Performance of large-scale irrigation projects in sub-Saharan Africa

Abstract

After a thirty-year hiatus, large-scale irrigation projects have returned to the development agenda in sub-Saharan Africa (SSA). Yet, the magnitude and drivers of past schemes performance remains poorly understood. We quantify the performance of 79 irrigation schemes from across SSA, measured as the proportion of proposed irrigated area delivered, by comparing planning documents with estimates of current scheme size from satellite-derived land cover maps. We find overwhelming evidence that investments have failed to deliver promised benefits; with schemes supporting a median 16% of proposed area, only 20 (25%) delivering >80%, and 16 (20%) completely inactive. Performance has not improved over six decades, and we find limited relationships with commonly stated causes of failure such as scheme size and climate.

Scenarios of sustainable irrigation expansion in the 21st century

“…In our analysis, a governance indicatordefined as the institutional capacity of countriesemerges as a socioeconomic factor that best explains the current level of sustainable irrigation deployment. Our findings on the importance of governance and institutions as key conditions for the successful deployment of such adaptation options are in line with other findings on indices reflecting adaptive capacity 9 . The two identified predictors, namely the level of governance and the share of rainfed agriculture, are able to explain more than 70% in the current variations in used sustainable irrigation potential across the globe.…”

“…Overcoming socioeconomic constraints to improve adaptation deployment under climate change is a distinct possibility, and in some cases might be a necessity to prevent substantial reductions in agricultural productivity 23 . Our findings highlight that this might be all but easy given the observed evidence of socioeconomic factors limiting the effectiveness of irrigation deployment 9 .…”

“…In contrast, the region with the smallest SIDI in year 2000 is Sub-Saharan Africa (0.05), which indicates that the region is currently using very little of its sustainable irrigation potential. This is because most countries in the region do not yet have the possibility to access water management technologies and benefit from irrigation (i.e., face economic water scarcity 5 ), even though irrigation has long been emphasized as a solution to intensify agricultural production, support rural economic development and enhance resilience to climate variability and change 33,9 . This also relates to the low levels of governance (e.g.…”

“…This also relates to the low levels of governance (e.g. ineffective national bureaucracies), which has hindered large-scale irrigation projects in Sub-Saharan Africa in the past 9 . The projections of the SIDI emphasize the vast potential for improvement in the region.…”

“…Yet, in over 25% of global rain-fed croplands, irrigation is limited by institutional and economic capacity instead of hydrologic constraints, a condition known as agricultural economic water scarcity 5 . In fact, social, political, and economic factors will ultimately influence future irrigation development 9 . Therefore, there is a pressing need to couple biophysical assessments of irrigation expansion potential with socioeconomic projections to identify future target regions for sustainable intensification of agriculture through irrigation expansion.…”