Mapping irrigation potential from renewable groundwater in Africa – a quantitative hydrological approach

Hydrology and Earth System Sciences

Y.Altchenko¹  K. G.Villholth¹ 

DOI  :  10.5194/hess-19-1055-2015

学科分类：地球科学(综合)

来源: Copernicus Publications

【 摘 要 】

Groundwater provides an important buffer to climate variability in Africa.Yet, groundwater irrigation contributes only a relatively small share ofcultivated land, approximately 1% (about 2 × 10⁶ hectares)as compared to 14% in Asia. While groundwater is over-exploited forirrigation in many parts in Asia, previous assessments indicate anunderutilized potential in parts of Africa. As opposed to previouscountry-based estimates, this paper derives a continent-wide, distributed(0.5° spatial resolution) map of groundwater irrigation potential,indicated in terms of fractions of cropland potentially irrigable withrenewable groundwater. The method builds on an annual groundwater balanceapproach using 41 years of hydrological data, allocating only that fractionof groundwater recharge that is in excess after satisfying other presenthuman needs and environmental requirements, while disregardingsocio-economic and physical constraints in access to the resource. Due tohigh uncertainty of groundwater environmental needs, three scenarios,leaving 30, 50 and 70% of recharge for the environment, were implemented.Current dominating crops and cropping rotations and associated irrigationrequirements in a zonal approach were applied in order to convert rechargeexcess to potential irrigated cropland. Results show an inhomogeneouslydistributed groundwater irrigation potential across the continent, evenwithin individual countries, mainly reflecting recharge patterns andpresence or absence of cultivated cropland. Results further show thataverage annual renewable groundwater availability for irrigation ranges from 692 to1644 km³ depending on scenario. The total area of cropland irrigablewith renewable groundwater ranges from 44.6 to 105.3 × 10⁶ ha,corresponding to 20.5 to 48.6% of the cropland over the continent. Inparticular, significant potential exists in the semi-arid Sahel and easternAfrican regions which could support poverty alleviation if developedsustainably and equitably. The map is a first assessment that needs to be complimentedwith assessment of other factors, e.g. hydrogeological conditions,groundwater accessibility, soils, and socio-economic factors as well as morelocal assessments.

【 授权许可】

Unknown