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October 2014

Climate Change and Groundwater

Posted: October 10th, 2014


Last week, SPU presented at the annual forum of the National Groundwater Protection Council, a non-profit focused on protecting the nation’s groundwater supplies. The presentation focused on the groundwater aspects of the water resources chapter of the 2014 National Climate Assessment.


When people think about climate change and water they usually think about surface waters – rivers, lakes, etc. Groundwater doesn’t quite get the same level of attention. Reflecting that dynamic, the NCA notes that “…precise responses of groundwater storage and flow to climate change are not well understood nor readily generalizeable…”; in other words, we don’t know a lot about the climate impacts on groundwater.


But groundwater is the primary source of supply in some parts of the U.S. and can play a critical “backup” source of supply when surface supplies are temporarily depleted due to drought. Researchers like Jay Famiglietti at the Jet Propulsion Laboratory are helping to augment our knowledge about groundwater by doing interesting work using satellites to monitor groundwater. A recent study of his looked at groundwater use in CA during the ongoing drought and notes ominously that “…most of the major aquifers in the world’s and arid and semi-arid regions are being depleted at a rapid pace…”


While the NCA highlights some of the uncertainties around groundwater and climate change, it does an excellent job of exploring the interrelationship between precipitation, evapotranspiration, soil moisture and other factors on groundwater recharge, as well as highlighting how groundwater use varies across the country and by different sectors. It also notes the role that groundwater can play as in enabling adaptation, by augmenting groundwater during “wet” periods via infiltration basins and injection wells and utilizing more conjunctive use strategies.


Here in the central Puget Sound, we derive most of our supply from surface water surfaces. An 2008 study by the Central Puget Sound Water Suppliers Forum indicates that 65% of the supply for the three county region is provided by surface water surfaces, with groundwater providing the remaining 35%, mostly in the central and eastern portions of King and Pierce County. Tacoma Public Utilities is a great example of an agency that has successfully integrated the management and use of surface and groundwater supplies.


SPU’s Climate Resiliency Group is committed to tracking and understanding how climate change will affect Seattle’s and the region’s water resources.


– PF




National Groundwater Protection Council
National Climate Assessment (NCA)
NCA Water Resources Chapter
NASA GRACE Satellite
Central Puget Sound Water Supply Forum (CPSWSF)
CPSWSF Existing Municipal Water Supply and Demand Outlook
SPU Climate Change Program