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- Google Earth or Google Maps (to verify the station metadata).
- High detail vector river shapefile (e.g. hydroSHEDS at https://hydrosheds.cr.usgs.gov/datadownload.php or http://gaia.geosci.unc.edu/rivers/
- GloFAS river network, represented by the upstream area map (https://cds.climate.copernicus.eu/cdsapp#!/dataset/cems-glofas-historical?tab=form)
- GIS software to display shapefiles and maps (e.g. QGIS at https://www.qgis.org/en/site/forusers/index.html)
- Go to Settings/Options/Network and click on "Use proxy for web access".
- Go to plugins and choose QuickMapServices and click install.
- Maps will be available in the Web tab
- A good enhancement could be to use maps (e.g. Bing or satellite maps) in QGIS. This would provide a more complete workspace in QGIS with the real maps, the high-resolution river layer, and the GloFAS river network in one space overlayed onto each other. Steps to achieve this in QGIS-3:
- Excel, python, or whichever software can allow you to plot multiple time series. TSview is a software used to display time series from .csv, .txt, excel or LISFLOOD files (https://git.ecmwf.int/users/mocm/repos/tsview/browse)
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- Use the GIS software and the loaded upstream area maps, river shapefile, and Google Maps (Earth) (or if the Google products are not available in the GIS software then open in a separate website).
- First, check how well the GloFAS river network represents the real rivers in the area.
- Check if the rivers, the main channel(s), and tributaries compare perfectly, well, or if there are minor/major discrepancies.
- Maybe the rivers are not represented at all (e.g. rivers are so close in reality which cannot be resolved in GloFAS), or in some cases, the GloFAS network is simply wrong for some reason (e.g. rivers flow into each other incorrectly, etc.), or the provided station drains only a very small area (i.e. below 1000 km2 or even maybe only few hundred km2) which GloFAS cannot accurately represent.
- Alternatively in some areas of the world real rivers can be difficult to locate even on Google Maps/Earth (i.e. in very dry areas where ephemeral rivers flow only intermittently, or where rivers can change their channels like in big deltas), so in such cases, the GloFAS river network will more likely be incorrect or incomplete.
- Then locate the right GloFAS river channel.
- As an ideal scenario, the provided coordinates allow identifying the river section without uncertainty on Google Maps/Earth.
- The provided upstream area (if available), and thus the match between the provided and modelled areas will often help to increase the confidence, or in some cases, where the location is not so clear on Google Maps (e.g. the point is right at the confluence, and it is not clear which channel it is gauging), the provided upstream area will most likely help to decide about the correct channel (i.e. whether it is the main channel, or the tributary, etc.).
- In some rare cases the right channel cannot be identified due to problems with the GloFAS river network or uncertainties on the provided location (maybe erroneous coordinates, or uncertain position of real rivers in the area), or simply as a consequence of too small catchment area (i.e. below 1000 km2 or even maybe only few hundred km2) of the provided station.
- To help increase the confidence of the river channel match, if possible, also compare the observation time series (if it is available simply plot the time series) with the GloFAS reanalysis time series.
- The GloFAS-ERA5 reanalysis can be downloaded from the Copernicus Climate Data Store (https://cds.climate.copernicus.eu/cdsapp#!/dataset/cems-glofas-historical) and the reanalysis data extracted for the selected GloFAS river location.
- Especially, if there is still some uncertainty about the river match, then moving the selected GloFAS point around, and comparing the reanalysis time series from those points with the observation time series, can highlight problems, wrong provided location, incorrect provided upstream area, etc.
- This step can be especially helpful if the mapping seems problematic and the best model point is ambiguous.
- This step is a manual, subjective process.
Step-3: Compare the river flow time series with nearby stations, if possible
- If the station has a time series associated with it and there are nearby stations in the same catchment, compare the data to against the nearby stations to check if the time series can be trusted or if it requires further investigation.
- In QGIS, individuate nearby upstream/downstream stations.
- Plot the time series using tsview, excel, python, or whichever software can allow you to plot multiple time series
- In case the comparison gives ambiguous results, flag be aware that the station and comment as appropriatemight be in the wrong location.
Step-4: Map
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the station or discard the station from your analysis
- Based on Step-2 and Step-3, the best river pixel should be chosen on the selected GloFAS river channel and a flag (described in the table below) should be assigned to the station. By doing that a user can quickly identify if a station has an issue and filter out stations from any analysis.
- This is also done manually.
- Confidence level and flag assignment:
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- ,
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- the
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- coordinates
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- of
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Station metadata is misleading and the station is mapped with Low/no confidence.
In the comment is specified which metadata does not allow to map the station with higher confidence.
The station is a duplicate, specified in the comment.
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The station was mapped with low/no confidence and it should not be trusted as it is.
The station is a duplicate. It should not be used and should be possibly removed.
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wrong ldd/ ldd not able to represent network
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The station is in the correct place but the ldd does not represent the river system.
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The station seems to be in the right position but the observed discharge vs GLOFAS discharge plot seems very different.
Possible issues:
Wrong time series assigned to the station?
Wrong metadata?
Issues with GLOFAS for that catchment?
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Station seems to be in the correct position with the correct metadata, but unsure of position.
In this case, there were no time series associated with the station or the time series is not helpful in locating the station.
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Even if the metadata provided is partially misleading the station could be mapped on GloFAS. In this case, is very important to add a comment about the mapping situation and the nature of the problems or difficulties.
Possible examples
i.e. the station name and the coordinates are correct but the upstream area provided is completely misleading.
i.e. the station coordinates are incorrect but the upstream area provided, station name, river name, time series allow the user to place the station in the correct GloFAS position.
moderate confidence. The station can be used by the modeller.
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- the chosen pixel will be used to extract the modelled river discharge. If in the previous steps too many discrepancies occured the station should be discarded.