• Smith and Punn Chapters 16 and 17
• Earth Revealed: movies. (http://www.learner.org/resources/series78.html)  Requires Windows media Player.  Sign in and view films 19,20, and 21.

Internet Sites to Explore:

• Hydrology
• The Water Cycle By Steve Graham, Claire Par, NASA's Earth Observatory
• BBC the Water Debate
• Glossary
• USGS Aquifer Basics http://capp.water.usgs.gov/aquiferBasics/carbrock.html

Terms: Hydrosphere, hydrology, water cycle, interior and exterior drainage system, drainage basin, stream, aquifer, aquitard, zones of aeration and saturation, base level, alluvial fan, delta, evapotranspiration, load, perennial stream, gaining and losing streams, hydrograph, BOD, point source and diffuse source of pollution

Hydrologic system

• Hydrosphere: The region of the solid earth that contains water
  • Components of the hydrosphere
    • Oceans (97.5%)
    • Ice (2%)
    • Organisms (Biosphere)
    • Terrestrial water (.0221%)
      • Ground water (.005%)
      • Lakes and Rivers (.0171%)
    • Earth's Water (USGS)
• water is constantly moving between the atmosphere and the hydrosphere--Hydrologic cycle (fig. 2)
• The hydrologic system can be adversely affected by human activity Importance of water: water use (USGS)

Terrestrial Water systems

The .0221% that makes up water on land is the water available for use. The two major reservoirs through which terrestrial water circulates are on the surface (surface water) and in the ground (ground water). During a storm runoff flowing over land percolates into the ground water system. This ground water either re-emerges in streams and lakes or is discharged directly into the ocean. It's the surface water that is largely responsible for the erosion of mountains and deposition sediment in terrestrial basins and the ocean. Over 90% of all sediment entering the ocean is carried by streams. Most terrestrial water systems have an exterior drainage, which means they terminate in the ocean. However, some systems, known as interior systems, terminate in a saline lake, playa, or sea with no outlet.
Surface water

Surface water includes all water in streams, lakes, and overland flow(runoff). Surface water systems typically include a drainage basin (tributary network), a main stream (transportation system), and delta (distributary system) or in the case of an arid interior system an alluvial fan. A Drainage basin, or watershed, is the entire area drained by a stream and its tributaries. A large drainage basin, such as the Mississippi basin, is composed of a hierarchy of smaller basins, such as the Ohio and Missouri river basins.A delta forms where the main stream reaches base level (e.g. the ocean). At this point deposition causes the main trunk to bifurcate into a number of distributary branches that composed the delta.

Base level is the elevation below which a stream cannot erode. The ultimate base level, such as that for the Mississippi River is the ocean. At this point both the stream gradient and flow velocity required to carry sediment become zero. Any sediment carried to a base level is deposited. A local base level, such as a lake or another stream, controls the depth of erosion of the stream flowing into it. For example, the base level of the Missouri River is the Mississippi River.

Figure 1. Mississippi Drainage Basin drains the interior of North America and contains a number of smaller drainages, such as the Missouri and Ohio rivers. The Mississippi delta is deposited in the Gulf of Mexico, the base level for the Mississippi River.(Modified from figure 16.4, Earth Revealed)

A hydrologic divide is boundaries across which water cannot flow. There are three types of divides, topographic, recharge and discharge divides.

• Topographic divides are topographically high areas between watershed. The perimeter of a drainage systems is defined by topographic divides.

Note: The continental divide of the U.S. the hydrologic divide between the Pacific and Atlantic drainage systems.

• Streams may act as either discharge or recharge divides depending on influent or effluent conditions. (See figure below)

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Ground water

ground water zones

• zone of aeration: The zone just below the surface where pores are filled with air but periodically saturated during storms. Water moves vertically down through the zone of aeration.
• zone of saturation: The zone of soil moisture where all pores are saturated.

	Water in the zone of aeration (vadose water) percolates vertically down until it reaches the water table. Water in the zone of saturation (phreatic water) follows the hydraulic gradient, flowing from areas of recharge to areas of discharge. Ground water will eventually resurface where it will flow into streams, the ocean, or seep from springs.
The ground water contribution to a stream is called base flow, not to be confused with base level which is the elevation (sea level) below which a stream cannot erode.  The ground water table, the boundary between the zone of aeration and zone of saturation, fluctuates seasonally as rates of rechange and discharge vary. (Image modified from Earth Revealed, McGraw Hill)

• the weathering and erosion of surface materials; rocks and sediment (exogenic processes)
• the distribution of the biosphere

• Precipitation
• Runoff (surface water; Horton overland flow, streams, etc.)
• Infiltration (enters groundwater system)
• Evapotranspiration (evaporation and transpiration)

• The rate at which the ground can absorb the water, known as the infiltration capacity of the ground is controlled by the permability of the soil and/rock composing the ground.

  Permeability is the ability of a material to transmit water. The permeability of ground materials is controlled by the volume of void space, also known as porosity, the size of the pores, and their degree of interconnection.

  • Types of porosity:
    • fracture porosity (rocks) and granular porosity (sediment)
      • granular porosity controlled by grain shape, sorting, compaction, and infilling of pores (e.g. cement)
      • fracture porosity is controlled by size and number of fractures
      • some clastic rocks such as sandstone or coquina may exhibit both a granular and fracture porosity
      • some rocks may have porous textural elements (e.g. vesicles)
• rainfall intensity, duration and timing: intensity and duration determines whether or not the infiltration capacity of soil is exceeded
• vegetation: Interception and transpiration is governed by vegetation type, distribution, and stage of growth.
• The percentage area covered by slope, and slope steepness decreases ponding and infiltration.

Streams

The term stream refers to any channelized flow whether it is a gully, creek, or large river.

• Importance
  • Streams are the principal agent of erosion responsible for carving the landscape.
  • Streams carry sediment to the ocean (baselevel) where it is deposited.
    • Material is carried in streams as suspended load, bed load, and dissolved load.
  • Stream provide an important habitat for wildlife
  • Streams provide water for wildlife and man
  • Agriculture proliferates on the fertile soils of river flood plains.
  • Large rivers provide transportation and easy access to water thereby encouraging industrial development.
    
• Problems
  • Poor management and ignorance of streams can result in flooding and environmental damage (i.e. pollution, destruction of wetlands, etc.).
  • Where a large river system is shared by more than one country political animosity can insue around the use and managment of the waters.

Conditions of stream flow

Based on contribution to ground water

effluent stream A stream that receives recharge(baseflow) from the ground water table because the water table intersects the stream channel.influent (loosing) stream: A stream that looses water to the ground because the water table lies below the channel.

Based on constancy of flow throughout the year

perennial: Perennial stream flow all year around, typically because the are effuent all year around.

• stable: Fluctuates little throughout the year
• flashy: Characterized by very high peak flows and very low low flows

intermittent: seasonally variable. May be effluent in the fall-spring and influent or dry during the summer.ephemeral: Flow only when it rains. Flutuates between influent and dry conditions.

Figure 3. Flow conditions relative to the ground water table. (Modified from figure 17.13, Earth Revealed.)

loosing stream: Discharge decreases downstream due to changes in climatic conditions or usage. Examples: The Nile and Colorado Rivers.
gaining stream: Most perennial stream flowing in the same climatic area.

Stream Channel Types

• Braided streams: characterized by highly variable discharge, easily eroded banks, and abundant coarse sediment load
• Meandering streams: more stable. Characterized meanders with cut banks and point bars.
• relevant terms: competence, capacity, load (dissolved load, suspended load, and bed load), thalweg 

• Significance:
  • reflect underlying geology and topography:
  • control to some extent how a stream will react (e.g. flood) during a storm
• Examples:
  • dendritic: branching pattern formed on gently dipping or flat-lying homogeneous rocks.
  • trellis: formed on gently folded sedimentary rocks where the principal stream occupies a belt of weaker strata.
  • deranged: irregular drainage formed in regions where the previous drainage was disorganized by glaciation
  • radial: pattern of radial tributaries formed around a central highland such as a volcanic peak.
  • rectangular: angular pattern formed by streams following belts of jointed or faulted rock.

• Within a given climatic region Dd reflects the permeability and erodibility of the ground
• controls to some extent how a stream will respond to a storm

• Components of stream flow
  • runoff: overland flow of water to a stream
  • baseflow: ground water contribution to a stream
• Determination of stream discharge: Q=Av
  • measurement at a gauging station using stage height and a rating curve
•  Hydrograph: A plot of discharge against time
  • shows how rapidly a stream responds to a storm
  • A baseflow separation performed on a hydrograph can be used to determine relative proportion of runoff and baseflow.

  Ipswich River daily flows

  Figure 3. Daily flows of the Ipswich River This graph was created by plotting the mean daily flows of the Ipswich River for the period shown at the based of graph. (Data from USGS Water Resources) The baseflow, or amount of ground water contribution, to the river can be determined by drawing a line connecting points at the base of each peak. By doing so you can estimate the relative amount of runoff and ground water feeding a river. Note that ground water levels are typically greatest in the spring and decrease rapidly during the summer.

Factors that influence flooding

• Drainage Basin characteristics
  • Size: Small basins can be easily overwhelmed by a large storm and are more prone to flooding
  • Basin orientation and direction of stream flow relative to storm track
  • Relief
  • Drainage basin pattern
  • Drainage density
  • Geology (regolith and bedrock characteristics; porosity and permeability)
• Storm characteristics

• Amount of precipitation
• Size of storm relative to basin size
• Speed or Duration
• Storm Track
• Timing relative to previous precipitation events and season
• Vegetation
  • amount
  • type
  • stage of growth
• Man
  • increased impermeable surface: increased runoff and decreased infiltration
  • removal of or change in vegetation
  • filling in of wetlands: decreased natural storage within a drainage basin
  • sewering: Increases runoff and provides a faster and more direct route to the stream
  • building levees: increases flood crest downstream
  • Ground water withdrawal and induced infiltration 
  Useful sites
  • How urbanization affects the hydrologic system (USGS)
  • MA low flow inventory (MA EOEA)

  Figure 5. Unit hydrograph.

  Problem: Over the last 40 years the drainage basin of a stream has be subject to widespread development. The diagram on the left is a unit hydrograph illustrating the response of the stream to storms of the same magnitude before and after urbanization. Answer the following questions: 1. How does urbanization affect the volume and timing of peak runoff flows? 2. How is baseflow affected by urbanization? 3. Explain how urbanization of a drainage basin results in these changes in stream flow. 4. What are the adverse effects of such changes to aquatic life, industry and society?

Formation of and erosion by streams

• Large rivers are commonly located within ancient rift valleys and fault zones (e.g. Connecticut River, Amazon River, Hudson River, etc.)
• Smaller streams are typically formed by headward erosion
• Stream valleys and flood plains are carved by downcutting and lateral planation by meandering
• The eroded material carried by a stream is called its load
  • bedload
  • suspended load
  • dissolved load
  • Size and volume of stream load: competence (caliber=largest size) and capacity (volume)
    • competence: function of flow velocity and channel slope
    • capacity: function of flow velocity and volume
• Terms: Base level, flood plain, lateral planation, peneplain, cutbank, point bar

Groundwater

Classification of zones based on degree of saturation

• Zone of aeration
• Zone of saturation
• Water table: surface of the zone of saturation

Classification of rock bodies or sediment layers based on permeability

• Aquifer: Saturated permeable rock body or layer
• Aquitard: semipermeable
• Aquiclude: impermeable

Classification of aquifers based on the the presence of an overlying aquiclude that results in internal pressure

• unconfined (water table) aquifer
  • Regional aquifer
  • Perched aquifer: Local body of water perched above an impermeable layer that lies above the regional aquifer
• confined (artesian) aquifer
  • flowing artesian aquifer: High pressure aquifers. Water in wells flows up to the surface

Rate of ground water flow

• Ground water typically flows at a rate of a few centimeters to a few meters per day.
• Darcy's Law: Q=KIA
  • K = coefficient of permeability
  • I = h/l (hydraulic gradient=the difference in elevation divided by the length of the flow path)
• Velocity = aKI
  • a = porosity

• Springs: areas of natural ground water discharge
  • types of springs
    • fracture springs
    • contact springs
• Wells: dug or drilled by man to extract water
  • Types of wells
    • water table
    • artesian

  Introduction to Basic Ground-water flow by the earthDr

• Pathogenic bacteria, viruses, and parasites--from sewage
• Chemical
  • Nitrate (blue-baby syndrome)--from human and and animal waste
  • Heavy metals (mercury, lead, cadmium, etc.)--from factory discharge, acid mine drainage, landfill leachates
  • Pesticides
  • Solvents and synthetic chemicals (industrial waste)
  • Gasoline
  • Natural sources (exacerbated by acid rain)
• BOD (biochemical oxygen demand): --introduction of organic matter, such as sewage: decreases oxygen content of water
• Heat: Power plants and factories--decreases oxygen content of water
• Radioactive waste

• Point source: Local areas of waste discharge--e.g. pipes, sewers, etc.
• Diffuse source (non point source): broad source area: landfills, feedlots, agricultural spreading of pesticides and fertilizers, mine leachates. 
  
  

  Non-point sources of pollution (Modified from Ohio State Fact Sheet)

  sediment	Nutrients (Fertilizers, Grease, Organic Matter)	Acids and Salts	Heavy Metals (Lead, Mercury, Zinc)	Toxic Chemicals (Pesticides, Organic, Inorganic Compounds)	Pathogens (Bacteria, Viruses)
  -Construction Sites -Mining Operations -Croplands -Logging Operations -Streambank and Shore Erosion -Grazed Woodland -Stormwater Runoff	-Croplands -Nurseries -Orchards -Livestock Operations -Gardens, Lawns, -Forests -Petroleum -Storage Areas -Landfills -Stormwater Runoff	-Irrigated Lands -Mining Operations -Stormwater Runoff -Landfills -Salt-water Intrusion	-Mining Operations -Vehicle Emissions -Stormwater Runoff -Landfills -Croplands, -Nurseries, Orchards -Building Sites -Gardens, Lawns -Landfills	-Croplands, Nurseries, Orchards -Building Sites -Gardens, Lawns -Landfills -Stormwater Runoff	-Domestic Sewage -Livestock Waste -Landfills

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  Additional Online Resources  

• EPA Environmental indicators of water quality
• Urban Stormwater pollution
• Chlorinated hydrocarbons
• Stresses on ecosystem health: Chemical Pollution