will find the all water will appear simultaneously or in lesser time at the outlet of the basin and here you will find that the peak is more and hydrograph will be have a smaller. Questions, the runoff is affected by number 1 type of precipitation, number 2 rain intensity and duration of rainfall, number 3 rain distribution and soil moisture deficiency, number 4 all the above. One more question is the rising limb of hydrograph is also known as S curve, concentration curve, flow mass curve, double mass curve and these are the answers. So here you can observe one more picture, this is the main channel of the river and water spread on both the banks of river. So hydrographs also help the hydropower projects for electricity generation. So this is the intake where this is a river and here we are transferring water to hydropower plant generating water using the available head and again what is listed here. So hydrograph also will be useful for estimating the power potential and the availability of water which is available there for the hydropower plant. So these are the references which I use for this video. Thank you.