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

Mutema, Macdex; Jewitt, Graham; Chivenge, Pauline; Kusangaya, Samuel; Chaplot, Vincent

doi:10.1016/j.pce.2015.10.001

Cited by 7 publications

(7 citation statements)

References 36 publications

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“…6), plot-scale runoff response generally exceeded watershed-scale discharge response. In agreement with this, Mutema et al (2015), a study in South Africa, observed a significant reduction in unit runoff as plot size increased from micro-plots (1 m 2 ) to plots (10 m 2 ) and subsequently to mico-catchments (0.23 km 2 ). Similarly, van de Giesen et al (2011) reported that runoff decreased with increases in plot size.…”

Section: Plot Runoff and Outlet Dischargesupporting

confidence: 66%

Effects of a deep-rooted crop and soil amended with charcoal on spatial and temporal runoff patterns in a degrading tropical highland watershed

Bayabil

Tebebu

Stoof

et al. 2016

Hydrol. Earth Syst. Sci.

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Abstract. Placement and hence performance of many soil and water conservation structures in tropical highlands has proven to be challenging due to uncertainty of the actual location of runoff-generating areas in the landscape. This is the case especially in the (sub-)humid areas of the Ethiopian highlands, resulting in limited success of such conservation measures. To improve understanding of the effect of land use on spatial and temporal runoff patterns in the Ethiopian highlands, we monitored runoff volumes from 24 runoff plots constructed in the 113 ha Anjeni watershed, where historical data of rainfall and stream discharge were available. In addition, we assessed the effectiveness of charcoal amendment of the soil and crop rooting depth in reducing runoff, and we compared the effect of lupine (a deep-rooted crop) to that of barley. We also measured daily rainfall, surface runoff, and root zone moisture contents during the monsoon seasons of 2012 and 2013 (with all plots being tilled in 2012, but only barley plots tilled in 2013). In addition, we analyzed longterm surface runoff from four plots, and outlet discharge data from the research site (1989)(1990)(1991)(1992)(1993) were analyzed and compared with our observations. Results showed that the degrees of soil degradation and soil disturbance (tillage) were significant factors affecting plot-scale runoff responses. As expected, runoff was greater from more degraded soils. Overall, under the commonly applied lupine cropping practice, runoff was higher than under the commonly applied barley cropping practice. In particular, considerable difference was observed during smaller rainfall events (approximately < 20 mm) in 2013, when lupine plots (non-tilled) had greater runoff than barley plots (tilled). Charcoal tended to decrease runoff, but results were not significant.

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Section: Plot Runoff and Outlet Dischargesupporting

confidence: 66%

Effects of a deep-rooted crop and soil amended with charcoal on spatial and temporal runoff patterns in a degrading tropical highland watershed

Bayabil

Tebebu

Stoof

et al. 2016

Hydrol. Earth Syst. Sci.

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“…Table ; Figure ). These findings are concordant with studies where slope gradient was identified as the main driver of runoff generation at a global scale (Chaplot et al, ; Mutema et al, ; Mhazo et al, ; Prosdocimi et al, ). Notably, measured soil organic matter (i.e., SOC and N content and stocks) correlated positively to unit‐area runoff, but negatively to soil losses, implying greater runoff with low detachment and sediment transportation.…”

Section: Discussionsupporting

confidence: 90%

Assessment of soil erosion under rainfed sugarcane in KwaZulu‐Natal, South Africa

Abdalla

Dickey

Hill

et al. 2019

Natural Resources Forum

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Soil erosion from agricultural land use runoff is a major threat to the sustainability of soil composition and water resource integrity. Sugarcane is an important cash and food security crop in South Africa, subjected to an intensive soil erosion, and consequently, severe land degradation. This study aimed to investigate soil erosion and associated soil and cover factors under rainfed sugarcane, in a small catchment, KwaZulu‐Natal, South Africa. Three replicated runoff plots were installed at different slope positions (down, mid and upslope) within cultivated sugarcane fields to monitor soil erosion during the 2016–2017 rainy season. On average, annual runoff (RF) was significantly greater from 10 m2 plots with 1163.77 ± 2.63 l/m/year compared to 1 m2 plots. However, sediment concentration (SC) was significantly lower in 10 m2 (0.34 ± 0.04 g/l) compared to 1 m2 (6.94 ± 0.24 g/l) plots. The annual soil losses (SL) calculated from 12 rainfall events was 58.36 ± 0.77 and 8.84 ± 0.20 t/ha from 1 m2 and 10 m2 plots, respectively. The 1 m2 plot, SL (2.4 ± 1.41 ton/ha/year) in the upslope experienced 33% more loss than the midslope and 50% more loss than the downslope position. SL was relatively lower from the 10 m2 plots than the 1 m2 plots, which is explained by high sediment deposition at the greater plot scale. SL was negatively correlated with the soil organic carbon stocks (r = −0.82) and soil surface cover (r = −0.55). RF decreased with the increase of slope gradient (r = −0.88) and soil infiltration rate (r = −0.87). There were considerable soil losses from cultivated sugarcane fields with low organic matter. These findings suggest that to mitigate soil erosion, soil organic carbon stocks and vegetation cover needs to be increased through appropriate land management practices, particularly in cultivated areas with steep gradients.

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“…The changes of average q (in l m ‐2 day ‐1 ) and SL (in g m ‐2 day ‐1 ) fluxes with contributing area were described in greater detail by Mutema et al . (). The q decreased by 24% between microplot and plot scale, followed by a steeper 76% decrease from plot to microcatchment scale (Table ) and further decrease in a downstream direction, by 4.3 fold from microcatchment to subcatchment, and by over 99% from subcatchment to catchment level.…”

Section: Resultsmentioning

confidence: 97%

“…Negative correlations at microcatchment scale could be indicative of increased C‐rich baseflow into streamflow. Past studies reported high baseflow contribution to streamflow at this outlet (Chaplot and Ribolzi, ; Mutema et al ., ). Once the dissolved C joins the open streamflow system, it mineralizes rapidly but the relatively stable particulate C remains in transit and that explains positive correlations at subcatchment and other downstream outlets.…”

Section: Discussionmentioning

confidence: 97%

“…runoff plots (microplots: 1 × 1 m 2 and plots: 2 × 5 m 2 ) and nested catchments (microcatchment: 0.23 km 2 ; subcatchment: 1.20 km 2 ; catchment: 9.75 km 2 ; sub‐basin: 253 km 2 ; basin: 29 038 km 2 ), used in this study, was described in detail by Mutema et al . (). The microcatchment is an overgrazed hillslope (Dlamini et al ., ; Mchunu et al ., ) at Potshini, 10 km west of Bergville town.…”

Section: Methodsmentioning

confidence: 97%

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Changes in carbon and nutrient fluxes from headwaters to ocean in a mountainous temperate to subtropical basin

Mutema

Chivenge

Nivet

et al. 2017

Earth Surf Processes Landf

Self Cite

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Water erosion provides major links in global cycles of carbon (C), nitrogen (N) and phosphorus (P). Although significant research on erosion mechanisms has been done, there is still little knowledge on C, N and P fluxes across landscapes to the ocean and their controlling factors in subtropical climates. A four-year study quantifying and comparing particulate and dissolved C, N and P from multiple scales (microplot, plot, microcatchment, subcatchment, catchment, sub-basin and basin) was performed in Thukela basin (≈30 000 km 2 ), South Africa. The basin climate was largely subtropical-humid [mean annual precipitation (MAP) > 980 mm yr -1 ], but temperate (MAP >2000 mm yr -1 ) on the highlands. Open grassland, cropland and bushland were the major land uses. On average, 65, 24 and 4 g m -2 yr -1 C, N and P were displaced from original topsoil positions, but only 0.33, 0.005 and 0.002 mg m -2 yr -1 were, respectively, exported to the ocean. The fluxes decreased by 95, 97 and 84%, respectively, from plot to microcatchment outlet; and decreased further in downstream direction by >99% from microcatchment to basin outlet. The hillslope (microplot to microcatchment) fluxes correlated strongly with rainfall parameters. Particulate contributions dominated hillslope fluxes at 73, 81 and 76% of total annual C, N and P, respectively. Although particulate C dominated in the microcatchmentcatchment reach (55%), N (54%) and P (69%) were dominated by dissolved forms. The lower basin zone was dominated by dissolved flux contributions at 93, 81 and 78% for C, N and P for the sub-basin outlet. These results suggested spatially varying drivers of C, N and P losses from the landscape to the ocean, via the river network. Deposition was envisaged the dominant hillslope level loss process, which gradually gave way to mineralization and biotic uptake in the river network as flux contributions shifted from being predominantly particulate to dissolved forms.

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

Abstract: International audienc

Cited by 7 publications

References 36 publications

Effects of a deep-rooted crop and soil amended with charcoal on spatial and temporal runoff patterns in a degrading tropical highland watershed

Effects of a deep-rooted crop and soil amended with charcoal on spatial and temporal runoff patterns in a degrading tropical highland watershed

Assessment of soil erosion under rainfed sugarcane in KwaZulu‐Natal, South Africa

Changes in carbon and nutrient fluxes from headwaters to ocean in a mountainous temperate to subtropical basin

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