About 70% of the worlds population dwells in coastal zones. With
the economic and population growth, the shortage in freshwater supply
becomes increasingly acute. With surface water more and more depleted and
polluted, coastal communities have turned to groundwater to make up for the
shortfall. For domestic supply purposes, the percentage of groundwater use
has increased to more than 40% on a worldwide basis.
Hydraulic conductivity is the most important property of geological formations as the
flow of fluids and movement of solutes depend on it. Among fluids, water and
contaminant migration beneath, the ground surface have become critical for water
resource development, agriculture, site restoration and waste disposal strategies.
Effective prediction of transport of chemical pollutants through a subsurface groundwater
system and associated assessments of risk requires a valid “conceptual model” of the
contaminant migration scenario. The classical contaminant conceptual model is one of a near-
surface “leachable source zone” where chemical contaminant is leached, i.e.
dissolved/solubilised, into water infiltrating through the source (Figure 4.2).
Mining wastes can cause significant ecological destruction.
Often, solid mine wastes are dumped into streams,
destroying habitat and causing siltation and heavy metal
and other contamination. Even when such wastes are
stored out of water channels, trace materials can leach into
surface waters and infiltrate into local groundwater. Fine-
grained tailings can wash into local waterways and degrade
streams by covering and filling coarser-grained substrates.
In addition to the creation of more wastewater, urban areas
add to poor water quality in a number of ways. The high
concentration of impervious surfaces increases runoff from
roads and can carry numerous pollutants such as oils,
heavy metals, rubber, and other automobile pollution into
waterways and streams. The reduction in water percolation
into the ground can also affect the quantity and quality
of groundwater. Stormwater runoff in urban areas can
overwhelm combined stormwater and wastewater treatment
systems when high volume flows exceed treatment