Hydrology The study of water

Water Cycle

The Hydrosphere Where is all the worlds water? Oceans: 97% Ice caps and glaciers: 2% Surface water (lakes and streams): less than 1% Groundwater: less than 1% Atmosphere: very small part of hydrosphere (but very important)

What happens to water that precipitates to the ground? Infiltrate: groundwater Runoff: streams Evaporate: weather systems Trapped in depressions (puddles, lakes, etc)

What determines if water will infiltrate or runoff?

What determines if water will infiltrate or runoff? 1) Amount and Duration of Rainfall:  As the amount of rainfall increases, the likelihood that water will become surface runoff increases.  Also, as duration of rainfall increases (the length of time it is raining), the chance of the water becoming runoff increases. 

2) Porosity:  Larger pore spaces in soils allow more water to infiltrate the ground.  If there is no pore space on a surface, such as sidewalks, driveways, roads, and parking lots, there will be no infiltration and nearly all water will runoff! 3) Permeability: How well the pores are connected.

Check Point What percent of earths water is in oceans? 70% 55% 2% 97%

What determines if water will infiltrate or Runoff? 4) Slope of the Land:  Because of the force of gravity the slope of the land is a very important factor!  Steeper slopes promote more runoff as gravity pulls the water downhill. Areas with little or no slope will have more groundwater infiltration as gravity pulls the water down into the soil.

What determines if water will infiltrate or Runoff? 5) Vegetation:  Vegetation promotes infiltration and decreases runoff.  Plants slow the natural flow of water, and their roots absorb water while breaking up the soil, allowing more water to penetrate the earth.

Check Point When Water falls as precipitation it can do which of the following Runoff Evaporate Infiltrate All of the above

What determines if water will infiltrate or Runoff? 6) Condition of the Soil:  The condition of the soil refers to how wet or how dry the soil is.  Wet soil will allow less water to infiltrate the ground and promote surface runoff.  Dry soil normally allows for more water to infiltrate the ground and less to runoff. 

What determines if water will infiltrate or Runoff? 7) Seasonal Variations:  More rain occurs in certain seasons than in others.  Also, warmer weather can cause winter snows to melt, promoting both runoff and infiltration.

Runoff: the movement of water over land to points of lower elevations Learn more: Click here Problems with pollution Click here Fact: The mighty Mississippi River alone empties 612,000 cubic feet (ft3) of water into the Gulf of Mexico every second!!!!

Watershed An area of land which drains to a common river, lake, or body of water.  Therefore, watersheds are defined by the common body of water that surface runoff is flowing to. (Saginaw Bay Watershed)

Divide A high land area that separates on watershed from another. The water always flows away from the divide.

What is the arrow pointing to in the picture? Delta Tributary Divide Mouth

Saginaw Bay Watershed

Stream Load Materials in suspension- small particles like silt, clay and sand that are small enough to be held up by the turbulence of the stream. Bed Load- substance to large and heavy to be held up by the turbululent water. Made up of sand, pebbles, and cobbles that can be pushed and rolled across the streams bottom Materials in solution- dissolved minerals from rocks

Stream Carrying capacity Discharge-the measure of the volume of stream water that flows past a particular location within a given period of time. Discharge=width* depth*velocity

Flood Flood- occurs when water spills over the sides of a stream. Flood Plain- Flat area that is covered by access water during times of flooding Natural occurrence

Check point A stream that has a large cross-sectional area and is moving a t high rate of speed, would therefore have a high: Permeability Delta Discharge Floodplain

9.2 Streams Objectives Describe some physical features of streams Describe the relationship between meanders and stream flow Explain the process of rejuvenation in the stream development

Stream Development What do you need to make a stream Supply of water- the formation of a stream requires adequate water supply. Can be fed by rain or ground water. As a stream develops it changes the width and size and shapes of the land over which it flows.

Stream channels Headwaters: The region where water first accumulates to. Stream channel: The narrow pathway that the water carves over time Stream Banks: Hold the water from flowing outward

Formation of stream systems When was the last time you saw water run uphill? The driving force of a stream is gravity. Base Level- The elevation at which it enters another stream or body of water.

Base level

What happens as streams reach their base level? Far away from a base level the stream erodes large deep V’s because it has a lot of energy from the high elevation As a river gets closer to its base level it has less energy for downward erosion and erodes the sides of the streams making it wider.

Parts of a stream system Headwaters: stream flow begins Mouth: Stream enters lake or ocean Base level: Level at which stream no longer erodes (ocean=ultimate base level)

Learning Check Which River is closest to its base level A B

Work by Streams Erosion: Transporting away of surrounding earth Stream loads (eroded earth): dissolved load (Solution) suspended load (suspension) bed load Capacity: the amount of load a stream can hold

Cont. Deposition: settling of sediment when a stream slows Deltas: deposition of sediment at mouth of stream Point bars: inside of meander (curve) Natural levees: Deposition of sediment along river edge because of flooding

Cutbank Point bars Meanders Oxbows Ex. Pg. 235 in book Video

Learning check __________ is the elevation at which one stream enters another stream or body of water Base level Headwater Meander Erosion

Deposition of sediment Alluvial fans- stream looses its velocity due to a decrease of stream gradient. Sediment drops out and stream can dry out. Usually occurs at base of slopes.

Deposition of sediment Deltas- Loss of velocity Triangle shaped deposit where stream enters a large body of water video

Rejuvenation Rejuveation- “to make young again” A stream continues to down cut until it reaches its base level. If the base level drops due to geologic processes than the stream continues downcutting. This is how the Grand canyon formed video

Learning check What is about to occur within the next 100 years? Point bar Erosion Meander Oxbow lake

The end for today  Funny student