Rivers to the Ocean

Texas Waters, Rivers and the Gulf of Mexico

The Water Cycle - Nature’s Recycling System

• Water is essential for all life on Earth.

• Water occurs as a liquid, a solid, and a gas.

• Water is constantly recycled.

• Most of the water on Earth is in the oceans.

Watersheds feed our water supply

Groundwater(aquifer)

Rain and runoff seep under ground into aquifers.

Surface water(streams, rivers, lakes and ponds)

Rain and emerged spring water run down across the land into streams, rivers, lakes and ponds.

A watershed is an area of land that drains downward into a common area. All land can be divided into watersheds.

Texas Sources of Fresh Water

Surface waterRivers, streams, lakes make up river basins

Groundwater

Over half of Texas’ water needs are met by underground aquifers.

Springs

Springs bubble up to the surface from groundwater.

Spring are often the home of unique plants and animals.

Some rivers start as springs.

Wetlands

Examples of wetlands are freshwater and saltwater marshes, swamps, lagoons, bogs, and playas or prairie potholes. There are even wetlands in the desert.

Wetlands provide habitat, protect water quality, prevent flooding, control sediments, and support aquatic life.

Freshwater Wetland

Coastal Wetland

In Texas, Rivers Flow to the Gulf of Mexico

Rivers provide fresh water to the salty ocean.

The zone where fresh river water mixes with the salty ocean is called an estuary or bay.

A mix of freshwater and saltwater in estuaries is needed to help much of our seafood, saltwater sportfish, crabs and shrimp reproduce and grow.

Blue Crab

Hermit Crab Gulf Shrimp

Nueces Bay

Red Drum

Saltwater in the Gulf

Most of the water on Earth (97%) is salty.

The water that we drink is freshwater. Less than 1% of the Earth’s water is available for drinking.

Saltwater in the Gulf of Mexico is home to a diversity of life.

Rivers: from Source to Coast

Physical Changes:

• Steep slope; flow swiftly

• Narrow and shallow channel

• Bottom of coarse gravel and boulders

• Drains a small area

• Lots of shade; less variation in temperature

Rivers generally begin in low-lying areas at higher elevations and flow downhill within a channel. Along their length, rivers swell in size, gather tributaries and drain an increasingly larger catchment area. Biological changes also occur along the length of a river. Rivers can be divided into three categories based on these physical and biological characteristics: Upper, Middle, and Lower.

Physical Changes:

• Gentle slope; flow reduced

• Channel widens and deepens

• Bottom of small gravel and sand

• Drains a larger area

• River begins to meander

• Little shade; clear water

• Large variation in temperature

Physical Changes:

• Slope and flow further reduced

• Substrate of mud and silt

• Little to no shade; small variation in temperature

• Water is turbid due to sediments

• Delta forms as river deposits sediment

UPPER COURSE

MIDDLE COURSE

LOWER COURSE

Biological Changes:

• Abundant tree canopy

• Few to no aquatic plants

• Inputs from land important as food source (decaying organic matter)

• Lots of aquatic insects

• Cold water fish that eat insects

Biological Changes:

• Less Tree Canopy

• Lots of aquatic plants and algae

• Organic matter from upstream important as food source

• Lots of aquatic insects

• Warm water fish that eat insects and other fish

Biological Changes:

• Little to no tree canopy

• Aquatic plants absent from main channel

• Lots of phytoplankton

• Low diversity of aquatic insects; more mollusks

• Fish largely planktivores