14 March 2011

National Groundwater Awareness Week

What is that thing?
Last week (6 - 12 March) was National Groundwater Awareness Week in the United States.  Did you notice?  Were there lots of events and celebrations in your area, public agencies and private water companies getting out to spread the word, giveaways and picnics (weather-permitting) and frivolity and whatnot in honor of groundwater? Did you tell your neighbors and friends about that newfangled smart-meter on your groundwater well that helps you track your usage?  Did you test the quality of your groundwater sources, track a pollutant plume, call out an illegal dump site?

I didn't think so.  But don't feel so bad about it, I didn't do any of those things either, and groundwater seems to suffer a critical shortage of attention and care these days.  Where I live right now, in the Ozark Mountains of southern Missouri and northern Arkansas, groundwater is one of the most fundamentally valuable natural resources.  So many farms and rural communities depend on natural and abundant groundwater in this region.  Filtered over centuries through ancient limestone and sand-and-gravel aquifers, and recharged by abundant rainfall through vast undeveloped forest and pasture lands, it is some of the cleanest water in the country.  Both hot- and cold-springs are numerous in the area, feeding perennial streams and rivers woven into the very fabric of the ancient landscape.  Compared with where I last lived, among the transplanted palm trees and xeriscaped yards of Tucson AZ, the Ozarks are a veritable rainforest.  This part of the Mid-west remains one of the last remnants of the eastern hardwood habitats found by explorers moving westward from the expanding American colonies in the 18th century, and was still only on the frontier of conflict during the American Civil War.  Outside of the northern Rocky Mountains, this is one of the least developed portions of the country, and the quality of groundwater available here is more-than-adequate representation of environmental quality in the region.

the USGS Active Groundwater Level Network
Groundwater is our most extensive, but most under-appreciated, source of fresh water for domestic, agricultural and industrial uses.  The National Ground Water Association (NGWA) provided a page oriented on awareness for the week, with links to fellow organizations such as The Groundwater Foundation and the Groundwater Protection Council, as well as the federal Environmental Protection Agency (EPA) and the US Geological Survey (USGS).  The USGS operates and gathers data from nearly 1300 wells monitored in real-time, another ~1200 that are measured daily, and still another ~18,000 wells that are inspected by personnel on a regular basis for the nationwide Active Groundwater Level Network.  Archived physical and (less frequent) chemical measurements from these and another ~830,000 groundwater wells across the country are available from the USGS National Water Information System (NWIS) on the web.  The USGS has published hundreds of reports and monographs on groundwater throughout the nation and in the several US protectorate states, and maintains both on-line and print versions of the Groundwater Atlas of the United States with extensive information and map resources.  Despite volcanic bedrock and abundant rainfall, variable interactions between mountains and wind directions make the groundwater contribution to water supplies in Puerto Rico an interesting study on this neglected branch of the water cycle.  For that matter, I hadn't thought much about it, but new US Marine Corps (USMC) studies on the freshwater resources of the mostly-militarized island of Guam in the western Pacific Ocean are just fascinating given such low annual rainfall and highly porous, sand-and-coral soils.

from S.A. Leake, US Geological Survey
But our national groundwater resources have become imperiled by years of neglect, poor awareness in both public and government sectors, singular direction of scientific study, unenforced regulatory compliance, and outright attack by industrial and commercial interests.  All of this water is under our feet, but we still lack the tools to completely define the water volumes available in various aquifers and the rates at which pumped withdrawal can be sustained by natural (precipitation-based) and artificial recharge.  The best we have been able to do are large-scale water budgets, with large uncertainties.  Still, it's a start.  NASA's GRACE mission uses the noise in an otherwise smooth geophysical signal to tell us the change in groundwater mass over time, albeit for coarse regional analyses around the globe.  To its credit, GRACE results were a clarion call to those in northern India who had little knowledge or understanding of just how overdrawn their groundwater aquifers had become in the past several years.  A paper on the observations and analytical results, obvious in highly-sensitive gravimetric observations from space, was published in 2010 [1] and has already led to some level of reform in groundwater use and irrigation practices of the northern Indian agricultural sector.

from S.A. Leake, US Geological Survey
Similar groundwater "mining" goes on here in the US [2], though in smaller areas for which GRACE is not quite as useful yet.  For these, the USGS and local water agencies maintain monitoring wells at which groundwater depth is fastidiously recorded and analyzed across the areas of interest, allowing the detection of trends in recharge or over-pumping.  Some agencies have recently added a tool to their monitoring arsenal: synthetic aperture radar (SAR), mounted on an aircraft or using data from several commercial satellites currently in orbit, can measure surface elevations in minute detail.  By comparing of different SAR images for an area, the interferometric SAR (InSAR) method [3,4] can highlight deformation at the soil surface due to changes in the water content of the underlying geologic formations.  In the US Southwest, major population areas and agricultural regions in California [5], Arizona and Nevada [6] have subsided as much as 2 - 10 meters between approximately 1950 and 2000, the period over which urban and farm development has seen sharp growth in that region.

This is not an exaggeration;
from S.A. Leake, US Geological Survey
There are obvious problems associated with groundwater extraction, including unsustainable pumping and the eventual depletion of uncertain resources, but there remain still-uncertain issues associated with quantity and the influences of drought and floods, climate change in recharge and pumping areas, and unresolved conflict regarding commercial exploitation for the bottled water market.  As well, there are prominent issues of groundwater quality due to industrial and municipal waste disposal, seawater intrusion in over-pumped coastal aquifers, and chemical and nutrient exchange with surface waters.  Even legal issues abound regarding property jurisdiction in the artificial separation of surface and subsurface water and mineral rights, and groundwater is hardly addressed in transboundary agreements over resource sharing between states and countries in international river basins.  Here, I have touched on only a small fraction of the issues surrounding our human dependence on groundwater around the world.  Consider yourself now aware, though still only marginally informed, of the issues.  Hydrogeologists make a whole career out of these issues, with a solid grounding in the Earth sciences including geology and hydrology, to name only the most general of studies.  Since groundwater distributions and their slow flow processes may only remotely conform to the surface topography, aquifer processes remain out-of-sight and out-of-mind for many to whom their sudden disappearance would ultimately and severely affect lives and livelihoods.


[1] Rodell, M., I. Velicogna, and J. Famiglietti, 2009: "Satellite-based estimates of groundwater depletion in India." Nature, v. 460, no. 7258, pp. 999-1002. DOI: 10.1038/nature08238

[2] Galloway, D.L., D.R. Jones, and S.E. Ingebritsen, eds., 1999: "Land subsidence in the United States." US Geological Survey, Circular 1182, 175 pp. Available in html and djvu.

[3] Galloway, D.L., D.R. Jones, and S.E. Ingebritsen, 2000: "Measuring land subsidence from space." US Geological Survey, Fact Sheet 051-00. Available in html and pdf.

[4] Bawden, G.W., M. Sneed, S.V. Stork, and D.L. Galloway, 2003: "Measuring human-induced land subsidence from space." US Geological Survey, Fact Sheet 069-03. Available in html and pdf.

[5] Galloway, D.L., K.W. Hudnut, S.E. Ingebritsen, S.P. Phillips, G. Peltzer, F. Rogez, and P.A. Rosen, 1998: "Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California." Water Resources Research, v. 34, no. 10, pp. 2573 - 2585. DOI: 10.1029/98WR01285

[6] Amelung, F., D.L. Galloway, J.W. Bell, H.A. Zebker, and R.J. Laczniak, 1999: "Sensing the ups and downs of Las Vegas - InSAR reveals structural control of land subsidence and aquifer-system deformation." Geology, v. 27, pp. 483 - 486. DOI: 10.1130/0091-7613(1999)​027<0483:STUADO>​2.3.CO;2


Michael E said...

Thanks, Matthew. A very informative post!

M. Garcia said...

Author's Note: this post was a tweeted selection for the Waterwired TGIF on 25 March 2011.