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Current Fresh Water “Mass Balance”

Water Demand– Resident Population (2003): 150 thousand

– Visitors: 1 million per year Similar yearly demand as about 20 thousand resident Assuming ~2 weeks average stay per visitor

Water Supply– 80% drinking water from ground water

– North: 180 wells, 35 Mgal/d Nearly all wells in North Primarily limestone aquifer

– South: Surface runoff, 9.9 Mgal/d Surface water runoff over weathered volcanic rock Occurs locally only after intense rain (high permeability)

“Supply Adequate to Meet Current Needs” (2003 Estimates) – Supply ~ 45 Mgal/d

– Demand (proportional to population) ~ 170 thousand

– Provides an estimate of average “consumption rate”

Source:U.S. Geological Survey (USGS)http://pubs.usgs.gov/wri/wri034126/

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Change in Climate Variables

Temperature– Current: Mean–26oC; High–30oC; Low–24oC– Warming Rate: < 2 degree Celsius per 20 years– Projected: 2010–26oC; 2015–27oC; 2030–29oC

Rainfall– Current Annual Mean: 96 in (2.4 m) / yr– Current Annual Range: 85-115 in / yr– Current: 70% in Jul-Dec; 12% from Typhoons– Mean Change till 2030: Marginal (<0.1m); Uncertain– Change in Typhoons: Marginal; Uncertain

Source:U.S. Global Change Research Program: The Pacific Assessmenthttp://www2.eastwestcenter.org/climate/assessment/climate_draft2a.html

Source:U.S. Geological Survey (USGS)http://pubs.usgs.gov/wri/wri034126/

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Projected Fresh Water “Mass Balance”

Water Demand– Population 2010: 180K (200K) Water: ~ 53 Mgal/d

– Population 2015: 225K (245K) Water: ~ 65 Mgal/d

– Population 2030: 250K (270K) Water: ~ 72 Mgal/d

Water Supply– Wells: Current = 35 Mgal/d

The current yield is about 50% of sustainable yield Sustainable yield: 70 Mgal/d

– Surface runoff: Current = 9.9 Mgal/d Limited projected change under climate change Occurs locally only after intense rain (high permeability)

Potential Shortfalls: None till 2030 – Total sustainable supply: 79.9 Mgal/d

– Estimated demand in 2030: 72 Mgal/d

Source:Western Pacific Institute of Guamhttp://www.weriguam.org/v2/projects_ground.php

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Conclusions

Population change dominates climate change in water supply-demand equation (at least till 2030)

Now till 2030: No anticipated freshwater shortfall; 2030 is about “break-even”

Beyond 2030: Surge in population could cause water scarcity; Climate change impacts still secondary

Beyond 2030: The warming rate could cause slight increase in demand beyond 2050

Large uncertainties for climate change impacts on typhoons; Some uncertainty for non-typhoon rainfall

Change in temperature appears too small for impacts on energy usage

Change in rainfall appears small enough not to impact operations in US DOD facilities

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Recommendations / Guidance

Climate change is not a major concern for freshwater, especially in the next few decades

Population growth may need to be carefully monitored to ensure sustainable freshwater through 2030

Beyond 2030, new ways to generate freshwater may be required

Climate change effects on freshwater may be felt more towards the latter half of the century

Climate change may exacerbate potential water scarcity caused by population

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Related studies

Conclusion agree with related studies Morel, A. and B. Morel (2006): From Global Warming to

Water Scarcity: What Are the Most Urgent Environmental Problems of the Region. Report of the Discussion Group on Environmental Security, NATO Security through Science Series, 103-107.

Vorosmarty, C.J., Green, P., Salisbury, J., and R.B. Lammers (2000): Global Water Resources: Vulnerability from Climate Change and Population Growth. Science, 289 (5477): 284-288.