Lesson 1
- Erosion formed the Grand Canyon
- Wind, rain, ice, snow and water can cause erosion
- The water cycle is driven by energy from the sun
- Example of a river system is taking a shower
- A river system is a network of streams and rivers that drain an area of its runoff
- River systems are divided into regions called watersheds
- Another word for watershed is drainage basin
- The largest watershed in the US is the Mississippi River watershed
- Examples of major watersheds are: Columbia River, Rio Grande, and Colorado River watersheds
- Watersheds are separated from each other by an area of higher ground called a divide
- As a stream forms, it erodes soil and rock to make a channel
- When a stream first forms, its channel is usually narrow and steep.
- Usually the stream transports rock and soil downstream and makes the channel wider and deeper
- When streams become longer and wider, they are called rivers.
- A stream’s ability to erode is influenced by 3 factors: gradient, discharge, and load
- Gradient – measure of the change in elevation over a certain distance
- High gradient gives a stream or river more erosive energy to erode rock and soil
- A river or stream that has a low gradient has less energy for erosion
- The amount of water that a stream or river carries in a given amount of time is called discharge
- The discharge of a stream increases when a major storm occurs or when warm weather rapidly melts snow
- As the stream’s discharge increases, its erosive energy and speed and the amount of materials that the stream can carry also increase
- The size of a stream’s load is affected by the stream’s speed
- Fast-moving streams can carry large particles
- William Morris Davis developed a model for stages of river development
- Rivers cause erosion by removing and transporting soil and rock from the riverbed
- The water cycle is the movement of Earth’s water form the ocean to the atmosphere to the land and back to the ocean
- A developing river can be described as youthful, mature, old, or rejuvenated
Lesson 2
- Flowing water erodes the Earth’s surface
- Rock and soil drop, or deposit, their load downstream
- Rock and soil deposited by streams are called sediment
- River and streams deposit sediments where the speed of the water current decreases
- Heavy minerals are sometimes deposited at places in a river where the current slows down (placer deposit)
- A river’s current slows when a river empties into a large body of water, such as a lake or an ocean
- A delta usually forms on a flat surface and is made mostly of mud
- The world’s deltas are home to a rich of plant and animal life
- When a fast-moving mountain stream flows onto a flat plain, the stream slows down very quickly
- As stream slows down, it deposits sediment
- The sediment forms an alluvial fan
- Flood plains are rich farming areas because periodic flooding brings new soil to the land
- One type of barrier that can be built to help control flooding is a dam
Lesson 3
- The water located within the rocks below the Earth’s surface is called groundwater
- Surface water seeps underground into the soil and rock-area is divided into 2 zones
- Rainwater passes through the upper zone, called the zone of aeration
- Farther down, the water collects in an area called the zone of saturation
- The water table rises during wet seasons and falls during dry seasons
- An aquifer can be described by its ability to hold water and its ability to allow water to pass freely through it
- The more open spaces, or pores, between particles in an aquifer, the more water the aquifer can hold
- Porosity is influenced by the differences in sizes of the particles in the rock layer
- A rock that sops the flow of water is impermeable
- Friction is a force that causes moving objects to slow down
- Springs are a natural way that water reaches the surface
- Caves and sinkholes form from the erosion of limestone by groundwater
Lesson 4
- Pollution is the introduction of harmful substances into the environmentWater can become so polluted that it can no longer be used or can even be deadly
- A leak from a sewer pipe is a point-source pollution
- Nonpoint-source pollution is much more difficult to control because it does not come from a single source
- Pollution normally reaches bodies of water by runoff
- Main sources of nonpoint-source pollution are street gutters, fertilizers, eroded soil, and silt from farming and logging, drainage from mines, and salts from irrigation.
- Oxygen dissolved in water is called dissolved oxygen or DO
- Such an increase in water temperature is called thermal pollution
- Nitrates are normally occurring compounds of nitrogen and oxygen
- Alkalinity refers to the water’s ability to neutralize acid
- A pH below 6.0 is too acidic for most aquatic life
- When water reaches a sewage treatment plant, it is cleaned in 2 ways: (1) primary treatment and (2) secondary treatment
- Primary treatment – dirty water is passed through a large screen to catch solid objects, such a paper, rags, and bottle caps
- Water then placed in a large tank, where smaller particles, or sludge, can sink and be filtered out
- Secondary treatment – water is sent to an aeration tank, where it is mixed with oxygen and bacteria
- Bacteria feed on the wastes and use oxygen
- Water then sent to another settling tank, where chlorine is added to disinfect the water
- Water finally released into a water source – a river, lake, or the ocean
- Wastewater flows the house into the tank, where the solids sink to the bottom
- Bacteria break these wastes on the bottom of the tank
- Water flows form the tank into a group of buried popes (drain field)
- Water we use in our homes is not the only way water is used
- More water is used in industry and agriculture than in homes
- Water can be conserved by using only the water that is needed by recycling water, and by using drip irrigation systems