Waterpans as climate change adaptation infrastructure in East African ASALs

Waterpans are shallow man-made structures used to harvest rainwater. They are becoming an increasingly important source of water for domestic use, livestock production, and wildlife in the arid and semi-arid lands (ASALs) of East Africa. As governments expand the construction of thousands of new waterpans for climate adaptation, the ecological, public health, and governance dimensions of these systems are poorly characterised and largely absent from national policy frameworks. This special session features seven linked contributions from the Sustainable Waterpans project (funded by the Water and Development Partnership Programme - the Netherlands) providing the most comprehensive multidisciplinary assessment of waterpan systems to date across twelve waterpans in Narok County, Kenya, spanning contrasting land uses and wet and dry seasons.

The first contribution examines the physicochemical and microbiological water quality and finds that Escherichia coli was detected in all waterpans and exceeded WHO and Kenyan drinking-water standards in 100% of samples, with waterpan land use or season explained greater variation than identity. Geogenic fluoride levels were above safe limits in >50% of all samples, representing an additional chemically distinct and management-resistant hazard. The second contribution characterizes risks of zoonotic pathogen transmission using a One Health framework and shows that shared use by humans, livestock and wildlife provides many routes for faecal contamination and disease transmission. The third and fourth contributions review GHG dynamics, indicating waterpans as robust net sources of methane and carbon dioxide, in both seasons, with fluxes considerably higher than the adjacent savannah - results that have direct implications for savannah carbon budgets and national climate inventories. The fifth contribution deals with the metacommunity structure of phytoplankton and zooplankton, showing that season was the main structuring factor for both guilds: Assemblages were compositionally more heterogeneous among waterpans in the dry season, while the wet-to-dry transition produced the highest temporal community turnover. Toxin-producing cyanobacteria, including Microcystis aeruginosa and Anabaena flos-aquae, dominated across all land-use types and seasons, indicating a persistent microcystin contamination risk, while environmental filtering, principally temperature, ammonium, waterpan area, and dissolved oxygen concentration, outweighed spatial isolation as the primary metacommunity assembly driver. The sixth contribution characterizes benthic macroinvertebrate communities as bioindicators of ecological condition, examining how land use, water quality, and seasonal hydroperiod variability shape assemblage structure and biotic integrity. The seventh contribution presents a systematic review of the policy and regulatory landscape governing waterpan construction and management in Kenya, identifies critical gaps between the current national framework and the available evidence base, and proposes an integrated management framework linking water safety, biodiversity, GHG accountability, and community governance.

Together, these contributions demonstrate that waterpans are indispensable but under-managed infrastructure at the intersection of water security, public health, biodiversity, and climate. We propose the adoption of nature-based solutions, including livestock exclusion fencing and riparian vegetation restoration, that can offer practical, low-cost pathways to simultaneously reduce contamination, harmful algal blooms, and GHG emissions. Realizing their full potential as climate-adaptive infrastructure requires site-specific, seasonally adaptive, and community-based management strategies, underpinned by coordinated action across water, health, environment, and climate policy sectors.