Australia: The Land Where Time Began
The Drought that Canít be Seen
A drought of crisis proportions is affecting the Western Hemisphere.
Crops are failing in Central America with millions being in danger of
starving, and according to McNutt if the drought doesnít break soon,
ships passing through the Panama Canal will need to lighten their loads,
which would increase prices for goods transported globally. The
drought-stricken region spans a vast area in the western United States
that is responsible for much of the fruit, vegetables, and beef that is
produced by the US. Water users have turned to tapping groundwater
aquifers as the drought has worsened to make up the deficit for people,
crops, livestock and industry. According to McNutt, re-greening the
landscape and filling the streams, lakes and reservoirs the aquifers
will remain severely depleted even when rain does return. It is this
drought, the underground drought that canít be see, that is enduring and
worrying, and in need of attention.
A global look at the depletion of underground water has been provided by
the Gravity Recovery and climate experiment (GRACE) satellites, by
monitoring small temporal changes in the gravity field of the Earth. It
was confirmed by GRACE that there has been massive losses from the
aquifer that lies beneath the agriculturally important Central Valley
since the 1980s.
Central Valley Groundwater Study: A Powerful New Tool to Assess Water
Resources in California's Central Valley
In the decade between 2003 and 2012, the drawdown was equivalent to the
entire storage volume of Lake Mead, which is the largest surface
reservoir in the US. Wells have run dry which leads to detectable uplift
or rebound of the land due to the displacement of water (see Borsa et
al., p. 1587).
A natural long-term solution to water storage is underground reservoirs.
The expense and environmental issues associated with the building of
dams is avoided by taking advantage of aquifers. Aquifers are not
subject to evaporative loss, which differs from the situation of surface
aquifers, though they are recharged only slowly under natural conditions
as excess precipitation percolates into the aquifer. The average age of
groundwater, in some cases, can be many thousands of years old, dating
back to times of wetter climates. Though at times, when water is
withdrawn at prodigious rates, hydrological processes are not able to
recharge the reservoirs fully, especially where the surface of the
ground is built over with impervious surfaces.
E.g., in the Tucson area, water from the Colorado River is used to
recharge artificially the aquifers with excess water in wet years that
can be tapped later in dry years. It is guaranteed by the statewide 1980
Groundwater Management Act that over a 10-year period the aquifer cannot
be overdrawn. The California legislature, the last state in the west
that doesnít have groundwater regulation, has been prompted by the
current crisis, to pass a series of bills establishing state-level
oversight of pumping from aquifers.
Surface water and groundwater are all part of a single coupled system, and they respond on different time scales to precipitation changes.
|Author: M.H.Monroe Email: firstname.lastname@example.org Sources & Further reading