Blue and Green Water Resource Management under Climate Change

Freshwater on land can be understood as two linked reservoirs: blue water, which comprises surface and groundwater flows accessible for human use, and green water, which refers to soil moisture and evapotranspiration that sustain terrestrial ecosystems and rainfed agriculture. Under a warming climate, shifts in precipitation patterns, rising temperatures and land-use change alter the balance between these reservoirs, exacerbating water scarcity and ecosystem stress. Effective management therefore requires a holistic view that integrates water accounting, predictive modelling and adaptive policy. Recent advances combine observational networks, remote sensing and process-based models to map blue and green water distribution, quantify their sensitivity to climatic extremes, and explore trade-offs between agricultural productivity, environmental flow needs and urban demand. Emerging strategies promote conjunctive use of surface and soil moisture, investment in soil health to enhance green water storage, and flexible allocation rules that reflect the changing fluxes. A global perspective on blue and green water underpins more resilient water-management frameworks capable of withstanding hydrological uncertainty and safeguarding both livelihoods and ecosystems.

Research from Nature Portfolio

Recent studies have refined continental-scale partitioning of evapotranspiration into green and blue components by integrating energy-balance and water-balance remote-sensing products at fine spatial resolution. These efforts reveal that roughly 70 per cent of evapotranspiration across temperate landscapes derives from green water, with pronounced regional contrasts in irrigated zones where blue water supports supplemental crop water use. Time-series analyses over two decades demonstrate declining reliance on blue water in some areas in response to conservation measures, while central plains intensify consumptive blue water use under warmer, drier summers. Such insights provide a critical baseline for tracking the efficacy of water-management interventions and for calibrating process models under novel climate regimes.

Blue and Green Water Resource Management under Climate Change publication trend

The graph below shows the total number of articles in blue and green water resource management under climate change across all publications each year (not limited to Nature Index journals).

Technical terms

Blue water: The portion of freshwater in rivers, lakes and aquifers available for abstraction and human use.

Green water: Soil moisture and water transpired or evaporated by vegetation, vital for rainfed agriculture and natural habitats.

Evapotranspiration: The combined loss of water to the atmosphere through plant transpiration and soil evaporation.

References

1. Global patterns in water flux partitioning: Irrigated and rainfed agriculture drives asymmetrical flux to vegetation over runoff. One Earth (2023).
2. Partitioning Evapotranspiration into Green and Blue Water Sources in the Conterminous United States. Scientific Reports (2017).
3. Agricultural Water Productivity-Based Hydro-Economic Modeling for Optimal Crop Pattern and Water Resources Planning in the Zarrine River Basin, Iran, in the Wake of Climate Change. Sustainability (2018).
4. Impacts of Climate and Land-Use Change on Blue and Green Water: A Case Study of the Upper Ganjiang River Basin, China. Water (2020).