WATER ON AND UNDER GROUND

Objectives

• Define and describe the hydrologic cycle.• Identify the basic characteristics of streams.• Define drainage basin.• Describe how floods occur and what factors

may make them worse.• Define recurrence interval and show how it

is used to predict floods.• Define water table.• Identify two types of aquifers.

The Hydrologic Cycle

• Hydrology– The scientific study of water

• Evaporation– Water changes from a liquid into water

• Transpiration– Water taken up by plants passes into the

atmosphere

• Condensation– Water changes from a vapor into a liquid or a

solid

The Hydrologic Cycle

• Water in the Earth system– Deposition

• The process by which water changes from a vapor to a solid

– Precipitation• Water that has condensed in the atmosphere falls back to

the surface as rain, snow, or hail

– Surface runoff• Precipitation that drains over the land or stream channels

– Infiltration• The process by which water works its way into the ground

though small openings in the soil

The Hydrologic Cycle

The Hydrologic Cycle

The Hydrologic Cycle

How Water Affects Land• Streams and stream

flow– Stream

• A body of water that flows downslope along a clearly defined natural passageway

How Water Affects Land• Streams and

stream flow– Channel

• The clearly defined passageway through which a stream flows

– Straight– Meandering– Braided

How Water Affects Land• Streams and stream

flows– Gradient

• The steepness of a stream channel

– Discharge• The mount of water

passing by a point on a channel’s bank during a unit of time

– Load• The suspended and

dissolved sediment carried by a stream

How water Affects Land• Stream deposit

– Floodplain• The relatively flat valley floor adjacent to a stream

channel, • Inundated when the stream overflows its banks

How water Affects Land• Stream deposit

– Alluvium• Stream sediment• Unconsolidated

sediment • Recently deposited

(geologically speaking)

How water Affects Land• Stream deposit

– Delta

How water Affects Land

How Water Affects Land

• Drainage basin– The total area from which

water flows into a stream

• Divide– A topographic high that

separates adjacent drainage basins

• Lakes– Standing bodies of water

that have open surfaces, in direct contact with the atmosphere

Water as a Hazard and a Resource

• Floods– An event in which

a body of water overflows its banks

• Flood prediction and prevention– Flood frequency

curve– Recurrence interval– Channelization

Water as a Hazard and a Resource

• Hydrographs of stream discharge

Water as a Hazard and a Resource

Water as a Hazard and a Resource

Water as a Hazard and a Resource

• Flood Frequency Curve

Water as a Hazard and a Resource

• Surface water resources– Reliable water supply critical to human survival and health,

agriculture and other economic activities– Nearly 250 million people are designated as water-scarce

Case Study: Mono Lake

Freshwater Underground

• Ground water– Subsurface

water contained in pore spaces in regolith and bedrock

• Water table– The top surface

of the saturated zone

Freshwater Underground

• How groundwater moves– Porosity

• The percentage of the total volume of a body of rock or regolith that consists of open spaces (pores)

– Permeability• Measure of how easily a solid

allows fluids to pass through it

Freshwater Underground • How

groundwater moves (continued)– Percolation

• Groundwater seeps downward

• Flows under the influence of gravity

– Recharge• Replenishment of

groundwater

Freshwater Underground

• Where groundwater is stored– Aquifer

• A body of rock or regolith that is water saturated, porous, and permeable

– Aquiclude• A layer of

impermeable rock– Artesian well

Freshwater Underground• How groundwater

moves (continued)– Discharge

• Subsurface water leaves the saturated zone

• Becomes surface water

– Spring• Occurs where the

water table intersects the land surface

In Galveston, TX, pumping of groundwater causedSubsidence of property allowing sea water to flow In from Gulf of Mexico.

Freshwater Underground

• When groundwater dissolves rock– Karst topography– Sinkholes– Cave

• Underground open space

• A cavern is a system of connected caves

Lechuguilla Cave

Groundwater is the sole source of potable water for approx. 1.5+ million people in Suffolk County. Suffolk County is the most eastern county on Long Island and the location of our research.Population has increased due to urban sprawl from New York City since World War II, changing Suffolk County from predominantly agriculture land into urban land.  Notable sources of groundwater contamination was summarized by Nemickas et. al. and include:

Salt water intrusion caused by pumping Nitrates from fertilizers, septic systems, animal waste Industrial contaminants such as heavy metals, degreasers, detergents, dyes, solvents Landfills Petroleum products Pesticides Coliform Road salt

Critical Thinking

• List the many ways we depend on the availability of fresh water in our daily lives.

• Where does your community obtain its water supply (i.e., groundwater, surface source)? Is the quantity or the quality of the water threatened?

• What would happen to the sea level and the shoreline if great ice sheets built up on the land?