From Plans to Pipelines: Unpacking the Impact of Irrigation Infrastructure in Tanzania Using Novel Counterfactuals

Beyond its direct impacts on agricultural productivity, irrigation infrastructure is used by policy makers to achieve other objectives like food security, job creation, and ,more broadly, poverty reductionHowever, the evidence required by policy makers while formulating national irrigation plans is often not adequately available due to two reasons. First, irrigation’s causal impact is hard to isolate due to endogeneity in infrastructure placement. While econometric methods address this, they do not fully resolve the issue. Second, and more importantly, national level evidence on the causal impacts of irrigation is hard to come by. This is especially true in African countries, where the impacts of irrigation are not as extensively documented as they are in other parts of the global south. This study addresses the above gaps in the literature by developing a novel empirical framework that integrates a national sample censushousehold survey, community-level irrigation access, and administrative records on irrigation infrastructure to evaluate the impact of irrigation schemes in Tanzania. Specifically, we assess impacts on agricultural productivity, production costs, livestock holdings, poverty indicators, and food consumption. Beyond its empirical contributions, this study introduces a methodological innovation to compare villages with and without irrigation schemes while addressing endogeneity concerns. Rather than focusing solely on geographic and engineering determinants of irrigation placement, we incorporate socioeconomic and political-economy factors alongside hydrological and agroecological considerations—an approach never applied in previous studies to the best of our knowledge. We combine the 2020 National Sample Census of Agriculture with a national irrigation database that classifies schemes by hydrological feasibility and political priority. Using geospatial identifiers, census communities are matched to irrigation schemes, and we implement two increasingly stringent definitions of potential control communities to verify the robustness of our causal estimates. Our treatment identification strategy employs propensity score matching at the village level, followed by regression analyses of household-level outcomes. By integrating political-economy, agropolitical economyecological, and hydrological factors, this study provides a more complete and accurate understanding of irrigation’s role in agricultural and economic resilience. Finally, this study provides timely evidence on the implications of public irrigation investment by providing valuable evidence during a period of renewed interest in expanding irrigation infrastructure by the Government of Tanzania. Over the past two years, the Government of Tanzania has made substantial financial commitments to enhance irrigation infrastructure nationwide. These efforts are part of a broader strategy to implement the provisions of the National Irrigation Master Plan (National Irrigation Commission, 2022). As such, there is renewed interest among policymakers in Tanzania in understanding the broader impacts of public investments in irrigation infrastructure.