 Okay, good morning, good afternoon, good evening, depending on wherever you are. Welcome to this IHE-Doubt alumni online seminar, this is part of our alumni online seminar series where we hear interesting insights from our community. Today we have the privilege to hear from Chopran R. Ahmed, who graduated from IHE-Doubt with an MSE in Water and Sustainable Development exactly one month ago. So she's a new and very welcome member in our alumni family. As so many other IHE-Doubt students, Chopran had made impressive achievements already before she came to doubt. She has a Bachelor's of Science in Chemical Engineering from Cartoon University. Her studies there earned her an award for Best Academic Performance and Best Graduation Project in the Chemical Engineering Department. She's still involved in Cartoon University as a teaching assistant in the Chemical Engineering Department. In 2019, she was a research assistant in the university's Materials and Nanotechnology Research Center. Her experience also includes serving as a production planner in the Dowl Factory for Gum Arabic and working as a math teacher. At IHE-Doubt, she excelled as a student in the first class taking the new one-year MSE in Water and Sustainable Development. And today we will have the pleasure to hear her talk about her thesis work and results. Her thesis is available in the IHE repository, so if you want to know more you can read it all there. She's also working on a paper on the thesis. In addition, Chopran is one of the photos adorning our latest education and training guide. She's right here, which is a really nice publication. If you want some mail to use, you can distribute them to interested people. Drop us an email at communication at unihg.org stating your address and how many copies you want. There's, of course, also an online version. During the seminar, please type your questions in the chat box and we'll pose as many of them as possible to Chopran at the end of her presentation. So, over to you, Chopran, the floor is yours. Thank you, Susana, for the kind words. Thank you, Susana, so much for your kind words and really my pleasure today to present my work about evaluating the sediment trap efficiency of the GERD and its impact on downstream sedimentation rate in Rosario's reservoir. So, first I will start by introducing my study area, which is the Blue Knight. It is a transboundary river between Ethiopia and Sudan, and it originates from Sana Lake. And as many of you now know that it is exhibiting new transformation due to the construction of the GERD, the largest hydropower dam in Africa, with 145 gravity dams. Together, the gravity dam and the sediment dam will provide a total capacity of 73 billion cubic meters. About 130 meters downstream, the Rosario's Reservoir, which is in terms of volume, it is 10 times smaller than the GERD, and here I can show you the confluence of the blue and the white Nile in hat form, and here I might ask you a question. Which one do you think is the blue Nile? So, we have you, Susana here, and I think you have never visited Sudan before, right? Not yet. I really hope to go one day. So, which one is the blue and which one is the white? That's the question. Yeah, the one in the left or the one in the right is the blue Nile. What do you think? Well, the left one is darker, so I will say that is the blue Nile. This is typically what this is, any of these things. These people give the name for the blue Nile, blue, because it is like from our context, wherever the thing is dark, we call it blue azurek. So, from here, this is why we call the blue Nile the blue, because it is more turbide, more dark, and you can compare it with the white Nile here that's much clearer and clean. That was a quick introduction for my study area, but the problem is that first the blue Nile river, as I've said, has a very high sediment load, and that was causing really serious problem downstream, like the Rosaries Reservoir, for example, lost one third of its capacity because of the sedimentation. In the Jezeira scheme, which is one of the largest irrigation scheme in Africa, 80% of the maintenance cost every year goes to the sediment removal, and the problem is growing. There is an increasing trend in the sediment yield of the blue Nile, as stated by many studies, and now the construction and the feeling of the guard is expected to have a significant implication for the water resources and the sediment balance of the blue Nile. Already the Hydraulic Research Center is Sudan reported a significant production in the sediment load downstream after the start of the feeling of the bird, and this also might cause problems such as the erosion, soil fertility decline, and other threats for the aquatic arborus, but also it can have a consequences on the reservoirs themselves. The guard is the capacity of the guard is expected to decrease over time while for the downstream dams, the sedimentation rate will be slower, and here there is a very limited number of research addressing this issue, the sedimentation of the guard and its impact on the downstream dams, and this is going to be the research problem or the research gap that I will fill with my findings. Sorry for some technical issue, so for the research objective, my research objective was first to estimate the dynamic seasonal and annual trap efficiency of the guard, and I mean by the trap efficiency, the percentage of the sediment, the income in the sediment that will be trapped in the reservoir. The second objective is to investigate how the rosaries reservoir trap efficiency will vary and the sedimentation rate of it will vary in response to the reduced sediment influenced by the by the decrease in the sediment caused by the operation of the guard. So the timeline of my study, as you can see here, first in 2011 the construction of the guard started, one year later the rosaries was heightened by 10 meters and in 2020 the feeling of the guard started. So to address my study objective I started first by collecting data from the station, the nearest station to the guard shown in the red color here, and then I consider two cases. First, the first case is that the sediment of the blue nile going directly to rosaries reservoir, and I studied the sedimentation of the rosaries in this case, and the second case I assumed that the sediment of the blue nile will go first to the guard and then the release from the guard will go to the rosaries, and at last I compare the results. Sorry again, I have some technical issue, so let's just start again, I think we've stopped in the research methodology. My research methodology involved first, so my research methodology involved first data collection, screening, gap filling, and at the end I had a record of about 40 years of discharge data and much shorter reports of the sediment I think like about nine years. Then we decided to use a data-driven model to extend the links of the sediment data. Then I used the 3D model for calculating the velocity across the reservoir, and then I used this result to divide the reservoir into compartments and studying then the sedimentation in each compartment. At last I developed a bison code to simulate the reservoir sedimentation using the empirical formulas for the trap efficiency, and for the empirical formula, we have many empirical formulas for the trap efficiency calculation. I chose two, charger and tank. Charger formula is the function in the rhythm of the capacity and the inflow, while tank considering more characteristic about the sediment like the particle size, the settling velocity besides the capacity and the inflow, and it also considers the catchment area. But these two formulas or in general the empirical equations for the trap efficiency are giving just static values. For a specific condition, you just calculate the trap efficiency in that state. What we did, we tried to add dynamic aspect for the model by considering the changes in the capacity that may be due to the changes in the operating level, because each operating level will have a certain capacity or a specific capacity, and also the changes in the capacity due to the accumulation of the sediment, because the model was able to track the cumulative deposit and subtract it each time. Besides that, the model was also able to consider the variability of the inflow, the seasonal and annual variability of the inflow in the trap efficiency calculations. For the reasons how we start first with the data driven model, as I mentioned, first we had long records for discharge and short records for the sediment. First, we tried to use the discharge to calculate the sediment using the rating curve, but we had a very low correlation coefficient, and it is well known that the rating curve for calculating the sediment from the discharge usually are overestimating the sediment values. What we did, we tried to consider another input, which is the precipitation data. We downloaded the CHERP's precipitation data for the study period, and then we used it together with the discharge to estimate the sediment. For the model, we used artificial neural networks, and then we trained the model. Given the datasets of the discharge, the precipitation, and the sediment, we trained the model, and given the datasets, it was trying to get a relationship between these three parameters, and then after the training, we used some data for the testing to validate the model. After the validation, we had a validated model that can receive the discharge and the precipitation and give us the sediment. By that, we were able to create a record of sediment for 37 years as a combination of measured value and predicted value by the model. We divided the data into 70%, I mean the historical data, the measured data, into 70% for training and 30% for testing, and the results of the model was able to capture the increase of the sediment yield of the blue Nile as stated by many studies. Then for that 3D model, we used it to create the velocity map for the reservoir, and that allowed us to identify where are the areas that had the high probability for the sediment deposition, like this one in the dark blue, which is the very low values of the flow velocity. The velocity map also enabled us to divide the reservoir into compartments, as we can see here, and then study the sedimentation in each compartment separately, which is the recommended approach by Ryan to study the sedimentation in a large-scale reservoir. And then for the model, the Bison model for simulating the reservoir sedimentation, we applied first for Rosaris to validate the model, since we have some parametric survey, and we divided the validation into two periods, the 19th and the 20th, because we expected in the 19th, the model might have a higher uncertainty, because it used the Datted River model as the input, and the Datted River model during this period doesn't have any training data. In general, the model was able to capture the decrease in the capacity of the Rosaris reservoir over time, but as expected in the first period, the model underestimates the sedimentation in a Rosaris reservoir, while in the second period, it was giving more accurate results. Then to study the seasonal trap efficiency of the GERD, we applied the model for 37 years, using 10 days time step, and we considered two operating scenarios. Since there is no agreement yet on the operation of the GERD, we consider one scenario of maximizing hydropower from literature, which is the second scenario, as you can see it here in the dashed line, and the second scenario, or scenario one, is assuming a constant operating level of 632, which is the mean of this scenario of maximizing hydropower. Then after applying the model for 37 years, we calculated the average value of the trap efficiency for each time step window, and we plotted together with the inflow and the capacity, operating capacity of the dam, and that enabled us to have two conversant. The first conversant, how the seasonal trap efficiency respond to the changes in the inflow, which we can see here in the first formula, charger formula, we can see the lowest trap efficiency value associated with the peak of the inflow. While for the dam formula, we can see that the highest values of the trap efficiency is resulted from the highest value of the inflow, which is an opposite response. For the second conversant, we can compare how the changes in the operating capacity between the two scenarios resulted in different trap efficiency value, or we can say, in other words, how the trap efficiency formula responded to the changes in the capacity. We can compare that by seeing the two scenarios in the two formulas. For charger, for example, you can see the results of scenario one in the dark column and the results of scenario one in each time step. There was a very slight difference while in the second formula, we can see that there is significant difference between the two trap efficiency value for each scenario, which is indicating that the dam formula is more responsive for the changes in the capacity than the charger formula. In general, the charger formula indicated or estimated higher trap efficiency for the girth, 97%, while the estimated lower value of 91%. And then for the mean annual trap efficiency of the girth, what we did, we calculated the average of each year or the mean for each year. And we can see here, this is the result of charges and this is the result of time. And the dark color for scenario one was the light color for a scenario two. In general, we can notice that there is a very slight difference between the two scenarios in the post formula. In general, estimated higher values than that time. And we can see that there is a decline in the trap efficiency value in the two formula, which has resulted from the decrease in the capacity over time because of the sedimentation. Then we have the storage capacity, how the storage capacity of the girth will decline over time due to the sedimentation. In the two formulas, we can say estimated the same range between 180 to 200 million cubic meter per year for the girth. And we can see from the two graphs that in scenario two, the two formulas all most show the same result. In general, scenario one had the highest sedimentation rate for the charger, while for time the scenario two will have the highest sedimentation rate. We can compare the two scenarios within the two formulas. For the results of the rosaries reservoir, we can see here this is the trap efficiency of the rosaries with the continuous line in the case of there is no girth or without girth. While I represent the results of the trap efficiency with the girth with the dotted line. And from the two graphs, we can see that there is a slower decline or less sharp decline in the trap efficiency value in the case without the girth, while there is a sharp decline in the trap efficiency value in the case of the without existing or without the girth. And that indicates that in the case without the girth, the rosaries will have much slower sedimentation rate, so it will lose its capacity in a slower rate than the case without the girth. And for the annual historic loss, we can see that without the girth, the rosaries will have the annual historic rate of point 52 in scenario one and point 25 in scenario two. While with the girth, the rosaries will have a much smaller sedimentation rate, average annual historic rate of point 07 and point 01. If we convert the two cases, scenario one and scenario two, in the case of the continuous line, which is representing the state of without the girth, we can see also there is a significant difference between the two scenarios. However, they are post-considering the state without the girth. And this is because here we applied the operating rules of Rosaries Reservoir. The operating rules of the Reservoir is using a kind of optimizing the operation to minimize the sedimentation. So during the flood period or the beginning of the flood period, the rosaries Reservoir will have a minimum operating level until the peak of the sediment passes and then the rosaries will start the filling. And usually that happened in September. So we can see that this flushing measure of rosaries was very effective or highly effective and it saved about 9% of the Reservoir capacity over 37 years of operation. And as I mentioned before, we were studying the sedimentation in the girth using 11 compartments and the results show that for the sixth first compartment, there will be a considerable decrease in the volume and that we can see from the decrease in the trap efficiency value in the first six compartments while in the other compartment, the volume will stay almost constant. Here's this graph also showing the deposit in the first compartments and the remaining capacity. And this compartments where we can see the major amount or the majority of the sediment deposition is the episterine, which is suggesting that the girth might have a kind of delta episterine while very low amount of sediment will reach the downside during 37 years of operation. As a conclusion, we can say that the long-term average of the trap efficiency value of values for the girth using Charger formula is 97% ranging from 95 to 99 and using Tam formula, it is going to be about 92, ranging from 89 to 93. And there's also a significant seasonal variability in the trap efficiency value depending on the variability of the flow and the variability of the operating capacity. And there is also a slight difference between the values of the trap efficiency of the two scenarios. In general, POS formula estimated similar values for the cementation rates and the average annual loss of 0.29% per year. For Luzeres reservoir, we can see that the trap efficiency of different ranges and without the girth. In general, the values without the girth is smaller than the values with the girth. And we can see that the sedimentation rate of a Luzeres reservoir will decrease significantly with the girth. And when we compare it with the state of without the girth, it will decrease in scenario one from 30.8 to 4.7 and in scenario two from 16.1 to 1 million tons per year. For the sediment, for the study limitation first, the computational scheme that we described is just assuming that the head water is the only inflow point for both the sediment and the water. And also there was no available data for the bed load. That's why we used the percentage of the bed load and the suspended load from the literature to consider the bed load. Also in the water balance, we didn't consider the evaporation, which is an essential element in the water balance of the reservoirs. For the sediment particle size also we assume it to be constant. However, it can vary over time. For the recommendation of the study first, we recommend that a sensitivity analysis is necessary, especially with the calculation of the reservoir sedimentation because it involves many uncertainties in the measurements of the sediments and measurements of the inflow, and also in the data driven model that we used. Exploring more scenarios also offers a more comprehensive understanding of the sedimentation rate and its responses to different operating strategies. So at last I tried to involve some pictures from our trip to the blue night that was in I think December 2022. It was a very valuable trip for me. I started with a jazira where they were suffering from the deposition of the sediment in the canal. We listened to the operator, to the people from the ministry, and how they were doing the sediment removal measures. Also we listened to the farmers, their fears and their expectations and they really gave me very useful insights. I was really surprised by their understanding of the river and they were expressing it in a very simple and it's really also accurate how the river will eat some parts of the lands and how it will accumulate it to another. So I really appreciate this because it opened my eyes for for me. It opened my eyes for many issues that I will never find it in the literature. So at last I want to thank all the people who contributed to this research for my family and for my friend for their continued support. And that's all from my side and if you have any questions then we can thank you. Yes everyone please type your questions or comments in the chat box so that we can have them addressed. I can start with a question that I'm a bit curious about. If we zoom out a bit and think of the bigger picture, if your findings lead to application, how will it affect the region? I think many people can benefit from my results. For example, the operation of a resource is expected to be changed because it was focusing on the sedimentation management and now they can focus more about meeting the demand downstream or maximizing hydropower because maybe now the sedimentation is not a big issue as a first. And also it can be a way for another studies for soil fertility decline, what will happen to the Zeta skim lands and so on. And also I think it is important for some social studies because some people in the region downstream they're depending on the sediment for treks make up for example and other economical sources. Okay thank you. Let's see if we have anyone who does the question. Oh yeah we have Humphrey Kamwendo. Was the sediment regime downstream of the GERD quickly checked over the proposed period? Does that make sense to you? Can you answer that question? Okay the question is from Humphrey Kamwendo. Was the sediment regime downstream of GERD quickly checked over the proposed period? Over the proposed period there were a continuous measurement of the sediment downstream before and after the construction and I think I have enough records for the two periods so I saw the decline in the sedimentation clearly in the data. Thank you. Thank you and then we have Desaleng Vorku ILF who wonders what do you think the GERD think about the GERD? Is it a threat or advantage for the Roseris reservoir? That's a good question. I don't have the picture. I only answer the part of the sedimentation how the sedimentation rate will change but there are another aspect for example erosion and other problems so I cannot say it will be good or not. I'm just giving what I focused on what will happen to the sedimentation rate and for the sedimentation rate of course it is good because it will be reduced but for other aspects I think we have to get another research done in that area. That's a true scientist answer to that tricky question so good and we move on to Gopakumar who wonders how do the alterations in sediment load due to the GERD construction impact the ecology and environmental dynamics downstream in the Blue Nile basin? Are there potential consequences for aquatic life, agriculture and other ecosystems that rely on the sediment flow? For the aquatic life I expect some threats because there is quite a change from the state before and after. Before the GERD there was water with a high turbidity so the quality of the water would be completely different after when you have a very low level of the sediments. So maybe this change might have some effects or impacts on the aquatic life for the other aspect. What are the potential consequences for aquatic life, agriculture and other ecosystems that rely on sediment flow? The agritation yes but it has two sides for the soil fertility it might cause some decline in the soil fertility because the sediments also carry some nutrients to the soil for example nitrogen and phosphate and for the irrigation scheme when they have some problems with the the sediments in the canal maybe it would be good because then might they save the budget for the sediment removal to do other stuff. Great thank you we have lots of questions coming in here it's great to see and Abad Muhammad Ali wants to know he thanks you for the nice presentation which several others have done and I'll share those thank yous with you later I'm glad that people are happy. So given the significant difference between the two selected equations show chill in time what is the criteria of selecting the equation to maximize the reliability of the calculations? Oh very nice question actually as I've mentioned before there are many equations for the trap efficiency over 28 formulas what we tried to do all of these equations are empirical that they were developed from existing data making correlation with the existing data so we try to find equations that rely on data for reasons why that in terms of volume close to the girth so then we will avoid using the formula for the range out of the ring that was developed for for time formula in particular there was two reservoirs they were very close in in in the capacity and there were two yeah I think two very close to the girth in terms of capacity so that's why we consider the time formula for charge formula it has it one of them I think oldest trap efficiency formula and it has been applied in many reservoirs before so it has been validated for a large number of reservoirs. At one point I think I didn't mention about the time time equation was validated with 18 reservoirs also and I think one of them was close for the capacity of the girth to the capacity of the girth I think 64 billion cubic meter so it might also I think give an indication of the accuracy of this formula to stimulate the trap efficiency of that range of volumes or capacity. Good we move on to the next question because they are coming in what measures this is from Harry Pandit from Nepal what measures do you suggest to minimize downstream impact? Unfortunately I think the girth doesn't have gates for flashing and I think such suggestion needs to consider many design criteria and also the economical visibility so I think some there are some measures like move there are I think some tunnels for the for the sedimentary move well there are many options but it has to be the visibility of all these options should be considered to in order to give a good recommendation for such issue. Indeed and I think that was also like some other questions a little bit beyond your research topic but I'm glad that that you've entered in giving an answer thank you very much for that we have Nazir Khamid who wants to know he was very fascinated by your interaction with the farmers as was I how did you use the information provided by the farmers and to which level did you rely on their information in the research? Unfortunately I didn't cover the social aspect but when I was in Sudan at that period I was trying to put the objective of my research so their views and the interviews with the farmers and also with the operators of Rosarius I helped me to define my research objective mainly but unfortunately they were not considered as the source of data but it was kind of analyzing the problem. Okay thank you for that we have Magali Kuzipuma Ayuke and also thanks for a presentation you did not have a measurement bed load based on it which empirical equation did you use to and I have to do that it doesn't really show there which empirical equation did you use to split the percentage of bed load and suspension material did you analyze the longitudinal position behind the dam which pattern did it have does that make sense? Okay I depend on the literature because there are some reports about the sediment in the blue night the percentage of the suspended and the bed load like they they specify that the total load about 80 percent of it is suspended load and 20 percent of it is a bed load so I use this percentage just to estimate the amount of the bed load from the suspended load. Great thank you and we have some comments asking about sedimentation and how that will affect things and let's see if this is something you can answer Emanuela Mazave wants to know after how many years the level of sedimentation will be unbearable and unbearable might not be a scientific term but I think we get what he needs unbearable like unbearable unbearable as in we just can't take it anymore it's too much after after how after how many years will it be a significant problem? I think even during this study period was significant but we had estimated that the useful life of the guard will be over 600 I think 600 years I'm not really sure about the number but even I think during this period the 37 years of study there was a significant decrease in the in the storage of the guard it's almost I think about 10 percent so I think it is a significant number. Yes thank you and we have David Jansal in the same vein there who wonders about your recommendations regarding the sedimentation issue. As I mentioned before it is another whole study should be done in order to give a good or solid recommendation for this part. That is that is true a very scientific answer so we have more question here on the sedimentation Ali Ahmed once oops now Ali Ahmed I lost his comment here it is how is the effect of the reduced sedimentation of the downstream agricultural plant in the soil fertility again this might be beyond your remit as I just said it was my my study will just give the way for other studies in this field of the soil fertility. Thank you we've also had several uh several commenters asking for your work and I have sent post the link to the uh home thesis which is in the IHDL repository link in the comments box to that and we will also as usual always post the recording of the seminar on YouTube and make it available on the IHD alumni page. Do we have any more questions we have lots of thank you well done coming in into the comments have I missed any questions if I have please alert me in the comments box I think we have perhaps now answered all the questions so we're ready to conclude thank you very much for a fascinating presentation do you want to offer some concluding words perhaps explain what you're working on now. Now I'm going to define more my results and write the scientific article or paper from my findings soon so hopefully we'll find it published somewhere if you need more details so yeah and I'm also now focusing more on the water harvesting water treatment and the sedimentation issue is I think adding adding a lot for my experience and I think the practical value of the research gives me motivation to continue and and try to find any way to improve the results so and I think in our region we need to work on such kind of research that can give evidence based recommendation for the down operators or for other areas indeed great so with that let's conclude our seminar thank you so much for this has been so interesting with all known a lot and we will put it online eventually and stay tuned for the next seminar we'll let you know when that comes out thank you bye bye