Application of environmental magnetism to estimate source contribution by lithology to Kruger National Park reservoirs

Abstract

Sediment source fingerprinting using environmental magnetism has successfully differentiated between sediment sources in several studies in the Eastern Cape Province of South Africa. The method was applied in this study to the near-natural landscape of southern Kruger National Park (Mpumalanga Province) to trace sediment and determine sediment yields by lithology in four reservoir catchments that were underlain by igneous, metamorphic, and sedimentary rocks. The Park area has no history of cultivation and is a conservation area, so catchment sources were dominated by underlying lithologies. One sediment core was collected in the assumed deepest area of the reservoir. Source discrimination and apportionment were estimated using a common statistical protocol that includes a Mann-Whitney U or Kruskal-Wallis H test, mass conservation test, discriminant function analysis, and an (un)mixing model. A contribution from each lithology-defined source was estimated.Sediment yield by lithology was estimated by using published catchment areaspecific sediment yields in combination with the (un)mixing model. Underlying lithology determined vegetation type and density, and vegetation appeared to play a crucial role in protecting soils and reducing erosion. Proximity to reservoir, that is, travel distance for eroded sediment, and connectivity were also important factors controlling the relative contribution from each potential source. The contributing area for sediment was found to be dynamic through time and was probably dependent on runoff and temporal variations in vegetation cover.

Understanding sediment in river systems—Building on a 50‐year contribution

“…Three papers in this Special Issue are devoted specifically to fingerprinting techniques. Firstly, Miller et al (2022) have used environmental magnetism to differentiate successfully sediment sources by lithology in areas underlain by igneous, metamorphic, and sedimentary rocks in the near-natural landscape of southern Kruger National Park (Mpumalanga Province), South Africa.…”

“…Three papers in this Special Issue are devoted specifically to fingerprinting techniques. Firstly, Miller et al (2022) have used environmental magnetism to differentiate successfully sediment sources by lithology in areas underlain by igneous, metamorphic, and sedimentary rocks in the near‐natural landscape of southern Kruger National Park (Mpumalanga Province), South Africa. Secondly, Lake et al (2022), in an investigation based on both laboratory and field study, suggest that particle‐size distributions, whilst often crucial to ensuring the comparability of source and target sediment samples in fingerprinting studies, may of themselves offer a cheaper and more easily applied fingerprint method than many of the properties more traditionally applied for this purpose.…”

Propagation characteristics of the flow and suspended sediment peaks in the three gorges reservoir, China: Insight from numerical simulations and measured data

“…Reservoirs offer diverse benefits to humankind, that is, power generation, flood control, navigation and irrigation (Li et al, 2021; Miller et al, 2022). However, their overall effectiveness is severely affected by sedimentation which encroaches available storage space and poses threats to the aquatic ecosystem (Cooper et al, 2018).…”