In northern Australia’s highly seasonal river systems, dry-season waterholes function as critical natural infrastructure. For much of the year they are the only standing freshwater within otherwise intermittent river channels, supporting pastoral operations, regional communities, and biodiversity. Yet their long-term variability is not well quantified within water planning frameworks.

This study uses multi-decadal satellite records to track changes in surface water extent in the Gilbert River across successive wet and dry seasons. By analysing how individual waterholes expand following the wet season and contract through the dry season, the work quantifies how strongly dry-season water availability depends on preceding rainfall and flow conditions.

The results show marked year-to-year variability in waterhole size and persistence. In years following below-average wet seasons, some waterholes contract rapidly and reach minimal extent earlier in the dry season. In contrast, high-flow years support substantially greater dry-season water retention. These patterns demonstrate that “permanent” waterholes are not fixed features, but dynamic systems shaped by climate variability.

As northern Australia faces increasing hydro-climatic volatility and growing pressure for water development, understanding this variability becomes central to risk-aware planning. Recognising waterholes as natural infrastructure provides a practical framework for incorporating dry-year risk and climate variability into water allocation and regional development decisions. By improving understanding of how dry-season water availability responds to climatic drivers, this work supports more resilient long-term development in northern Australia.