Water resources management (WRM) models have traditionally distributing water based on system capacities, economic efficiency, and demand (Loucks and Van Beek 2017). However, these efficiency-oriented models often fail to address water distribution inequities (Savenije and Van Der Zaag 2002, Hanemann 2005, Garrick et al 2020). As challenges around water scarcity and distribution inequity intensify, the need for models integrating justice principles to ensure fair and equitable resource allocation is evident.

Ideas of morality have long been central to human thought, shaping essential debates about equity and justice in modern political philosophy. Prominent philosophers like John Rawls and Amartya Sen have significantly contributed to these discussions, offering influential frameworks for understanding these concepts (Rawls 1958, Sen 2008). They argue for the inseparability of justice and fairness, that individuals should have not only equal opportunities (justice) but also equal chances to utilize those opportunities (fairness). Equity is thus achieved when justice and fairness are consistently applied to all.

Justice considerations in WRM broadly encompass distributive justice, focusing on fair resource allocation, and procedural justice, emphasizing transparency in decision-making. Water resources equity may concern distribution between upstream and downstream states in a transboundary basin (Zeitoun et al 2014, Yalew et al 2021), rights and access to clean water in communities (Syme et al 1999) or governance issues addressing multi-sectoral water demands, such as irrigation water demands in the agriculture sector (Gross 2014, Neal et al 2014).

Distributive justice addresses the questions of 'what' (what to distribute), 'to whom' (to whom to distribute), and 'how' (how to distribute) of allocation of common pool resources. This aligns with the principle of 'equitable and reasonable use' of water resources outlined in the United Nations Watercourses Convention (United Nations 1997). It is also reflected in the United Nations Sustainable Development Goal 6 (SDG6), which aims to 'Ensure access to water and sanitation for all' (United Nations 2015). Despite some attempts to incorporate equity aspects in water resources assessments (Dore et al 2012), a significant gap remains in effectively integrating justice principles into WRM models. Addressing these challenges requires the operationalization of specific fairness and justice principles within WRM models. By incorporating insights from socio-economic and philosophical theories, such as welfare economics and Rawlsian justice, into water resource assessments, hydro-economic models could be significantly improved to deliver operational and policy alternatives that balance efficiency and equity.@en

Conventional approaches to irrigation development involve large lumpsum investments in big infrastructure that cannot adapt to changing climate and socio-economic conditions. There is an urgent need for alternative ways of investing in smallholder irrigation in Sub-Saharan Africa (SSA) that are adaptive and avoid capital lock-in. Adaptive Investment Pathways (AdIP), inspired by the Dynamic Adaptive Policy Pathways (DAPP) concept, proposes stepwise investments to support smallholder irrigation development. AdIP builds resilience to future shocks through dynamic and flexible investment plans instead of investing in single static solutions. To develop an empirical grounding for operationalizing AdIP, we draw lessons from three case studies representing different stages of irrigation development along shallow sand river aquifers in Kenya and Zimbabwe. We retrospectively analyse the nature of investments at farm and landscape scales, and the type of risks and opportunities that farmers respond to. We find that in face of risks, farmers diversify their livelihoods, make small investments incrementally especially in response to opportunities and risks created by external triggers, and pause or reorient activity when they reach saturation points, i.e., biophysical or socio-political limits to their development objective, here irrigation development. Governments and external agencies can support smallholder irrigation development in SSA through targeted landscape scale investments that address saturation points faced by smallholders. This requires a robust participatory monitoring framework to identify and respond to saturation points, and a re-thinking of financing mechanisms which do not measure progress against a fixed schedule of investments, but instead measure continuous progress towards the development objective.

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There is an urgent need in sub-Saharan Africa (SSA) to enhance irrigation access to meet the challenges of growing population and climate risk. To achieve this, big investments are currently planned in large irrigation infrastructure. We believe there is danger in following this conventional approach, which requires big lumpsum investments, locking large capital into projects that do not adapt to deep uncertainties from climatic or socio-political factors. Instead, in this Perspective article, we propose an alternate “adaptive investment pathways” (AdIP) approach for planning step-wise investments towards desired objectives, implemented progressively depending on how the future unfolds, in order to gain flexibility. AdIP extends the adaptation pathways concept, which refers to a sequence of actions to be taken in response to a changing reality, and applies it to the context of development under uncertainty. Monitoring and learning is at the heart of this approach, which ensures that the plan adapts as new knowledge becomes available. Thus, AdIP internalizes risk and reduces chances of failures. For financial institutions backing development projects, following a pathway of smaller de-centralized investments lowers risk and incorporates a learning approach that allows re-thinking and adapting along the path. We illustrate the AdIP approach using the case of ephemeral sand river based small-scale irrigation in the drylands of SSA. We conclude that in face of deep uncertainties, the path to successful irrigation development in SSA requires a shift from making few large upfront investments in large-scale projects to making large numbers of smaller investments that assure flexibility.

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In Zimbabwe, farmer-led irrigation is far more widespread than planners and policy makers realise. Along the Shashani sand river, in the arid to semi-arid lands of south-western Zimbabwe, diverse farmer-initiated irrigation ventures exist. This qualitative case study focuses on bucket irrigation, in which very small vegetable fields of up to 450 m² are fenced by tree branches, and irrigated with water from scoop holes in sandy river beds. Farmers initiate and operate their fields with no external assistance. This study presents the benefits of bucket irrigation as an often-overlooked form of farmer-led irrigation development. Through this qualitative and strongly observational study, 26 bucket irrigation farmers and 4 non-irrigators were interviewed using semi-structured interviews where farmers’ perceptions and experiences were captured. We investigate what drives and sustains bucket irrigation, its significance to rural livelihoods under harsh economic and climatic conditions, and the barriers towards scaling this type of farmer-led irrigation development. The results show that drivers for bucket irrigation stem from economic hardship and are gendered. Women are motivated to irrigate mainly by the need to produce vegetables for household consumption, whereas men pursue irrigation due to a lack of employment. Bucket irrigators experience enhanced food security, and have more secure income, contributing to improved wellbeing. Furthermore, despite the desire to scale, the farm size is mainly constrained by fencing and energy for transporting water, which is a result of a persistent lack of financial capital to invest in irrigation technologies. We conclude that bucket irrigation acts as an important livelihood strategy, and that it significantly enhances farmers’ resilience to economic and climatic shocks. Bucket irrigation should not be overlooked in policies that advocate scaling of irrigation. Bucket irrigators have the potential to expand and benefit significantly if supported with innovative financial mechanisms that enable investments in the required technology and knowledge.

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Farmer-led irrigation is valued for its resilience and ability to cope with shocks and benefit from opportunities. Yet, typologies of farmer-led irrigation are mostly static categorisations without analysing farmers’ decision-making over time, and without studying ‘failed’ cases. We therefore analysed temporal changes in farmers’ irrigation strategies to expand, downscale or cease practices as part of wider livelihood decisions and aspirations. This longitudinal study presents irrigation trajectories of 32 farmers in the arid lands of two contrasting socioeconomic settings in Kenya and Zimbabwe. Data were collected through multiple rounds of surveys and in-depth interviews. Results show that farmers frequently alternated strategies or ceased or restarted operations over the years, both by force and choice. Although many farmers were able to start, expand or sustain irrigation, not all managed or aspired to remain engaged in irrigated farming, even if the enabling environment was conducive for market-oriented irrigation development. We therefore conclude that farmers’ needs cannot always be expressed in general terms of growth or commercial farming, nor can they always be satisfied by improving the enabling environment, which may be based on static ontologies of diverse types of farmers.

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In the semi-arid lands of southern Kenya, a dynamic process of farmer-led irrigation has developed over the past two decades. It is characterised by short-term agreements to access land and water. Resident and migrant farmers, capital providers and local landowners have engaged in diverse partnerships to benefit from water and land along the Olkeriai sand river. This study aims to unravel which actors and motives drive the resulting highly dynamic forms of irrigation. Surveys, in-depth interviews and mapping exercises with farmers, capital providers and landowners were conducted over a period of 1.5-years. The results show that involved actors favour short-term lease and partnership arrangements and farmers frequently change fields along the river or leave the area and return. It is primarily the migrant farmers and capital providers who take decisions on when and where to move. They are informed by their experience with production factors, financial gains and losses, partner relations, or the ability to expand. We conclude that individualisation of land rights, migration, abundance of water, proximate markets, and rural-urban networks are instrumental to the emergence of this dynamic form of agriculture. Farmers have found a degree of security in flexibility, to access land and water in shifting fields and partners, rather than in property rights for specific plots. Yet, the short-term scope of these operations for monetary gains raises concerns about the sustainable use of land and water resources in the region.

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Irrigation is commonly viewed as an activity fixed in time and place requiring permanent infrastructure. However, smallholder farmers in Sub-Saharan Africa engage in irrigation in diverse locations under different organizational modalities. This research analyses a flexible and dynamic form of irrigation driven by unique partnerships between migrants and local actors who derive benefits from land and water resources along a sand river. The case study of the ephemeral Olkeriai sand river in Kajiado, Kenya, was based on a baseline survey of 107 farm plots and 23 in-depth interviews with farmers. We found that 75% of the farm plots were managed under transient farming partnerships between migrant farmers and capital providers, locally known as tajiris, who leased land from local landowners to grow high-value market crops. These partnerships are based on flexible agreements between the actors and the frequent need to review and re-build them creates a fertile ground for new entrepreneurial players from within and outside the area, playing a key role in accelerating irrigation intensification and expansion. However, these irrigation ventures are not always successful. Unreliable partners, unstable market channels and increasing costs of irrigation inputs frequently result in farm losses and breaking up of partnership ventures. Furthermore, the lack of collective action among various resource users at the catchment level raises questions on how to sustainably manage the natural resources in sand rivers.

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