Earth's Hydrosphere

TEKS 7.8A & 7.8C: Into Science Grade 7

Learning Goal:

Model the effects of human activity on groundwater and surface water, and analyze catastrophic events like floods and hurricanes.

1. Understanding Watersheds (TEKS 7.8C)

A watershed (or drainage basin) is an area of land where all water drains to a single point. Gravity is the force that moves this water.

The Bathtub Analogy:

Think of a watershed like a bathtub. The high edges of the tub are the 'Divides' (mountains/ridges). No matter where a drop lands inside the tub, gravity pulls it down to the drain (the main river).

  • Divide: The high ridge that separates watersheds.
  • Tributaries: Smaller streams that flow into a larger river.
  • Runoff: Water flowing over the surface (not soaking in).
Watershed Diagram

A Divide is the high ground that separates two different watersheds.

2. Groundwater & Aquifers

Water doesn't just sit on top of the ground; it soaks in (infiltration) to be stored underground.

The Sponge Analogy:

An aquifer isn't an underground lake. It is rock that acts like a wet sponge. The water is trapped in tiny holes (pores) inside the rock.

  • Permeability: How easily water flows through rock. (Gravel = High, Clay = Low).
  • Porosity: The amount of empty space (holes) in the rock.
  • Water Table: The top line of the groundwater. It drops during droughts.
  • Subsidence: When we pump water out too fast, the ground can sink or collapse.
Aquifer Diagram

Groundwater is stored in the Zone of Saturation.

3. Human Impact & Pollution

Humans change how water moves and how clean it is.

  • Point Source Pollution: Comes from ONE specific spot (e.g., a factory pipe). Easy to trace.
  • Non-Point Source: Comes from MANY scattered sources (e.g., oil from cars, fertilizer from lawns). Hard to trace.
  • Urbanization: Building cities adds concrete (impermeable). This stops infiltration and increases flooding.
  • Eutrophication: Fertilizer runoff causes algae blooms -> algae dies -> bacteria eat it -> oxygen is used up -> fish die.
Pollution Sources

Urbanization (concrete) increases runoff and flooding.

4. Catastrophic Events (TEKS 7.8A)

Natural events in the hydrosphere can reshape the land.

Hurricanes: Massive storms formed over warm ocean water. They cause damage via high winds and storm surge (flooding).

Floods: The most common hazard. High volume of water overflows banks.

Drought: Extended period of little rain. Lowers the water table and kills vegetation.

5. Watch & Learn

What is a Watershed?

A clear, animated explanation of how land shape directs water flow.

Groundwater, Aquifers, and Wells

Visualize what is happening underground in the 'hidden' hydrosphere.

Point vs. Non-Point Source Pollution

Learn how to identify where pollution comes from.