After a 30-year hiatus, large-scale irrigation projects have returned to the development agenda in sub-Saharan Africa (SSA). However, the magnitude and drivers of past schemes’ performance remains poorly understood. We quantify the performance, measured as the proportion of proposed irrigated area delivered, of 79 irrigation schemes from across SSA 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. We attribute these findings to political and management frameworks underpinning irrigation development in SSA. First, an emphasis on national food security promotes low-value crops, reducing economic viability. Second, proposals are unrealistically large, driven by optimism bias and political incentives. Finally, centralized bureaucracies lack the technical expertise, local knowledge and financial resources to ensure long-term maintenance. Our findings highlight the need for greater learning from past investments’ outcomes if improvements in agricultural productivity and water security across SSA are to be realized.

在中断了30年之后，大型灌溉项目又回到了撒哈拉以南非洲（SSA）的发展议程。但是，对过去方案性能的大小和驱动力仍然知之甚少。通过将规划文件与卫星衍生土地覆盖图上当前计划规模的估计值进行比较，我们对整个SSA中的79个灌溉计划的绩效进行了量化，以建议灌溉面积的比例衡量。我们发现大量证据表明，投资未能实现预期的收益，其中计划支持中位数占提议区域的16％，仅20％（占25％）的计划提供了超过80％的资金，而16％（占20％）的资金完全处于无效状态。在过去的六十年中，性能并未得到改善，我们发现与常见的失败原因（例如计划规模和气候）之间的关系有限。我们将这些发现归因于支持撒哈拉以南非洲灌溉发展的政治和管理框架。首先，对国家粮食安全的重视促进了低价作物的生长，降低了经济生存能力。其次，在乐观偏见和政治激励的推动下，提案规模过大，不切实际。最后，中央官僚机构缺乏技术专长，本地知识和财力，无法确保长期维护。我们的发现强调，要实现整个SSA的农业生产率和水安全状况的改善，就需要从过去的投资结果中吸取更多的教训。由乐观偏见和政治动机驱动。最后，中央官僚机构缺乏技术专长，本地知识和财力，无法确保长期维护。我们的发现强调，要实现整个SSA的农业生产率和水安全状况的改善，就需要从过去的投资结果中吸取更多的教训。由乐观偏见和政治动机驱动。最后，中央官僚机构缺乏技术专长，本地知识和财力，无法确保长期维护。我们的发现强调，要实现整个SSA的农业生产率和水安全状况的改善，就需要从过去的投资结果中吸取更多的教训。