hsbalangay 1
SAINT LOUIS UNIVERSITY
SCHOOL OF NATURAL SCIENCES
Department of Biology
SAINT LOUIS UNIVERSITY
SCHOOL OF NURSING, ALLIED HEALTH,
AND BIOLOGICAL SCIENCES
Department of Biology
MODULE 2
ENVIRONMENTAL ISSUES AND PROBLEMS
UNIT 3
Problems of the Hydrosphere
The hydrosphere is the total amount of water on the planet. The hydrosphere includes water
that is on the surface of the planet, underground, and in the air.
A. Water Resource
A planet's hydrosphere can be liquid, vapor, or ice. On Earth, surface water is found in
lakes, rivers, streams, wetlands, and watersheds. As streams flow downhill, they combine with
other streams and form rivers. The more streams that run into a river, the larger the river
becomes. As streams and rivers move across the land, they form a flowing network of water
called a rivers system. The area of land that is drained by a river is known as a watershed.
The frozen part of Earth's hydrosphere is made of ice: glaciers, ice caps and icebergs. The
frozen part of the hydrosphere has its own name, the cryosphere. Water moves through the
hydrosphere in a cycle. Water collects in clouds, then falls to Earth in the form of rain or snow.
This water collects in rivers, lakes, and oceans. Then it evaporates into the atmosphere to start
the cycle all over again. This is called the water cycle.
Groundwater is the water stored beneath the Earth’s surface in sediment and rock
formation. As water travels beneath the Earth’s surface, it eventually reaches a level where
the rocks and soil are saturated with water. This level is known as the water table. In wet regions,
the water table may be at the Earth’s surface and a spring of fresh water may flow out onto
the ground. But in deserts, the water table may be hundreds of meters beneath the Earth’s
surface. The water table is actually not as level as its name implies. The water table has peaks
and valleys that match the shape of the land above it. Just as surface water flows downhill,
groundwater tends to flow slowly from the peaks of the water table to the valleys.
An underground formation that contains groundwater is called an aquifer. The water
table forms the upper boundary of an aquifer. Most aquifers consist of materials such as rock,
sand, and gravel that have a lot of spaces where water can accumulate. These aquifers hold
water in much the same way that a sponge holds water. Groundwater can also dissolve rock
formations, such as those made of limestone, and fill vast caves with water, which creates
underground lakes. Aquifers are an important water source for many cities and for agriculture.
To reach an aquifer, surface water must travel down through permeable layers of soil and
rock. Water cannot reach an aquifer from places where the aquifer is covered by
impermeable materials.
The area of the Earth’s surface where water percolates down into the aquifer is called
the recharge zone. Recharge zones are environmentally sensitive areas because any pollution
in the recharge zone can also enter the aquifer. The size of an aquifer’s recharge zone is
affected by the permeability of the surface above the aquifer. Structures such as buildings
