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Aqueduct's future projections provide critical insights into how water availability and risk may change due to climate change, population growth, and economic development. This tutorial explains the methodology behind these projections and how you can use them to inform your decisions.

 

Data and Methodology

Aqueduct's future projections cover key indicators like water supply, water use, water stress, water depletion, and variability. These projections are based on the HYPFLOWSCI6 dataset (Sutanudjaja et al. 2023), which utilizes climate forcing data from multiple future scenarios run through five different climate models. 

 

Socioeconomic and Climate Scenarios (SSPs/RCPs)

The projections are developed for three distinct scenarios used in CMIP6:

  • SSP1-RCP2.6 (Optimistic): Represents a future with limited global temperature rise (1.3°C to 2.4°C by 2100) due to sustainable socioeconomic growth, strong environmental regulations, and rapid technological advancements.
  • SSP3-RCP7.0 (Business as Usual): A middle-of-the-road scenario with moderate temperature increases (2.8°C to 4.6°C by 2100) characterized by regional competition, inequality, and slower progress on environmental issues.

  • SSP5-RCP8.5 (Pessimistic): A high-emission scenario with significant temperature increases (3.3°C to 5.7°C by 2100) driven by fossil-fuel-based development and limited global environmental concern.

     

Important Note on Scenario Interpretation: 

It's crucial to understand that these scenarios represent distinct policy and development pathways, not "best-case" and "worst-case" outcomes. For example, the "optimistic" scenario (SSP1-RCP2.6), while positive in terms of climate change mitigation, might show higher water stress in some regions compared to a "pessimistic" scenario. This can happen because the "optimistic" scenario often assumes increased economic activity and development, which in turn can lead to higher water demand, even if the impacts of climate change on water availability are less severe. Therefore, when comparing scenarios, consider the complex interplay of socioeconomic development, technological change, and climate impacts on water resources.

General Circulation Models (GCMs) and Handling Uncertainty

To account for uncertainties inherent in climate modeling, Aqueduct uses multiple GCMs for each scenario. Specifically, five GCMs (GFDL-ESM4, IPSL-CM6A-LR, MPI-ESM1-2-HR, MRI-ESM2-0, and UKESM1-0-LL) were used for each scenario. These GCMs were chosen to represent a range of temperature and precipitation variations. By using multiple GCMs, Aqueduct captures a wider range of possible future climate conditions and acknowledges the inherent uncertainties in climate projections. The median of the five GCMs is displayed for each scenario, providing a central estimate while still acknowledging the spread of potential outcomes. This approach allows users to see the range of possibilities and understand the level of confidence in the projections.

 

Data Processing

The model data undergoes spatial and temporal aggregation to be used in Aqueduct's indicator calculations. Spatial aggregation is done at the HydroBASINS Level 6 sub-basin level. Temporal aggregation smooths the data using a 10-year trailing moving average and isolates the trend using Theil-Sen regression for the following timeframes:

  • 2030: 2015-2045
  • 2050: 2035-2065

  • 2080: 2065-2095

     

Bias Correction

To account for potential deviations between historical GCM climate forcing data and actual observed data, a bias correction is applied to the future projections. This adjustment ensures the projections are more aligned with observed baseline data.

 

Limitations

  • Irrigation Data: Crop extent data is only projected to 2050. Post-2050 irrigation demand may be underestimated in some regions.

  • Livestock Water Demand: Livestock water demand data is held constant after 2014, potentially underestimating future demand.

     

Interpreting the Data on the Water Risk Atlas tool

  • Absolute Value: The absolute value shown on the map represents the median projected score or volume from the five GCMs for the chosen scenario and timeframe.

  • Timeframes: Each year displayed (2030, 2050, 2080) represents a 30-year trend centered on that year.

     

Using Future Projections in Your Decisions

Aqueduct's future projections can be used to:

  • Assess long-term water risks: Identify regions that may face increased water stress or scarcity in the future.
  • Develop adaptation strategies: Plan for potential changes in water availability and develop strategies to mitigate negative impacts.
  • Make informed investment decisions: Evaluate the long-term viability of projects and investments considering future water risks.
  • Understand scenario implications: Explore how different socioeconomic and climate scenarios might affect water resources in specific regions.

By understanding the methodology and limitations of Aqueduct's future projections, you can effectively incorporate this information into your decision-making processes related to water resource management.