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Spatial scale impact on daily surface water and sediment fluxes in Thukela river, South Africa

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Relation http://oar.icrisat.org/9125/
http://dx.doi.org/10.1016/j.pce.2015.10.001
10.1016/j.pce.2015.10.001
 
Title Spatial scale impact on daily surface water and sediment fluxes in Thukela river, South Africa
 
Creator Mutema, M
Jewitt, G
Chivenge, P
Kusangaya, S
Chaplot, V
 
Subject Others
Agriculture-Farming, Production, Technology, Economics
 
Description The on- and off-site effects of soil erosion in many environments are well known, but there is still limited
understanding of the fluxes in downstream direction due, among other factors, to scarce and poor
quality. A four year study to (i) evaluate water and sediment fluxes at different spatio-temporal scales
and (ii) interpret the results in terms of processes involved and the controlling factors, was conducted in
Thukela basin, South Africa. Five hierarchically nested catchments; namely microcatchment (0.23 km2
),
subcatchment (1.20 km2
), catchment (9.75 km2
), sub-basin (253 km2
) and basin (29,038 km2
), were used
in addition to fifteen (1 m2
) microplots and ten (10 m2
) plots on five locations within the microcatchment.
The results showed 19% decrease of unit-area runoff (q) from 3.1 L m2 day 1 at microplot to
2.5 L m2 day1 at plot scale followed by steeper (56%) decrease at microcatchment scale. The q
decreased in downstream direction to very low level (q 0.26 L m2 day1
). The changes in q were
accompanied by initial 1% increase of soil loss (SL) from 18.8 g m2 day1 at microplot to
19.1 g m2 day1 at plot scale. The SL also decreased sharply (by 39 fold) to 0.50 g m2 day1 at
microcatchment scale, followed by further decrease in downstream direction. The decrease of q with
spatial scale was attributed to infiltration losses, while initial increase of SL signified greater competence
of sheet than splash erosion. The decrease of SL beyond the plot scale was attributed to redistribution of
the soil on the hillslope and deposition on the stream channel upstream of the microcatchment outlet.
Therefore, erosion control strategies focussing on the recovery of vegetation on the slope and stabilisation
of gullies are recommended.
 
Publisher Elsevier
 
Date 2016-04
 
Type Article
PeerReviewed
 
Format application/pdf
 
Language en
 
Rights —
 
Identifier http://oar.icrisat.org/9125/1/56374e1808ae88cf81bd5477.pdf
Mutema, M and Jewitt, G and Chivenge, P and Kusangaya, S and Chaplot, V (2016) Spatial scale impact on daily surface water and sediment fluxes in Thukela river, South Africa. Physics and Chemistry of the Earth, 92. pp. 34-43. ISSN 1474-7065 (In Press)