QGIS: Reservoir volume from DEM - Kajaki Reservoir, Afghanistan

[@woman_life_freedomiran6791]

I'm so glad that I got to know your channel!!!

[@GeosearchInternational]

Welcome!! All the best, Andreas

[@frenchcookerysnob8251]

As an engineering student specializing in hydrosystems management, your channel is the best thing that ever happened to me !

[@GeosearchInternational]

Thanks for your kind words! All the best, Andreas

[@therealist9052]

Exactly what I was looking for. Thanks so much!

[@GeosearchInternational]

You are most welcome! All the best, Andreas

[@Mallikbilugali]

Please do more videos on geology topics,we r waiting , loved ur explanation.

[@GeosearchInternational]

Hi MALLIKARJUNASWAMY, This video is about a reservoir, but you can use the exact same methodology to work out the volume of a groundwater recharge basin, or an opencast mine. You could even use this approach to figure out the volume of a landfill or other positive topographical feature like a hill. What I would like to say is that all topics dealing with water are in the same family. We should not think that groundwater is separate from surface water. Many of the methods can be used for other parts of the water cycle as well. All the best, Andreas

[@kalm1531]

Well done man!

[@GeosearchInternational]

Thanks @kalm1531 all the best, Andreas

[@engahmadansari1972]

Thank you so much for the excellent work

[@GeosearchInternational]

You are very welcome Eng Ansari! All the best, Andreas

[@cusco4x295]

Thanks for sharing your knowledge

[@GeosearchInternational]

It's my pleasure Cusco! All the best, Andreas

[@anggitotria4582]

thank youuu! you helped me a lott!!

[@GeosearchInternational]

You're welcome! All the best, Andreas

[@rohullahsediqi8289]

Hi! at first i thank you for sharing, my question is (you estimated more accurate after adding elevation correction 15.5, you got this number with help of USGU Report) if we don't have any report data how can find correction number?

[@GeosearchInternational]

Hi Ruhollah, thanks that is a very important question! For any dam built after February 2000 we can develop the Elevation-Area-Capacity curves from the SRTM 30m digital elevation model. However, all the area which was covered by water in February 2000 will be flat in the SRTM30, and we have no way of knowing what the DEM is beneath this water surface. If we have the dam design report, we can get the Elevation-Area-Capacity curves from that. This is what I did for the Kajaki dam. Of course the elevation used in that report was based on a different datum from the WGS84 coordinate system, so you need to find the "magic number" to correct the two datasets. By trial and error you can fit the overlapping curves between the report and the ones calculated from SRTM30 like I did in the video. If you have a reservoir and the dam report is missing, then you should look for old topographical maps. Geo-reference them based on satellite images and digitise the relevant contour lines. From that you can either directly calculate the volume of the area covered by water in February 2000 - for each contour line all the way to the bottom of the reservoir, or create a new DEM based on these contour lines and use that to calculate the parts off the Elevation-Area-Capacity curves that you cannot get from SRTM30. Hope that makes sense. All the best, Andreas

[@dvd5542]

Great tutorial thnx

[@GeosearchInternational]

You're welcome! All the best, Andreas

[@KKoKoRR]

3:11 You didn't change the CRS when save DEM. It is projected to ESRI 54034?

[@GeosearchInternational]

Hi KoKoR - well spotted. Indeed it is a mistake. In Step 6, I extract the DEM using the polygon and then it is saved in the correct equal area projection. That is the reason why the end result is OK, though it would have been better to project the DEM at the start. All the best, Andreas

[@Tom-ks9xl]

This is Brilliant! Concerning the amount of repetitive commands it might be probably worth to either write a little plug in with python or so. That creates the table depending on z value. Maybe there is even already a plug in that we don't know

[@GeosearchInternational]

Hi Tom, Glad you liked it. If you find a faster/better way do let me know! All the best, Andreas

[@atiqullahazad199]

I am so glad to see your videos, but why you select Kajaki Dam for your working area?

[@GeosearchInternational]

Hi Atiqullah, Kajaki is the most important dam in the Helmand River Basin & also there are some interesting studies already completed by the USGS. I wanted to see if they can be replicated using open source data. For example, see my video on the evaporation losses of Kajaki dam. All the best, Andreas

[@habibpopal9270]

I think the results for your volume is 5100 MCM which is a large number compared to the actual reservoir capacity 1700 MCM.

[@GeosearchInternational]

Hi Habib, the maximum capacity @ 2 metres above the spillway is around 1485 MCM. That is an SRTM elevation of 1020m, or an arbitrary project elevation of 1035.5m. When we make the Elevation-Area-Capacity curves we will always include elevations which are way above the maximum fill level. In this case I have gone up to 1050m SRTM, which would give a volume of 5063MCM. Of course this is just theoretical. The reason for extending the curves is in case some politician decides that it would be a good idea to increase the dam height by "x" metres. I think there were some plans to do this for the Kajaki. If the curves are ready, it is very fast to see the impact of this in terms of flooded land area, and increased evaporation losses from the larger surface area of the reservoir. All the best, Andreas

[@enashamed3117]

Thank you for this video .its amazing and very useful.i want to ask you if this method can be used for lakes upstream barrages in river reach or for dams only.

[@GeosearchInternational]

In theory yes, but I would be very careful with rivers as they are constantly changing their profiles, so I'm sure that the SRTM model of 2000 is very different from what it looks like today. All the best, Andreas

[@africanahills2851]

Great video Mr. Andreas. Watching from Kigali, Rwanda. I am a dam engineer. Keep it up. One Question: We are facing issues of measuring/estimating sedimentation levels/volume in our existing reservoirs such as the reservoir of Nyabarongo I hydropower project (location: -1.989096°, 29.633219°). Apart from Bathymetric survey, Any other method can you propose to us in the estimating sedimentation volume within a reservoir? Thx

[@GeosearchInternational]

Hi @africanahills2851 Glad you like the video! I have travelled through Rwanda many times en route to Bukavu in what used to be called Zaire. A beautiful country! Regarding sedimentation issues in reservoirs, I think that is the most important issue after evaporation losses. Bathymetric surveys are expensive, but what you can do is to look at Sentinel satellite images and map the water area at different times, especially when the reservoir levels are going down in the dry season. That way you will see the speed of sediment build-up over the years. The best way to do this is via the Google Earth Engine, but you will need some programming skills. You could also do drone surveys if you need more details. Have a look at: Guidelines for Developing Reservoir Sedimentation Monitoring Plans www.usbr.gov/tsc/techreferences/reservoir/GuidesForDevReservoirSedimentationMonitoringPlans_09-2021_508.pdf Reconnaissance Technique for Reservoir Surveys www.usbr.gov/tsc/techreferences/mands/mands-pdfs/ReconnaissanceTechniqueResSurveys04-2006_508.pdf Good luck & all the best, Andreas

[@africanahills2851]

@@GeosearchInternational Great quick feedback and explanations. I will go through the shared material/documents. Thx a lot. I appreciate your contribution

[@GeosearchInternational]

You are most welcome! All the best, Andreas

[@bibhorbista9808]

1) Is it ok that I got a different result than yours while calculating surface raster volume? Is it because the SRTM images that we import from the plugin are of different time? 2) What does 'count only below base level' mean?

[@GeosearchInternational]

1) There is only one SRTM30 digital elevation model of the world, so the only difference will be if you use a different polygon for your area, or if you have used the wrong method for the volume calculation. 2) Method: 1 - Count Only Below Base Level: only pixels below the base level will add to the volume.

[@frankodoom3360]

please can i get the satellite imagery data of kajaki reservoir which is labeled, n32e065 1arc v3

[@GeosearchInternational]

Hi Frank, n32e065 is the 30m DEM which you can download inside QGIS. I think I explained how to do this in the video: kzbin.info/www/bejne/rHzHhomgec6Zers The satellite image in the video is just the standard ESRI satellite background. All the best, Andreas

[@frankodoom3360]

@@GeosearchInternational ok thank you sir

[@GeosearchInternational]

Welcome Frank, All the best, Andreas

[@motivationalvideo7270]

How to get these file from where plz make video on that

[@GeosearchInternational]

Which file? Have you downloaded the material in the comments section below the video? All the best, Andreas

[@peterserey7768]

Thanks for sharing this wonderful work. I do have a question Can we convert elevation-area-storage capacity into depth-area-storage capacity? Please correct me if i am wrong. I think this would be an elevation level ID 2 - an elevation level ID 1 and accumulate them all together to the rest. Appreciate your through on this. Thanks

[@GeosearchInternational]

Hi Peter, sorry I don't fully understand your question. We can establish a relationship between any of the three key parameters: elevation, area and storage. In other words we can get a polynomial formula that describes elevation-area, area-elevation, area-storage, storage-area, elevation-storage & storage area. If you have depth data, I would convert that into an elevation of the water level that you can relate to your DEM. In any case water depth is not a good parameter to use, because reservoirs will tend to silt up so your zero depth level may change over time. The DEM and all the elevation-area-storage relationships also needs to be updated on a regular basis via bathymetric surveys or you will overestimate the volume in storage as it is reduced over time. This is quite an important issue for all reservoirs. All the best, Andreas

[@peterserey7768]

@@GeosearchInternational Sorry if i did not address my question well. Can we translate or derive the elevation of the reservoir from the DEM into the water depth level? thanks

[@GeosearchInternational]

Hi Peter, can you explain what you mean by "water depth"?

[@peterserey7768]

@@GeosearchInternational water level of the reservoir. Thanks

[@GeosearchInternational]

Hi Peter, The topic of my video is how to do this given old elevation-area-storage curves which are not using the same datum as the SRTM digital elevation model. If there is anything you don't understand in the video let me know. All the best, Andreas

[@Amadraniba]

This is great, how do i get the excel for this calcs?

[@GeosearchInternational]

Hi Fred, the links to files are always in the description below the video: QGIS shape files & Reservoir DEM: bit.ly/3Lc70Ws EXCEL data & calculations: bit.ly/3unSTaz It opens in Google Drive so just click on the download arrow top right. All the best, Andreas