This study presents a new geospatial framework for detecting and mapping ephemeral sand rivers (ESRs) across the West African Sahel, focusing on Burkina Faso, Mali, and Niger, where food security challenges are acute. ESRs, which remain dry most of the year, act as vital subsurface water reservoirs in arid environments. During the wet season, infiltrated streamflow is stored within sandy beds, minimizing evaporative losses and providing shallow groundwater with potential to support domestic, livestock, and agricultural needs during dry periods. The methodology integrates hydrological analyses, remote sensing, and machine learning. A high-resolution drainage network was derived from the 90 m MERIT DEM, based on national reference river networks and satellite-derived information. A Random Forest model predicted river flow intermittency and identified ephemeral rivers (flowing 1–4 months annually, catchment area ≥1000 km²), around which 500 m buffer zones were delineated for analysis. Two composite thresholds (CTs) combining NDESI–NDVI spectral indices achieved moderate accuracy: CT1 (42 %) and CT2 (72 %), with CT2 serving as a first-order tool for sandy riverbed detection. A multi-temporal supervised land use/land cover classification achieved high accuracy (92 %) and F1 scores >0.86, outperforming the spectral thresholds. Using vegetation presence as a proxy for shallow groundwater, 19 % of ESRs (402 km) were identified as areas of potentially accessible water storage near settlements representing about 3 million people (4.8 % of the population) across the three countries. These findings highlight the importance of ESRs for sustainable water management and climate-resilient livelihoods in the Sahel.

Managing natural resources in transboundary river basins is a complex task in which societal needs and environmental impact are intertwined. The nexus paradigm engages with such a challenge by analysing synergies and trade-offs across Water-Energy-Food-Ecosystems (WEFE) sectors. We present a WEFE nexus operationalisation using a participatory modelling approach in the transboundary Lielupe river basin, shared between Latvia and Lithuania. Using a modelling cycle approach, we illustrate a stakeholder-driven pathway from generic and qualitative to increasingly quantitative system tools useful for basin-scale policy analysis. Stakeholders prioritised agricultural nutrient pollution as a critical nexus issue strongly linked to land-use. Three policy alternatives to address this issue were co-identified with stakeholders from both riparian countries: (i) implementing nature-based solutions; (ii) transitioning to organic agriculture; and (iii) promoting arable land-use transitions to former native landscapes. The long-term effect of such policies is explored using a System Dynamics simulation model. Results highlight the importance of promoting active transboundary cooperation for water quality control, as unilateral action hampers the effect of long-term ambitious policies. Even highly ambitious unilateral action can delay the achievement of river basin quality objectives in the order of a decade, a critical finding for the wider Baltic region and the achievement of EU water quality objectives. Based on an exploratory analysis, we found that implementing basin-scale solutions for nutrient control would reduce nitrogen concentration by around 30 % with a 2 % co-benefit of increasing vegetation stocks, yet at the cost of decreasing cereal production by 8 %. This work illustrates the capabilities of a tailor-made simulation model crafted to answer locally relevant policy questions with a nexus perspective in a transboundary river basin. Developing and using a simulation model in a participatory way can explore policy futures while fostering dialogue among riparian stakeholders. This is a promising way to promote cooperation towards solving critical socio-environmental issues in transboundary rivers.

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.

Water conflicts open windows of opportunity for grassroots movements to transform water systems. However, academic fields studying social movements in socio-environmental conflicts are not well equipped to deal with complexity, non-linear dynamics, and emergent properties. Therefore, these fields rarely engage with long-term complex social processes and dynamics leading to systemic socio-technical changes. Researching water conflicts driven by grassroots movements, we ask whether and how the latter can influence a socio-technical transition of a water management regime. Through an emblematic water conflict in Mexico, we analyse the grassroots movement's trajectory since the conflict´s inception by following the dynamic process of developing agency. Our findings show that throughout the conflict, the grassroots movement accumulated and mobilized diverse capitals to initiate water management strategies and practices that catalysed change in the water management regime by stalling the implementation of large infrastructures. Eventually, this led to the inception of a sustainable and just transition.

Problems manifested within social-ecological systems (SES) exhibit dynamic complexity and hold implications for current and future human well-being and environmental sustainability. The complexity of these issues, the ever-present uncertainty inherent to SES, and the multi-stakeholder settings in which they are discussed call for participatory modelling to support decision-making on socio-environmental issues. Yet, this challenging endeavour requires a structured approach — a modelling cycle — to facilitate engagement with the implications of participation and uncertainty as focal points for Good Modelling Practice (GMP). Here we propose an integrated policy analysis framework for SES modelling using System Dynamics (SD). This framework stems from integrating two existing modelling cycles that individually consider participation and uncertainty in SD modelling. Three global modelling phases and a set of tools to address the participation and uncertainty features in SES modelling are distinguished. The framework contributes to mainstreaming GMP, offering a structured model-based approach to enhance the robustness and social acceptance of policies on critical socio-environmental issues.

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.

Open-access remote sensing products provide data for transboundary water management. This study presents a comprehensive overview of the applications, uncertainties and implications of these remote sensing data products in the context of transboundary water management. Focusing on different stages within the transboundary cooperation continuum, we delineate the potential role and application of remote sensing data at the various stages of this cooperation. Despite the uncertainties and capacity requirements for data acquisition, processing and interpretation, we argue that remote sensing broadens opportunities to monitor, assess, forecast, track or validate compliance in transboundary basins, thereby challenging traditional notions of water data exclusivity.

Sentinel-1 observes the whole globe every 12 days (6 days when both satellites were operational) and provides a wealth of data relevant to agriculture. Sugarcane cultivators could potentially benefit from these data by using them to assist operational and management practices. However, first, thorough understanding is needed of Sentinel-1 backscatter and its behavior over sugarcane canopies. In this study, we aimed to improve understanding of how Sentinel-1 backscatter responds to sugarcane yield variability and waterlogging. In order to do so we focused on an irrigated sugarcane plantation in Xinavane, Mozambique. In the analysis presented, we assessed different polarizations, their ratio, and benchmarked them against optical indices and passive microwave observations in different seasons. With the help of a large sugarcane yield dataset, we analyzed how backscatter relates to sucrose yield variability in different seasons. We found VV backscatter related to the stalk development, the most important reservoir for sucrose accumulation. In addition, in a season with reported waterlogging, optical and radar observations showed a delay in sugarcane crop development. Further analysis showed the presence of water underneath the canopy caused an increase in all polarizations and the cross ratio (CR). The results imply that Sentinel-1 backscatter contains information on both waterlogging under the canopy as well as sucrose development in the stalk. By isolating and quantifying the impact of waterlogging on backscatter, it will be possible to further quantify sucrose development with backscatter observations and identify waterlogging simultaneously.

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.

The social-ecological systems (SES) approach elicits a broad understanding of some of the most pressing socionatural challenges (e.g. resource scarcity, biodiversity loss, and climate change) and the responsibility that humans have in addressing them. System dynamics has proven a powerful paradigm for dealing with complex SES-related issues. Here we discuss some ethical considerations of using system dynamics (SD) to model SES, something that is often either overlooked or discussed as an isolated issue. Sustainable development and human rights are used as ethical standpoints across the modelling cycle, opening the discussion around guiding principles that need to be considered when modelling SES. Based on these, a set of guiding ethical questions are identified and classified across a participatory SD modelling cycle. This structured approach is a simple yet potentially useful tool for SD practitioners to examine the ethical implications of their modelling endeavours in the context of grand societal challenges.

Water enables health, education, and economic well-being opportunities for humanity. Access to basic water and sanitation services, freshwater variability, and water storage are some of the dimensions that may impact on human development worldwide. Yet few studies quantitatively explore the relationship between water and human development. This study uses a statistical approach to quantify the Water-Human Development relation in a global sample, both in terms of correlation and causality between variables. Correlation is established using a multiple linear regression approach, while causality is explored by implementing the multi-spatial convergent cross mapping technique. Our study finds strong interdependence between water-related variables and human development globally. Access to water services positively influences the Human Development Index (HDI), seasonal variability of freshwater resources restricts it, and large water storage is not significant. The analysis is robust between 2000 and 2017, and implies that a 1% increment in a country's HDI is associated with a 1.3%–3.2% increment in water and sanitation access. Causal analyses show strong coupling, suggesting positive feedback between access to water services and HDI that could be exploited. Reaching Sustainable Development Goal 6 requires closing the water and sanitation access gaps while addressing freshwater variability challenges. This will result in global human development benefits.

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.

In this study we focus on an irrigated sugarcane plantation in southern Mozambique burdened by waterlogging. We show how Sentinel-1 backscatter and Planet NDVI can be used to monitor sugarcane development. Our results demonstrate Sentinel-1 backscatter is able to monitor sucrose development and, in addition, how waterlogging influences the radar signals in different growth stages. Consequently, we show the potential to monitor sugarcane development and waterlogging simultaneously.

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.