Sustainable Water Management - Sustainable Practices in Geoenvironmental Engineering - page 77

runoffs will end up in receiving waters—lakes, rivers, oceans, etc. In the case of managed
runoffs, there are at least two options for the runoffs before they meet the receiving waters:
(1) treatment (full or partial) of the runoff water and (2) no treatment before discharge into
receiving waters. The result of untreated runoffs into receiving waters is obvious—deg-
radation of the quality of the receiving waters. When such occurs, the receiving waters
will require treatment to reach drinking water quality standards. A point can be reached
where the accumulated contaminants will be at a level where treatment of the degraded
receiving water will not be effective—not from an economic standpoint and not from a
regulatory point of view.
The combination of iniltration, and runoffs as potential carriers of contaminants into
the ground and receiving waters (including groundwater) is a prospect that should alert
one to the need for proper management of the sources of contamination of water resources.
Treatment of water to achieve levels of quality dictated by drinking water standards is only
one means for water resource management. The other has to be directed toward eliminat-
ing or mitigating the sources of contamination of water resources.
3.2.2 Harvesting of Groundwater
We have seen in Chapter 1, and in Figures 1.9 and 3.1, that only about 5% of the water in
the world is freshwater. The rest is seawater. This tells us that our drinkable freshwater
resource is severely limited. The graphic in Figure 3.1 informs one that although ground-
water represents about 30% of the available freshwater, at least 90% of the world's popula-
tion rely on this as a source of freshwater (Boswinkel, 2000; WRI et al., 1998). Iniltration
and runoffs carrying contaminants serve as chemical stressors whose impacts on the solid
land environment are both soil contamination and contamination of groundwater . The subject
of soil contamination has been discussed in Chapter 2, and the processes and geoenviron-
mental engineering practices for mitigation and remediation of contaminated soils will be
discussed in Chapters 9 through 11. Groundwater abstraction for drinking water purposes
will require treatment aids. Since reliance on groundwater as a drinking water source is
considerable, it is clear that maintaining acceptable groundwater quality is a high prior-
ity not only because of the need for treatment after abstraction, but also because once the
aquifer is contaminated, clean-up of the aquifer to acceptable standards is almost impos-
sible. When aquifers become contaminated, one key element for aquifer sustainability is
lost. In effect, sustainability of that aquifer as a water resource is lost.
Depletion of aquifers is also another sustainability loss that requires attention. Deple-
tion occurs when the rainfall is insuficient and/or aquifer recharge is exceedingly slow,
i.e., input or replenishment of the aquifer is less than the output. Continued water use from
that aquifer is thus not sustainable. This is occurring with more frequency as water use
has increased by a factor of 6 since the beginning of the twentieth century. The amount
of groundwater abstraction is estimated to be between 950 and 1000 in 2000 km 3 /yea r,
representing about 25% of global water use, which increased from 100 to 150 km 3 /yea r
in 1950—(Howard, 2004). According to the UN, an increase in the world's population of
80 million people per year increases freshwater demand by 64 billion m 3 /year (WWDR,
2012). The Ogallala aquifer in central United States was used at 140% above its recharge
rate (Gleick, 1993), but since 1985, water table levels have stabilized and in some cases have
risen through better water management (High Plains Underground Water Conservation
Di st r ict, 2014).
Freshwater is depleting rapidly in countries such as India, China, and even in the United
States, rivers are drying up and water table levels are decreasing. In China, there is a lack