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

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

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 caused Subsidence 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 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?