Surface Water

Chapter 9

Surface water movement: Water (Hydrologic) Cycle

Earths water supply is constantly recycled

The Water Cycle

The Sun provides energy for the water cycle.

Radiation from the Sun causes water to

change to a gas called water vapor.

The process of water vapor changing to a fluid is called condensation.

Precipitation falls to Earth’s surface in the form of rain, snow, sleet, or hail.

Water then flows downslope along Earth’s surface which is called Runoff.

Runoff may reach a stream, river, or lake, may evaporate or may accumulate into puddles and eventually seep into the ground.

Water that seeps into the ground becomes groundwater.For water to enter the ground, there has to

be large pores or spaces in the ground.

Fate of water: Run off or Seep

Certain characteristics will determine whether not water will either seep into or become runoff

1) Vegetation Vegetation allows for loose soil

Loose soil allows water to enter ground

Fate of water

2) Rate of precipitationHeavy:

Water falls too quickly and becomes runoff

Light: allows water to gently slide through

Fate of Water

3) Soil Composition Effects the waters holding capacity Decayed organic matter (humus)

Creates the pores in soil which retains water

MineralsClay – fine mineral which clump together

• Few Spaces

Sand – large pores-allows water to move through it.

Fate of Water

4) SlopesSteep: allows for high runoff & little absorption

Little: low runoff and high absorption

Formation of Stream systemsPrecipitation that does not enter the

ground usually runs off the surface quickly.Surface water flows in thin sheets and

eventually collects in small channelsRunoff increases, channels widen and

become deeper and longerChannels fill up again each time with rainChannel can become a stream

Streams

Some streams flow into lakes and oceans.

Tributaries flow into other streams.

Streams

A large stream = River. All of it’s tributaries make up a stream or river system.

Small streams are called brooks or creeks.

Water sheds (Drainage Basin): Land where all water drains into a stream

DivideHigh land area that separates watersheds

Stream Load

All the materials that the stream carries

There are 3 ways that a stream carries a load:

1.Solution

2.Suspension

3.Bed Load

SolutionMaterial is carried in solution after it becomes

dissolved in a stream’s water.

Stream Load

Stream Load

Suspension

All particles small enough to be held up by the turbulence of a stream’s moving water are carried in suspension.

Silt, Clay, Sand

Stream Load

Bed Load

Large sediments that are too heavy to be held up by turbulent water.

Consists of sand, pebbles, and cobbles that the stream rolls and pushes along the bed of the stream.

Stream Load

Bed Load

As the particles move, they rub, scrape, and grind against one another or against solid rock of the streambed in a process called abrasion.

This causes the rocks to be polished and round.

Stream velocity and carrying capacity

The ability of a stream to transport material is called the carrying capacity.

Discharge = The measure of the volume of stream water that flows over a particular location within a given period of time.

Expressed in cubic meters per second (m3/s)

Stream Velocity & Carrying Capacity

Discharge = width x depth x velocity(m) (m) (m/s)

As discharge increases so does carrying capacity

Floodplains

Floods occur when water spills over the sides of a stream’s banks onto the adjacent land.

Floodplain: broad flat area of land that extends out from streams for excess flooding

Floods

Flood stage = level where a stream overflows its banks and the crest of the stream is at max height

Upstream flood = the flooding of a small area. They are localized and cause damage within a short period of time.

Downstream floods

Heavy accumulation of excess water from large regional drainage systems.

Causes extensive damage.

Flood monitoring and Warnings