Page 411 - Environment: The Science Behind the Stories

Groundwater
springs feed
river water

Freshwater wetlands
Salt marsh
Pesticides and
fertilizer enter
groundwater
and surface
water
Agricultural pollutants
and eroded soil
Levees facilitate shipping but
prevent deposition of river
sediments to coastal wetlands
River
Water withdrawals for
irrigation reduce river flow

Dam
Reservoir
Urban and
industrial Ocean
pollutants
Dam blocks river flows and
traps sediments in reservoir
Groundwater flowing
into river and ocean
Figure 15.3 Water flows through freshwater systems and marine and coastal aquatic systems that
interact extensively with one another. People affect the components of the system by constructing dams
and levees, withdrawing water for human use, and introducing pollutants. Because the systems are closely
connected, these impacts can cascade through the system and cause effects far from where they originated.

Aquifer recharge
area

Artesian
well
Well

Water
table
Spring
Ground-
water
Figure 15.4 Groundwater may
occur in unconfined aquifers
above impermeable layers or in
confined aquifers under pressure
between impermeable layers.
Water may rise naturally to the surface
Unconfined Confined Upper Lower at springs and through the wells we
aquifer aquifer confining confining dig. Artesian wells tap into confined
410 layer (clay) layer (clay) aquifers to mine water under pressure.

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