The hydrology of sand rivers in Zimbabwe and the use of remote sensing to assess their level of saturation

S.C. Mpala, A.S. Gagnon, M.G. Mansell, S.W. Hussey

Research output: Contribution to journalArticle

Abstract

Sand rivers are ephemeral watercourses containing sand that are occasionally flooded with rainwater runoff during the rainy season. Although the riverbed appears dry for most of the year, there is perennial groundwater flow within the sand. This water flowing beneath the surface is a valuable resource for local communities; nonetheless our understanding of such river systems is limited. Hence, this paper aims to improve our understanding of the hydrology of sand rivers and to examine the potential use of remote sensing to detect the presence of water in the sand. The relationship between rainfall events and changes in the water level of two sand rivers in the Matabeleland South Province of Zimbabwe was investigated. A lagged relationship was observed for the Manzamnyama River but for the Shashani River the relationship was seen only when considering cumulative rainfall events. The comparison of the modelled flow as simulated by a water balance model with observations revealed the important influence of the effective sediment depth on the recharge and recession of the alluvial channels in addition to the length of the channel. The possibility of detecting water in the alluvial sands was investigated using remote sensing. During the wet season, optical images showed that the presence of water on the riverbed was associated with a smooth signal, as it tends to reflect the incident radiation. A chronological analysis of radar images for different months of the year demonstrates that it is possible to detect the presence of water in the sand rivers. These results are a first step towards the development of a methodology that would aim to use remote sensing to help reducing survey costs by guiding exploratory activities to areas showing signs of water abstraction potential.
Original languageEnglish
Pages (from-to)24-36
Number of pages13
JournalPhysics and Chemistry of the Earth
Volume93
Early online date10 Mar 2016
DOIs
Publication statusE-pub ahead of print - 10 Mar 2016

Fingerprint

Zimbabwe
hydrology
Hydrology
rivers
sands
remote sensing
Remote sensing
Sand
Rivers
saturation
sand
Water
river
water
Rain
water balance
recession
rainfall
Groundwater flow
incident radiation

Keywords

  • Advanced synthetic aperture radar
  • Alluvial aquifer
  • Remote sensing
  • Sand river
  • Water level
  • Zimbabwe

Cite this

Mpala, S.C. ; Gagnon, A.S. ; Mansell, M.G. ; Hussey, S.W. / The hydrology of sand rivers in Zimbabwe and the use of remote sensing to assess their level of saturation. In: Physics and Chemistry of the Earth. 2016 ; Vol. 93. pp. 24-36.
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The hydrology of sand rivers in Zimbabwe and the use of remote sensing to assess their level of saturation. / Mpala, S.C.; Gagnon, A.S.; Mansell, M.G.; Hussey, S.W.

In: Physics and Chemistry of the Earth, Vol. 93, 10.03.2016, p. 24-36.

Research output: Contribution to journalArticle

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