Rainfall variability, wetland persistence, and water-carbon cycle coupling in the Upper Zambezi River Basin in Southern Africa

Lauren E.L. Lowman, Tiffany M. Wei, Ana P. Barros

Research output: Contribution to journalArticlepeer-review

Abstract

The Upper Zambezi River Basin (UZRB) delineates a complex region of topographic, soil and rainfall gradients between the Congo rainforest and the Kalahari Desert. Satellite imagery shows permanent wetlands in low-lying convergence zones where surface-groundwater interactions are vigorous. A dynamic wetland classification based on MODIS Nadir BRDF-Adjusted Reflectance is developed to capture the inter-annual and seasonal changes in areal extent due to groundwater redistribution and rainfall variability. Simulations of the coupled water-carbon cycles of seasonal wetlands show nearly double rates of carbon uptake as compared to dry areas, at increasingly lower water-use efficiencies as the dry season progresses. Thus, wetland extent and persistence into the dry season is key to the UZRB's carbon sink and water budget. Whereas groundwater recharge governs the expansion of wetlands in the rainy season under large-scale forcing, wetland persistence in April-June (wet-dry transition months) is tied to daily morning fog and clouds, and by afternoon land-atmosphere interactions (isolated convection). Rainfall suppression in July-September results from colder temperatures, weaker regional circulations, and reduced instability in the lower troposphere, shutting offmoisture recycling in the dry season despite high evapotranspiration rates. The co-organization of precipitation and wetlands reflects land-atmosphere interactions that determine wetland seasonal persistence, and the coupled water and carbon cycles.

Original languageEnglish (US)
Article number692
JournalRemote Sensing
Volume10
Issue number5
DOIs
StatePublished - May 1 2018
Externally publishedYes

Keywords

  • Dynamic wetlands
  • Gross primary productivity
  • Rainfall gradients
  • Spectral reflectance
  • Upper Zambezi River Basin

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

Fingerprint Dive into the research topics of 'Rainfall variability, wetland persistence, and water-carbon cycle coupling in the Upper Zambezi River Basin in Southern Africa'. Together they form a unique fingerprint.

Cite this