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Watersheds & Wetlands

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stacie stonebraker

on 12 May 2014

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Transcript of Watersheds & Wetlands

II. Major Drainage Patterns
A. Pennsylvania’s Rivers & Streams
III. Pennsylvania’s Drainage Patterns
A. Western PA
1. Many of the drainage patterns in this part of the state are dendritic.

2. Reason: most of the rock under the soil is massive sedimentary rock
IV. Watersheds
A. watershed (drainage basin) – a region drained by, or one that contributes water to, a stream, lake, or other body of water
Watersheds & Wetlands
I. Stream Characteristics
A. Stream Origins
1. source (head, headwaters): the place where any stream or river begins

2. mouth: the place where a stream or river ends by flowing into another body of water
B. Types of Flow
As a stream flows from its source to its mouth, it can flow in one of two ways.
1. laminar flow: occurs when water moves in straight paths that are parallel to the stream’s channel or bed

a. water flowing this way mixes very little as it moves downstream
3. The pattern of flow, whether laminar or turbulent, is determined by the stream’s velocity.

a. Streams and rivers with a slow velocity have a laminar flow, however true laminar flow in natural streams is rarely seen.

b. Faster velocities result in turbulent flow.
2. turbulent flow: occurs when water moves in tiny circular paths as it flows downstream
C. Sediment Load
1. sediment load: the kind and amount of particles that the water can carry

2. Sediments can be carried in 3 different ways, depending on the size and weight of the particles.
a. dissolved load: sediment carried in solution
• some sediment enters the stream as the water flows over rocks and soil, which dissolves some of the materials making up the rocks and soil into the water

• most of the dissolved load comes from groundwater returning to the Earth’s surface
b. suspended load: particles that don’t dissolve and yet are small enough to be in constant movement in the water
• often composed of silt and clay
• most of the river’s load is carried as suspended load

c. bed load: sediment carried along the bottom of the channel

• these are larger particles such as sand, gravel, pebbles, and boulders
D. River Deposits
1. Not only do rivers erode the land, they can often relocate it. When a river’s velocity decreases, sediment is dropped or deposited.

2. river bars: deposits that occur when a river slows down as it travels around a bend in its channel

a. made of sand and gravel
b. found on the inside of a river bend

3. Meanders
a. a meander is a curve in a river or stream

b. forms due to changes in velocity causing deposition and erosion
b. Any bend changes the velocity of the water inside and outside the curve. The water on the inside of the bend (closest to rock) travels slower than the water on the outside of the bend.

The slower water leaves sediment behind. At the same time, the faster water erodes away at the soil at the outside of the bend. So the curve becomes more pronounced.

c. Eventually, the curve becomes very pronounced as the processes of sedimentation (deposition) and erosion continue to shape the land and the river.
d. Typically, the more pronounced and numerous meanders are in a stream, the older the stream is since the process of forming a meander takes many, many years
5. Rivers also deposit sediment when they overflow or flood their banks.

a. flood plain: the part of a river valley that is covered during a flood

b. flood plains are very fertile areas of land and are often used for farming

c. the flood plains of PA’s rivers are usually highly farmed areas
1. PA has more miles of streams and rivers per square mile than most states. Among the major rivers that run through PA are:

a. Ohio b. Allegheny
c. Monongahela d. Genesee
e. Susquehanna f. Juniata
g. Delaware h. Lackawaxen
i. Lackawanna
2. The drainage patterns of these rivers and tributaries (feeder streams) depend largely on topography.
3. Topography: physical characteristics of the land
4. All drainage patterns are controlled by the types of rocks over which the rivers and streams flow, as well as the presence or lack of folds and faults in the rocks.
B. Dendritic Drainage Patterns
1. Most rivers and streams form this type of pattern, which resemble mature trees.

The main river or stream is the trunk, and the tributaries appear as the many branches of the trunk.
2. Dendritic patterns form where bedrock (rock beneath the soil) is uniform and massive. e.g. the plains region

3. Dendritic patterns are mainly a function of the slope of the land over which the stream or river flows.
C. Radial Drainage Patterns
1. Radial drainage forms when streams flow from a high central area such as a plateau, volcanic mountain, or other type of uplifted feature.

2. The pattern resembles the spokes in a bicycle tire, leading outward from a central point.
D. Rectangular Drainage Patterns

1. These are formed when bodies of rock are broken by a series of faults and other fractures.

2. Instead of the expected rounded curves, the “bends” in rectangular drainage systems form right angles in the stream

E. Trellis Drainage Patterns
1. Trellis drainage is actually a type of rectangular drainage.

2. In this pattern, the tributary streams are nearly parallel to each other.

3. These patterns form when sections of softer, nonresistant rocks alternate with sections of harder, resistant rocks
B. South-Central PA
1. This part of PA has a few significant fault lines (fractures in the Earth’s crust).

2. These faults formed as the Appalachian Mountains formed hundreds of millions of years ago.

3. Result: rectangular drainage patterns
C. Southeastern PA
1. Most of this area has a trellis pattern.

2. These drainage patterns are a result of folding that occurred as the Appalachian Mts. were formed. Millions of years of erosion has left resistant layers of rock alternating with nonresistant layers.

3. Streams and rivers flow in the valleys of nonresistant rocks while resistant rocks from the ridges separating the river systems.
D. Potter County

1. Potter county, in north-central PA, contains a classic example of a radial drainage pattern.

2. An unnamed hill rises 2,520 feet at a boundary between 3 of PA’s major watersheds (drainage basin). One basin drains north to the St. Lawrence River, another southwest to the Gulf of Mexico, and the third into the Atlantic Ocean to the east.

Please examine the following 2 maps of PA showing major rivers (figure 1.6) and fault lines & river basins (figure 1.8) for further understanding.
1. Watersheds are surrounded by topographic highs called divides.
2. divide: any ridge between two streams along which precipitation runs off
a. can be several feet to several thousand feet high

b. ex. Continental Divide – runs through Canada, U.S., Mexico, and into Central America – creates the separation between the water the drains into the Pacific Ocean and the water that drains into the Atlantic Ocean

c. the watersheds separated by divides can vary in size

B. Pennsylvania’s Watersheds
1. All of the fresh water in PA eventually drains into the Atlantic Ocean, so in a way the state is a giant watershed of the Atlantic.

2. The PA State Water Plan denotes 104 watersheds for the state’s freshwater systems.

3. Each watershed is subdivided into basins and sub-basins

4. We will examine 5 major watersheds in PA:

a. Great Lakes Basin (includes Genesee and Erie Basins)
b. Ohio River Basin
c. Susquehanna/Chesapeake Basin
d. Potomac Basin
e. Delaware Basin

C. Great Lakes Basin
1. Only about 1% of the GLB lies in PA. This part is divided into 2 sub-basins: the Erie Basin and the Genesee Basin.

2. Major freshwater bodies in the Erie Basin include:
a. Conneaut, Elk, and Walnut Creeks (all drain into Lake Erie)

3. The rivers and streams of the Genesee Basin flow through New York and drain into another of the Great Lakes, Lake Ontario.
D. Ohio River Basin
1. The ORB is PA’s second largest watershed, covering 16,000 square miles. Over 13 million people get their drinking water from the ORB (incl. about 3.5 million Pennsylvanians).

2. The largest river in the basin is the Ohio, whose headwaters are in Pittsburgh, where the Allegheny River meets the Monongehela River.

3. The ORB also includes Tionesta Creek, Mahoning Creek, Stonycreek River, the Lower and Upper Youghiogheny Rivers, Beaver River, and the Upper Ohio River.

E. Susquehanna / Chesapeake Basin
1. largest watershed in PA (covers about 46% of the state)

2. The Susquehanna River is the largest river in the basin, with its headwaters in New York’s Otsego Lake. The mouth of the Susquehanna River is the Chesapeake Bay.

3. Major tributaries of the Susquehanna include: the Lackawanna, Conestoga, West Branch Susquehanna, and Juniata Rivers plus the Loyalsock and Tuscarora Creeks.

F. Potomac Basin
1. Interestingly, the Potomac River does not flow through PA, yet a small portion of the basin is located within the state.

2. PA tributaries to the Potomac River include the river’s largest, the Shenandoah River. Also included are : the Marsh, Wills, Tonoloway, Licking, Rock, Conococheague, and Antietam Creeks.

3. Most of the water bodies in this basin, including the aforementioned creeks, drain from north to south.

G. Delaware Basin

1. third largest watershed of the state

2. Major water bodies of this basin are the Delaware River and its tributaries (Lackawaxen River; Upper, Middle, and Lower Lehigh Rivers; Maiden and Brandywine Creeks).

3. The water from these rivers and creeks is transferred to the Hudson Basin which supplies New York City with its freshwater needs

V. Stream Biology
Obviously, streams and rivers are aquatic ecosystems in which life seems to thrive.

Many plants, including mosses, grasses, & ferns, are found along the edge of streams.

In addition, most stream communities include 3 dominant groups of organisms – algae & other protists, invertebrates, and vertebrates.
A. Algae
1. algae: plant-like protists that make their own food, making them producers or autotrophs

2. Algae form the base of most aquatic food chains (remember, all food chains must start with a producer).

B. Animal-like Protists

1. These protists are consumers (heterotrophs). They include ciliates and paramecia among others, and they eat bacteria, sediments that contain bacteria, and algae.

2. Amoebae (plural) engulf their food by flowing around and over it (think The Blob).

3. Saprophytes are protists that feed on decaying organic material.

4. Protists that feed on other protists are called raptors.

C. Invertebrates
1. This common group of organisms includes insects, mollusks, and worms, to name just a few.
3. Many mollusks and worms spend their entire lives in water.

a. feed on algae and plants (making them primary consumers)

b. some are omnivores and carnivores

i. omnivore – organism that eats both plants and animals

ii. carnivore – organism that eats other animals
D. Vertebrates
1. One dominant group of stream vertebrates is the amphibians, such as salamanders and frogs.

2. All amphibians depend on water at various stages in their life cycles, while most adult amphibians live on land.

3. Fish are another dominant group of vertebrates.

VI. Factors that Affect Freshwater Ecosystems
Many factors affect the presence or absence of organisms in a stream or river. Recall that factors can be categorized as either biotic or abiotic.

It’s the interactions between biotic and abiotic factors that determine the number and kinds of organisms in any environment, including freshwater ecosystems.
A. Stream Order
1. A stream forms over time as runoff flows along tiny channels called rills. These rills join larger streams and eventually flow into a major river.

a. The smallest streams in a river system are first-order streams.

b. First-order streams join to form second-order streams, which in turn meet to form third-order streams, and so on.

c. In PA highlands, nearly 80% of the streams are either first- or second-order streams, with the remaining streams being either third- or fourth-order streams.

2. The size or order of a stream relates directly to the organisms that inhabit the ecosystem.
a. first-order streams – large insect populations and few if any fish

b. third- and fourth-order streams – plants and game fish dominate

c. larger streams in general – diverse populations of algae, fish, and many other aquatic organisms

B. Temperature
1. Causes of differences in a stream’s temperature
a. velocity of the water

b. depth – shallow is warmer (sunlight)

c. areas of low and high water circulation (temperature differs vertically)

d. vegetation (the more vegetation, the lower the temp.)

2. Seasonal changes in temperature
a. melting snow feeding into stream – lower temps

b. natural springs lower temp.

c. a thick tree canopy over a stream can lower temp as well (blocks sunlight)

3. Changes in temp affect the kinds and numbers of species in a stream

a. some organisms can tolerate a range of temps (e.g. carp, catfish)

b. other species can only survive in certain water temps (e.g. some algae, protists, trout)
C. Current and Velocity
1. Water currents in streams and rivers are unidirectional (they flow in one direction). This is very different from ocean currents.

a. As the water flows, it carries its load and other substances downstream. These substances, like nutrients, flow very quickly over organisms.

b. If the organisms don’t use these resources immediately, they have to wait for the current to bring more.

c. This set of circumstances influences the adaptations that stream organisms must have to survive.
2. The flow of water also exerts a definite force on stream organisms.
a. Species must adapt to this problem.

b. Some species, like mollusks, resist the force by attaching themselves onto objects.

c. Other species, like streamlined fish, just move with and against the current.

3. Velocity
a. The velocity of a stream changes with its course and its depth.

b. While a decrease in slope reduces velocity, the widening of a river and the smoothing of its bed downstream actually cause an increase in average stream velocity toward the river’s mouth.

c. Stream velocity is LOWER at the water’s surface and where the water meets the channel bed.
4. Substrate
a. substrate: the material that organisms live in, on, or around

b. Substrate of a stream is made of organic and inorganic particles.

i. Organic substrate includes algae and other small particles of matter that generally are used as food.

ii. Inorganic substrates are the pebbles and rocks in a stream and the silt, clay, and mud that make up the stream’s channel.

c. Most invertebrates live on or under rocky substrates (e.g. sponges). Some organisms live in the substrate (e.g. one type of dragonfly larva lives in the sandy river bed and uses a siphon to get oxygen from the water above it).

d. Some stream organisms use plants as substrates. Some flies deposit larvae on mosses, midges feed on algae that grow on leaves, in forests, beetles will use wood as a substrate.

D. Sunlight
1. The biodiversity of a stream or river is directly impacted by the amount of sunlight available to that stream.

2. Plants must have sunlight to thrive, and a lack of sunlight can adversely affect other organisms within the ecosystem. (Remember, plants are producers, which puts them at the base of all food chains. No plants, no consumers.)

3. Areas of a stream or river that receive little sunlight have far fewer organisms than those areas where sunlight is abundant and penetrates the water to great depths.
E. Turbidity
1. The amount of sunlight that penetrates a body of water depends on the water’s clarity.

2. turbidity: amount of suspended matter in water includes silt and clay, plankton, organic debris, and other nonliving materials

3. Factors affecting turbidity
a. increase in stream erosion
b. high water volume (heavy rains, melting snow)
c. temperature (warm water promotes growth of plankton)

F. Dissolved Solids
1. Common elements carried in the dissolved load of a river:
Magnesium, calcium, iron, sodium, potassium, sulfur, silicon, nitrogen, phosphorus

2. These elements are essential to organisms living in streams and rivers
a. calcium – bones, shells
b. silicon – shells of diatoms (protists) & sponges’ spicules
c. phophorus, magnesium, potassium – plant growth

3. Excess amounts of some elements can stimulate plant and algae growth beyond what is normal.
a. nitrogen and phosphorus

b. algal bloom – excessive growth of algae

c. too much algae – depletes dissolved oxygen in water and results in the death of many organisms

G. Dissolved Gases – dissolved gases are important to stream biodiversity; two in particular are oxygen and carbon dioxide with oxygen being the most important
H. Oxygen
1. oxygen in rivers and streams enters the water through the air

2. Water temperature, photosynthesis, and cellular respiration determine how much oxygen will enter the water.

3. As temperature increases, the amount of oxygen that will dissolve in water at atmospheric pressure decreases.

I. Carbon Dioxide
1. most in a stream or river comes from either the Earth’s atmosphere or its groundwater systems

2. another source are decomposition and respiration

3. photosynthesis removes carbon dioxide as well as organisms absorbing carbonate minerals from the water
J. Organic Matter
1. most organic matter is used as food; e.g. plankton, algae, bits of leaves and wood

2. too many nutrients – decrease in oxygen levels

3. too few nutrients – organisms will either travel to another part of the river looking for food or they will simply die for lack of nutrients

K. pH
1. pH: measure of its concentration of hydrogen ions ( H+) compared to concentration of hydroxide ions ( OH--)

2. pH ranges from 0 to 14, with 7 being neutral; a solution with a pH of less than 7 is acidic, over 7 is basic

3. Pure water has a pH of 7 – neutral. Rainwater and most streams are slightly acidic.

4. While slight changes in pH can be tolerated, acidification of freshwater bodies can greatly reduce organism populations.
5. Steams that are acidic due to acid rain or snow are usually acidic for only a short time. (results – fish kills, decrease in insects)

6. Acidic due to mine drainage – often lose their bottom dwelling organisms

Why? Mine drainage isn’t just acidic, it also has heavy metals and other pollutants, which settle to the bottom and get trapped in sediments. They enter organisms through diffusion or ingestion.
VII. Wetlands
A. wetland: an area that contains unique types of soil, is home to plants adapted to the wet environment, and contains water all year or at certain times of the year
e.g. bogs, swamps, marshes
2. swamp: forested wetland in which trees and bushes are the dominant plants

a. some swamp soils are rich in nutrients, others are not

b. soils drain very slowly

c. types of trees present can be used to classify swamps
i. conifer swamp: cedars, pines, spruces, hemlocks
ii. hardwood swamp: maples, willows, aspens, birches, elms, oaks
iii. may also see dogwoods and alders

d. animals: deer, raccoons, herons, egrets, woodpeckers, snakes, frogs and turtles
3. marsh: a wetland that generally forms at the mouth of a river or in areas where there is poor drainage

a. water that fills a marsh comes from nearby creeks, streams, and rivers

b. soils are rich in nutrients and support vegetation such as grasses, sedges, bulrushes, and cattails

c. animals: beavers, frogs, turtles, raccoons, muskrats, opossums, birds, and insects

B. Pennsylvania Wetlands

Legal definition of a wetland in PA according to Chapter 105 of the Commonwealth of Pennsylvania code:

Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.
1. Forested Wetlands

a. areas where the dominant plant types include mature woody trees

b. about 220,000 acres of PA’s wetlands are home to red and silver maples, black gums, river birches, and green ashes
C. Wetlands At Work
1. Habitat
a. Wetlands are home to hundreds of different species of bacteria, protists, plants, & animals including many organisms that are threatened (may soon become endangered) or endangered (may soon become extinct).

b. Wetlands only make up about 5% of the total land area of the lower 48 states of the US, yet they are home to nearly 35% of the threatened and endangered species in the US.



2. Food Factories

a. have very high primary productivity rates

b. plants are responsible for the majority of this activity

c. some organisms will eat the parts of plants that are above water, while the decomposing plant parts provide food and nutrients for bacteria, fungi, and protists along with some invertebrates

d. these organisms often provide food for many wetland vertebrates
3. Spawning Grounds and Nurseries

a. nearly 200 species of amphibians and all wild ducks, geese, swans, bitterns, and herons reproduce in wetlands

b. wetlands in the flood plains of larger rivers provide spawning habitats for many freshwater fish
4. Cycling Nutrients
a. Plants are the driving force and the defining factor for wetland ecosystems.

b. In using photosynthesis, plants use carbon dioxide and sun energy but release oxygen.

c. The oxygen is used for respiration in nearly all heterotrophs.

d. These elements, along with phophorus and nitrogen, are moved through the wetland in cycles driven by plants.

5. Buffer Zones
a. Wetlands are in many ways like natural sponges. They can absorb excess runoff and release it slowly back into the environment. This ability reduces flood damage to crops.

b. The roots of the wetland plants help to hold soil into place as well.

c. Along coastlines, wetlands can reduce the impact of waves and break-up stream and river currents. This provides a buffer for the storm surges brought on by hurricanes and tropical storms.
6. Pollution Control
a. Surprisingly, the number one water pollutant (by volume) in Pennsylvania is sediment.
b. By slowing water movement, wetlands play a role in reducing sediment pollution. This allows the sediment to settle and improves the water quality for wetland wildlife.
c. Air pollution is also prevented by wetlands. Many wetland plants store carbon rather than releasing it as carbon dioxide (a greenhouse gas that can affect global climates).

D. Suburban Swamps
1. PA’s waterways (creeks, streams, rivers) provided a means of transportation for goods and for consumption, and so were critical to the development of many cities in the state.
a. However, urbanization has disrupted and often times destroyed many of the wetlands that are associated with these bodies of water.

b. Today, much of the planning for urban growth uses a best-practices approach to wetlands.
2. The best-practices approach includes the preservation of open spaces in urban areas.

3. Loss of urban open space can have very negative effects on an area:

a. greatly reduces recreational areas
b. renders the area less attractive to businesses
c. may reduce the quality of air and water in the region
d. landscapes of the developed areas (concrete, nonvegetated land) may increase the risk of flooding

4. Preserving open space can have many benefits:

a. vegetation improves air and water quality
b. provide habitats for different kinds of animals
c. lessen the chances and effects of flooding
5. One kind of open space is the urban wetland. Some are remnants of streams and rivers that once flowed through areas prior to development. Others result from a poorly planned development (drainage ditches that collect rain runoff).

a. provide habitat for cattails, reeds, aquatic animals

b. buffer runoff from pavements, empty lots, etc.

VIII. Natural Events Affecting Watersheds and Wetlands
We’ve already discussed many human activities and events that can have drastic affects on watersheds and wetlands. Nature also plays a role in changing and influencing the watersheds, wetlands, and the organisms that inhabit them. Some of the changes are beneficial while others are detrimental.
A. Floods
1. very important to watersheds because they move nutrients and organic materials downstream

2. can be seasonal or from severe weather

3. can change the size and shape of a river channel

B. Erosion and Deposition

1. Channel shape is determined by the amount of sediment eroded; channel shape then affects factors such as velocity, discharge, and gradient, and stream biology

2. sediment transport is directly related to the amount and severity of precipitation received

C. Drought

1. drought: period in which the amount of precipitation that falls in an area is lower than normal

2. reduced water volume impacts clarity, salinity, temperature, pH, amount of sediment – severe changes in these can have adverse effects on organisms

3. extended droughts may lead to bodies of water disappearing completely, and the consequent lack of breeding and feeding grounds can greatly decrease the populations of many organisms

D. Volcanic Eruptions
1. Volcanic eruptions can trigger massive mudslides and the burning of forests

2. large volumes of ash and other debris can contaminate bodies of water and kill many organisms

G. Global Climate Change

1. a colder over-all climate of the Earth results in more fresh water being locked up in glaciers and ice caps, and the sea level drops

2. During a warmer over-all climate, the sea level rises which can cause flooding on coastal wetlands. The wetlands then shift toward land.
4. How a Meander Forms – One Scenario

a. an immovable obstacle, such as a large boulder, forces the stream to alter its path slightly, causing a slight bend


4. Many fish feed on algae. These fish are called grazers, strainers, or suckers, depending on their feeding strategies.

5. Other fish are predators (ex. pike, pickeral, gars).

6. detritivore: an organism that feeds by either shredding sediments that enter the stream or filtering their food directly from sediments in the water
Lesson 1.2
Lesson 1.3
Lesson 1.4
4. beneficial: enriches the flood plain by depositing large quantities of silt on the river’s banks

5. negative: can destroy wetland forests along the river bank, can relocate organisms far from their native habitats, can trigger landslides which cause massive sediment flow downhill
2. Nearly every stream ecosystem includes flies and beetles, which live in the water itself while in the larval stage.

a. shredders – flies that eat the tissue of other organisms, organic matter, and wood

b. Other flies act as predators, ingesting their prey whole or piercing the bodies and sucking the fluids out.

c. Many beetles catch and engulf prey or feed on decomposed organic matter.
6. Pollution Control
a. Surprisingly, the number one water pollutant (by volume) in Pennsylvania is sediment.

b. By slowing water movement, wetlands play a role in reducing sediment pollution. This allows the sediment to settle and improves the water quality for wetland wildlife.

c. Air pollution is also prevented by wetlands. Many wetland plants store carbon rather than releasing it as carbon dioxide (a greenhouse gas that can affect global climates).

F. Wind
1. powerful winds from severe weather can carry and drop large quantities of sediment into a body of water, which in turn reduces clarity and increases turbidity

2. wind influences the length of time a river or lake can keep its winter ice cap, which affects some physical and biological aspects of the body of water

4. Photosynthesis adds oxygen to the water. Organisms have many different ways of taking the oxygen out of the water in order to respire.

5. The current of a river or stream also affects the amount of oxygen.

a. decrease in speed – less oxygen available to organisms

b. some organisms have adaptations that control flow or create flow over their respiratory organs

6. decomposition of organic matter – uses up oxygen; happens faster in warm waters than in cold waters
7. There are 3 main reasons why many of PA’s streams and rivers are susceptible to acidification.

a. Much of PA receives some of the most acidic rainfall in the US.

b. The rocks in much of the state contain minerals that contribute to acidification.

c. PA has many coal mines.
1. bog: wetland in which soils consist predominantly of decomposed plant material (called peat or muck)

a. mosses are dominant plants in a bog

b. also includes shrubs, some evergreens, water lilies, pitcher plants, cranberries and blueberries

c. very acidic, contain little oxygen because of a lack of movement of water in and out of the wetland

d. animals include frogs, turtles, insects, certain birds (fish are limited due to the lack of oxygen)
How many wetlands do we have? Of nearly 29 million acres, about 407,000 acres are wetlands.

Over 4,000 of those acres have been restored as wetlands since 1990. Three general types of wetlands are recognized in PA: forested wetlands, scrub-shrub wetlands, and emergent wetlands
3. Emergent Wetlands
a. marshy areas where plants are rooted in soil but emerge above water

b. occupy about 52,000 acres of PA wetlands

c. common plants – rushes, grasses, sedges
2. Scrub-Shrub Wetlands

a. dominant plants are scrub and shrubs as well as trees that are less than 20 feet tall, such as alders and willows

b. occupy about 139,000 acres of PA’s wetlands
c. In PA, more than 500 plant species of concern live in or near wetlands.

d. It is also estimated that more than 80% of all of the state’s amphibians live in and around wetlands most of the time.

e. 25% of the state’s reptiles spend nearly all of their time in wetlands, and more than 120 species of birds in PA rely on wetlands for most of their life functions.
c. coastal wetlands are spawning areas for shellfish and commercial game fish (salmon, flounder, striped bass, bluefish...)

d. Obviously, these are vital areas for maintaining many different populations of organisms.

c. trap and filter out much of the iron, lead, copper, and other harmful substances present in most urban runoff

d. aid in treating large volumes of waste water: when storm runoff and treated sewage are channeled into urban wetlands, the water receive additional filtering before they are released back into streams and rivers
E. Fires
1. runoff can be increased from damaged or destroyed vegetation

2. erosion can be increased in a steep sloping watershed that has been affected by a forest fire
3. Salinity changes as salt water from the sea moves inward; this can result in salt-tolerant species replacing freshwater organisms.

4. The influx of water on the coastal wetlands can be so great that the wetlands become an open water environment; Louisiana is experiencing this pattern at a relatively rapid pace.
d. Stream velocity is at its FASTEST in the middle of the water column due to the least resistance.

e. Most species of fish are unaffected by velocity and can live nearly anywhere along a stream or river. Other organisms must stick to calmer waters (e.g. insects).
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