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I was wondering if there are any hydrologically correct river-channel data available for download for Africa?

By hydrologically correct, I mean

  1. the topology should be correct. Connected river reaches should be connected in the GIS file.

  2. there should be (ideally ) flow directions on the polylines reflecting real flow directions

I looked at VMAP0 data, the rivers are broken and disconnected like this:

enter image description here

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  • The whole of Africa or any African countries in particular? – user35594 Oct 21 '14 at 22:45
  • I am specifically interested in West African countries covering the Niger river. – tinlyx Oct 21 '14 at 22:47
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    @WhiteboxDev Thanks for the pointer.My concern with water-course data derived from DEM is that there are too many river features (see e.g. the HyroSHEDs data). I only need the very major rivers. In addition, I am a GIS person, I don't know whether the parameters I chose (e.g. in ArcHydro) are physically meaningful. – tinlyx Oct 21 '14 at 23:05
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    @TingL No problem, DEM stream network extraction is certainly a bit of a 'black art'. The too many rivers issue can be solved by using a higher flow accumulation threshold, but the issue of knowing how to choose a physically meaningful threshold is challenging...see gis.stackexchange.com/questions/115163/… – WhiteboxDev Oct 21 '14 at 23:32
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    And, if you're using ArcGIS spatial analyst. There is a well defined set of steps to do this. On a continental scale the SRTM dataset should give you some reasonable results. You can also define a strahler stream order on the output polylines and subset the data like that. – Neil Ayres Oct 22 '14 at 7:06
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You can download hydrology shapefiles from here for a number of countries around the world. Select your country of choice and Inland water as your subject. You should receive 2 types of shapefiles:

  • A line shapefile depicting line features for rivers, canals and basins
  • A polygon shapefile depicting area features for rivers, canals and basins

I believe there are 5 main countries the Niger River flows through (in order from source to mouth):

  • Guinea
  • Mali
  • Niger
  • Benin
  • Nigeria

Country shapefiles

I find that merging the shapefiles of the same type (ie. all line shapefiles) would be very useful when performing analytics such as querying for specific rivers (ie. the Niger River).

I use QGIS 2.2 and I merge the shapefiles via Vector > Data Management Tools > Merge shapefiles to one:

Merge shapefiles to one

I can then, for fun, do a query (Layer > Query...) for only the Niger River to see what it looks like. The attributes for the shapefiles contain the names of rivers, in this, case I used the following expressions:

"Nam" = 'Niger'

for the merged lines.

"Name" = 'Niger'

for merged areas.

Query

Note that there are small breaks in between certain places but most line features (light blue) connect with the area features (dark blue). Below is the final result of all the rivers in the countries named above using the OpenLayers plugin as the background:

Result

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    it is a good answer but I am unsure if these are "hydrologically correct river-channels" – If you do not know- just GIS Oct 22 '14 at 12:44
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    Ahh, many thanks @usertwoseventwothreenine. Then I completely misunderstood the question! I wasn't sure that the term only focused on DEMs and not on vector shapefiles. – Joseph Oct 22 '14 at 13:02
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    @Joseph Thanks though. That's one of my favorite sources for GIS data. – tinlyx Oct 22 '14 at 14:09
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    Yeah it is still a nice detailed answer that may do the job. – If you do not know- just GIS Oct 22 '14 at 15:07
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    Haha many thanks guys! I'll remember to re-post this answer when someone asks "Are there river shapefiles specifically covering the Niger River in Africa?" :) – Joseph Oct 23 '14 at 11:45
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I have made hydrologically correct river-channels for the Lake Victoria basin. SRTM 90m does a reasonable but imperfect job. For example, I had to adjust numerous regions based on the actual flow of rivers. All is not lost though it sounds as though we can expect the 30m global dataset soon. I would suggest a dry run with 90 m data and then a rerun when the 30 comes out. 30 m for entire Africa would be a challenge but I think it is possible with reasonable computing resources.

To answer your question. YES. Are you aware of this. Very useful dataset and hydro correct.

I would be curious to see how this underused global 30m elevation dataset works. Literature suggest maybe not so great but there is opposing literature.

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  • Thanks for the pointer. I was told 90 m data is more than enough for hydrology, it's good to know that 30 m is better. What software did you use, BTW? I have looked at the ArcHydro-generated?? river network from HydroSHEDS (USGS), and there seems to be no information about river order. – tinlyx Oct 22 '14 at 14:12
  • I used ArcGIS Hydro tools and SAGA GIS in QGIS. The big miss was the 90m data broke a watershed to the east of the lake that I could clearly see a large river crossing (Looks like it passed in a narrow gorge) so I burned low values into SRTM. Did I mention this in my post.... creaf.uab.es/miramon/mmr/examples/miombo/docs/database/hydro30s/… (woops) – If you do not know- just GIS Oct 22 '14 at 14:59
  • updated answer to a hydro correct dataset for africa I forgot about... – If you do not know- just GIS Oct 22 '14 at 15:05
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FAO has this! Look up UN FAO Datasets via geonetwork.

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