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Changing water availability during the African maize-growing season, 1979-2010

Changing water availability during the African maize-growing season, 1979-2010
Changing water availability during the African maize-growing season, 1979-2010

Understanding how global change is impacting African agriculture requires a full physical accounting of water supply and demand, but accurate, gridded data on key drivers (e.g., humidity) are generally unavailable. We used a new bias-corrected meteorological dataset to analyze changes in precipitation (supply), potential evapotranspiration (Ep, demand), and water availability (expressed as the ratio P/Ep) in 20 countries (focusing on their maize-growing regions and seasons), between 1979 and 2010, and the factors driving changes in Ep. Maizegrowing areas in Southern Africa, particularly South Africa, benefitted from increased water availability due in large part to demand declines driven primarily by declining net radiation, increasing vapor pressure, and falling temperatures (with no effect from changing windspeed), with smaller increases in supply. Sahelian zone countries in West Africa, as well as Ethiopia in East Africa, had strong increases in availability driven primarily by rainfall rebounding from the long-term Sahelian droughts, with little change or small reductions in demand. However, intraseasonal supply variability generally increased in West and East Africa. Across all three regions, declining net radiation contributed downwards pressure on demand, generally over-riding upwards pressure caused by increasing temperatures, the regional effects of which were largest in East Africa. A small number of countries, mostly in or near East Africa (Tanzania and Malawi) experienced declines in water availability primarily due to decreased rainfall, but exacerbated by increasing demand. Much of the reduced water availability in East Africa occurred during the more sensitive middle part of the maize-growing season, suggesting negative consequences for maize production.

maize, sub-Saharan Africa, trends, water demand, water supply
1748-9326
Estes, Lyndon D.
6301c89d-4567-48ba-9808-8c9dae3fcc99
Chaney, Nathaniel W.
bc3ca362-9e26-46af-bd26-f99983445106
Herrera-Estrada, Julio
81b87fc8-5a36-4622-8a55-eef06e9c9485
Sheffield, Justin
dd66575b-a4dc-4190-ad95-df2d6aaaaa6b
Caylor, Kelly K.
9495817c-5392-47ed-a013-1d02f501aa28
Wood, Eric F.
ee59ebb9-367e-48ce-beab-22666be5095d
Estes, Lyndon D.
6301c89d-4567-48ba-9808-8c9dae3fcc99
Chaney, Nathaniel W.
bc3ca362-9e26-46af-bd26-f99983445106
Herrera-Estrada, Julio
81b87fc8-5a36-4622-8a55-eef06e9c9485
Sheffield, Justin
dd66575b-a4dc-4190-ad95-df2d6aaaaa6b
Caylor, Kelly K.
9495817c-5392-47ed-a013-1d02f501aa28
Wood, Eric F.
ee59ebb9-367e-48ce-beab-22666be5095d

Estes, Lyndon D., Chaney, Nathaniel W., Herrera-Estrada, Julio, Sheffield, Justin, Caylor, Kelly K. and Wood, Eric F. (2014) Changing water availability during the African maize-growing season, 1979-2010. Environmental Research Letters, 9 (7), [075005]. (doi:10.1088/1748-9326/9/7/075005).

Record type: Review

Abstract

Understanding how global change is impacting African agriculture requires a full physical accounting of water supply and demand, but accurate, gridded data on key drivers (e.g., humidity) are generally unavailable. We used a new bias-corrected meteorological dataset to analyze changes in precipitation (supply), potential evapotranspiration (Ep, demand), and water availability (expressed as the ratio P/Ep) in 20 countries (focusing on their maize-growing regions and seasons), between 1979 and 2010, and the factors driving changes in Ep. Maizegrowing areas in Southern Africa, particularly South Africa, benefitted from increased water availability due in large part to demand declines driven primarily by declining net radiation, increasing vapor pressure, and falling temperatures (with no effect from changing windspeed), with smaller increases in supply. Sahelian zone countries in West Africa, as well as Ethiopia in East Africa, had strong increases in availability driven primarily by rainfall rebounding from the long-term Sahelian droughts, with little change or small reductions in demand. However, intraseasonal supply variability generally increased in West and East Africa. Across all three regions, declining net radiation contributed downwards pressure on demand, generally over-riding upwards pressure caused by increasing temperatures, the regional effects of which were largest in East Africa. A small number of countries, mostly in or near East Africa (Tanzania and Malawi) experienced declines in water availability primarily due to decreased rainfall, but exacerbated by increasing demand. Much of the reduced water availability in East Africa occurred during the more sensitive middle part of the maize-growing season, suggesting negative consequences for maize production.

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More information

Accepted/In Press date: 12 June 2014
Published date: 11 July 2014
Keywords: maize, sub-Saharan Africa, trends, water demand, water supply

Identifiers

Local EPrints ID: 479268
URI: http://eprints.soton.ac.uk/id/eprint/479268
ISSN: 1748-9326
PURE UUID: 196db523-9240-4cc5-81c9-e9f651758892
ORCID for Justin Sheffield: ORCID iD orcid.org/0000-0003-2400-0630

Catalogue record

Date deposited: 20 Jul 2023 16:51
Last modified: 06 Jun 2024 01:54

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Contributors

Author: Lyndon D. Estes
Author: Nathaniel W. Chaney
Author: Julio Herrera-Estrada
Author: Kelly K. Caylor
Author: Eric F. Wood

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