Current Fresh Water “Mass Balance”

1. 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/ Overview_kpt_0730

2. 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. Geological Survey (USGS) http://pubs.usgs.gov/wri/wri034126/ Source: U.S. Global Change Research Program: The Pacific Assessment http://www2.eastwestcenter.org/climate/assessment/climate_draft2a.html Overview_kpt_0730

3. 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 Guam http://www.weriguam.org/v2/projects_ground.php Overview_kpt_0730

4. 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 Overview_kpt_0730

5. 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 Overview_kpt_0730

6. 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. Overview_kpt_0730