Sources and export of nutrients in the Zambezi River basin: status and future trend

Tang, T. ORCID: https://orcid.org/0000-0002-2867-9241, Strokal, M., Wada, Y. ORCID: https://orcid.org/0000-0003-4770-2539, Burek, P. ORCID: https://orcid.org/0000-0001-6390-8487, Kroeze, C., van Vliet, M., & Langan, S. ORCID: https://orcid.org/0000-0003-0742-3658 (2018). Sources and export of nutrients in the Zambezi River basin: status and future trend. In: International Conference Water Science for Impact, 16-18 October 2018, Wageningen, Netherlands.

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Abstract

In the past decades, nutrient enrichment in African water bodies has been frequently reported and associated to long-term ecological and socio-economic consequences, such as species extinction, unsafe drinking water and compromised local livelihood. Meanwhile, rapid population growth and land-use change towards intensified food production are projected in Africa. As a result, substantial increases are expected in human-induced nutrient inputs (e.g. human waste and fertilizer) to the terrestrial and aquatic environments. This may potentially further deteriorate African water bodies.
As part of the Integrated Solution for Water, Land and Energy (IS-WEL) project, this study aims to assess the status and projected changes of nutrient sources, inputs to rivers and export to seas, shading light on possible solutions to minimize further nutrient-induced deterioration of the water bodies and maximize the availability of water of suitable quality for different sectors. This study focuses on the Zambezi river basin, the fourth largest transboundary basin draining through eight southern African countries. Nutrient sources, inputs to rivers and export to sea are estimated using the MARINA model (Model to Assess River Inputs of Nutrients to seAs) under current conditions and future climate, land use and socio-economic projections up to 2050.
Results show that for the current period (2005-2010), inputs of nutrients (nitrogen and phosphorus) to rivers and their export to sea are mainly attributed to natural sources. These sources include nitrogen fixation by the natural ecosystems, phosphorus weathering, and leaching of organic nitrogen and phosphorus from non-agricultural areas. By 2050, nutrient sources will be at least doubled due to anthropogenic inputs in the basin. Consequently, the fraction of human-induced nutrient export are projected to increase considerably, especially for dissolved inorganic phosphorus from domestic wastewater. Additionally, nutrient export to sea is strongly influenced by the intra- and inter-annual precipitation and discharge variabilities in the region. The study highlights the need to simultaneously consider source control, infrastructure development and climate adaptation to minimize further nutrient-induced deterioration of water bodies.

Item Type:	Conference or Workshop Item (Paper)
Research Programs:	Water (WAT)
Depositing User:	Luke Kirwan
Date Deposited:	22 Oct 2018 10:07
Last Modified:	27 Aug 2021 17:30
URI:	https://pure.iiasa.ac.at/15543

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