 Hello, this is Hans van der Klaas, Senior Lecturer at ITG Delft Institute for Water Education. In this video I am going to demonstrate how to use hydrological tools from PC Raster in QGIS. Just a few, I will not cover all of them. I will start with this downloaded SRTM digital elevation model, which has been projected, but it is in TIFF format, in GeoTIFF, and I am going to convert it to the PC Raster format. The output data type is scalar, because these are continuous values, and I call the output DEM, and make sure it has the extension dot map, so we can recognize it. Let's remove the TIFF file, not to get confused, because we will further work with the map file. Most of these hydrological tools use the local drain direction, which is a flow direction map. We can create it using the LDD create tool, which has many parameters. Let me show you the documentation for the explanation of these parameters. Meanwhile, it can run the tool that takes a little bit. It is basically combining the fill sinks algorithm to generate the flow direction. The flow direction is then the result, with the encoding based on the numeric path of your keyboard. These are the different parameters with which you can control the filling, and here you see some examples of the calculation. If you just want to fill it completely, you use very high values, like I do with the default here in the tool. When it's done, you will see this result, and it has, for each pixel, the flow direction encoded in the values of the numeric path of your keyboard. Which means 8 is north, 2 is south, etc. With LDD create DEM, you can make a corrected DEM, which is normally the result of the fill sinks algorithm. There are other tools, like LDD distance, where you can calculate distance, based on the flow direction, instead of Euclidean distance. But let's try some other tools. I'm going to calculate the stream order, which is the strahler order, and the input is the drain direction, and I define the output, the file name strahler, calculated. And there you see the result, you can style it. Here I use single-demp pseudo-color, but it's better to use palleted unique values, because this is an ordinal result. Now, I also want to calculate catchments, and I use the pit tool for that. The input is the local drain direction, and the output are the depressions that it finds in the elevation model, in the hydrologically corrected elevation model, based on the LDD result. These are these points, and we can assume that these are outlets of catchments. These points are also an ordinal scale, they have a unique number, and I can then use the catchment tool, use the LDD as an input, and the outlets that I have calculated from the pits tool as an input, and then I can calculate the catchments. I run the tool, and here the result is a nominal map with a unique value for each catchment that drains into those pits. You can also accumulate the flow with the aquiflux operation, LDD is the input, but it needs a material layer, and I just want to set the material to a value of 1 for all cells. So I use the spatial tool to convert a value into a map which has that value for each cell. So I'm going to use a value of 1, and I want the scalar output. I use a mask there, the catchments, then I give an output name which is 1s, so I have a map with only value 1 in it, in scalar, data type, then I can go back to the aquiflux tool, I can use the LDD, and I use the 1s, so it will accumulate a value of 1 that is put on the catchment, or on the DEM, and then following the flow direction it will accumulate the values. So basically it gives us how many cells drain into a certain point, and here we see the result with of course the largest accumulation in the river, and you can determine the river from there. Another nice tool is the path tool. It needs the LDD and it needs a point raster, and then we can calculate the path of that point to the outlet. And I can define a point here, make sure you are in a pen tool, if you click right then you can copy the coordinate of that point, and you can paste it in notepad, and give it an ID number, I call it 1, I call it location, and then I can use the column file to PC raster map tool, and I use this location text file, and I use a mask, LDD, and I need it as a boolean, so I declare it here as a boolean, and I can save it to a map file, click run, and let's style it here, boolean 1, but it has missing values for all the other pixels in the area, and I need zeros, so I'm going to use the cover tool, but the cover tool then needs another layer with zeros, so I'm first going to make a layer with zeros, spatial, zero, and it needs to be boolean, because our map needs to be boolean, and I call this zeros boolean, and then I can use the cover tool, and then I can use as an input the location layer, and then I cover all the missing values with the zeros, from zeros boolean, and I save it then to the name location boolean, which will have zeros and ones, the existing ones, and the added zeros, and here we see that it has zeros and ones, the only pixel with a one is very small, so we can't really see it, so it would be good to use the spread max zone tool for that to make it a bit visible, but then I need another zeros, because it needs the zeros as a scalar, and not as a boolean, otherwise it wouldn't work, so I use here as the points locations boolean, the initial friction is zero scalar, and the friction layer are the ones, which are also scalar, and then let's try a value and see if it becomes visible, let's use 500 to start with, doesn't look like I can see it, and you need to make it a bit bigger, so make sure that all the inputs are correctly chosen, and I use now a maximum distance of a kilometer, and now I can see the point, which was otherwise not so visible only when we zoom in, you can see it somewhere, and what I'm going to do now is to use the path tool from this point to the outlet to find its path to the outlet, so use an LDD, and then the location boolean, and I call the output path to outlet, and run it, and there we see it, let's change the styling a bit, it's boolean so I use pelleted unique values, I remove the zeros, and then I can combine it with the DEM, and then I can see the path over the landscape, so all water from that point will go to the outlet via this path, so all these tools can also be used in the graphical modular and combined with other QGIS tools, so this was just a quick demo to show you what you can do with the hydrological tools from PC Raster in QGIS.