Wetland and watershed exam 1

What is a watershed

An area directly tied to a water body and its deposits within a specific boundary of activity and drains to one outlet.

Rivers typically flow from an ________ Through a _______ to a _______

Upper, high-gradient erosion zone

Transitionzone

Low-gradient deposition zone

Headwater watersheds

- uppermost watersheds that transform rainfall and snowmelt runoff into streamflow

• 70-80% of total watershed areas

• Contribute most of the water reaching downstream river basins

1st order stream

unbranching stream channel. Doesn't have to be connected to a second-order stream; it can be connected to any order, just has to be unbranching.

2nd order

Two or more 1st order streams come together

3rd order

two or more 2nd order streams

What does it take to bump an order up to a higher order?

Two of the same order coming together.

Integrated watershed management:

The process of organizing and guiding land, water, and other natural resource use in a watershed to provide desired goods and services to people without negatively affecting soil and water resources

Negative Impacts on Watershed Hydrology

- Stream channelization

-Wetland drainage

-Woody debris removal

-Urbanization (% impervious)

Steps being made for Erosion Control (4)

Minimize agricultural erosion

Revegetate construction sites

Reclaim disturbed lands

Install grass filter strips

Preventative strategies

Preserve existing sustainable land use practices to prevent problems

"Land acquisition"

Restorative measures

restore conditions to a desirable level to allevuate identified problems

Steps being made to Retain Stormwater & Protect Floodplains

Control livestock access

Maintain riparian buffers

Preserve large woody debris

Remove migration barriers

only_____percent of the planet's water is available to its 8 billion people

0.007

The relationship between moisture content in the atmosphere, temperature, and vapor pressure determines...

the timing and amount of evaporation and precipitation

VP (vapor pressure)

the pressure exerted by a vapor that is in thermodynamic equilibrium with its condensed phases (solid or liquid) in a closed system at a given temperature

Unsaturated air masses can become saturated by either_______ or________

Cooling

the addition of moisture to the air mass

Precipitation occurs most commonly when an air mass is......

air mass is lifted, cooled, and reaches Saturated vapor pressure.

What happens when warm air is cooled?

Cold air cannot hold moisture, so when warm air is cooled, it drops water.

How are clouds developed?

The lifting of warm, moist air over a cold air front. Can be developed in a cold front (advancing cold) or warm front (receding cold front)

rain shadow effect

Moist air rises on one side, resulting in condensing water vapor to fall on one side, while dry descending air falls on the other, making it a dry desert.

Return period

how long it will be between rainfall events of a given magnitude

funneling effect

Water traveling down a canopy

Through fall

rain that falls through the leaves and branches of plants

80% of water reaches the forest floor in throughfall.

Stemflow

Water running down a plant stem or tree trunk

1-4% of water reaches the forest floor in stemflow.

Canopy interception is calculated by:

Subtracting gross precipitation by

throughfall and stemflow

Dense and multi-storied canopies (esp. in tropics) have ____ interception rates.

High

Evaporation

Net flow of water away from a surface (liquidwater to water vapor)

A steady state exists if the

amount of vapor arriving = the amount leaving

amount of vapor arriving = the amount leaving happens when

vapor pressure of water molecules at the evaporating surface is greater than the vapor pressure of the atmosphere.

Evapotranspiration - Simplified

• Direct evaporation from open water and soils

• Interception + evaporation losses

• Transpiration by plants

• Sublimation from snow

What is evapotranspiration influenced by

Influenced by land-use activities that alter water bodies and vegetation across the landscape

Transpiration

Evaporation from leaves and needles of plants (plant interiors) via stomata

Transpiration accounts for about _____ of the moisture in the atmosphere.

10%

How much water that is taken up by plants is transpired

(~90%)

What is transpiration affected by

temperature, relative humidity, wind and air movement, soil moisture availability, and plant type

Evapotranspiration - Controlling Factors (6)

- Water availability

-Energy availability

-Wind

-Humidity

-Vegetation

-Soil

Potential evapotranspiration

Measure of the ability of the atmosphere to remove water from the surface through processes of evaporation and transpiration, assuming no control on water supply.

Actual evapotranspiration

The quantity of water that is actually removed from a surface due to the process of evapotranspiration.

Water table

Where the water has reached a saturated state

Capillary fringe

region above the water table with water drawn up by capillary action

Infiltration

Process by which water enters and moves through the soil surface

What is infiltration controlled by

1) Precipitation Intensity (rate)

2) Soil factors

Infiltration capacity

maximum rate at which water can enter the soil surface

Infiltration rate

actual rate at which water enters soil surface

Percolation

deep, downward water movement in the soil

Organic litter and vegetation influence infiltration how?

• Hold water like a sponge and slow the rate of absorption

• Create a physical barrier to the A horizon and prevent surface sealing.

• Supply humus, which enhances soil structure and creates pores.

• Supports animal life, which creates macropores and channels.

Low infiltration rate to high infiltration rate soils

-Sodic clayey soils

- Clayey soils

-loam

-sandy and silty soils

-Sand

Soil porosity:

Soil pore size:

Amount of pore space in the soil.

varies based on particle size

Antecedent moisture content

relative moisture of soil at a point in time

Water always flows from...

higher water potential (i.e., wet soil) to lower water potential (i.e., drier soil)

Gravitational water

Free water moving through soil by the force of gravity

- Largely found in the macropores of soil

-Very little gravitational water is available to plants as it drains rapidly down the water table

Capillary water

- Water is held in the micropores of soil

- Water that composes the soil solution

- Is held in the soil because the surface tension properties (cohesion and adhesion) of the soil micropores and stronger than the force of gravity

-The main water available to plants

Hygroscopic water

- Forms as a very thin film surrounding soil particles

-Is bound tightly to the soil by adhesion

-Is generally not available to the plant

Saturation

All pores are filled with water

Field capacity

water in large pores are drained

Permanent wilting point

Plants can no longer extract water

Fine grained soils retain more water due

to greater surface area per volume

How tightly do fine grained soils hold onto water

hold it tightly so less is available for plant uptake.

Course soils can regain

less water, allowing more to percolate to ground water

Saturated hydraulic conductivity

(Ksat): The rate of water movement through completely saturated soil.

Unsaturated hydraulic conductivity

The rate of water movement through soil when it's not completely saturated--generally lower than Ksat due to trapped air.

Hydraulic Conductivity Influences

Pore size and connectivity

Soil texture

Soil structure

Compaction

Water content

Larger and more connected pores allow

water to move more freely.

Clay soils typically have lower conductivity than sandy soils due to

to their smaller pore spaces

Macroporosity increases

conductivity

Compaction Reduces pore space, leading to

lower hydraulic conductivity

Trapped air in unsaturated soil ______ the volume of pathways for water to flow.

reduces

Saturated soils reduced

infiltration rate

High clay content =___ conductivity

low

Chemical, pyhsical, and biological reason for management to understand streamflow dynamics

Chemical: Track pollutants

Physical: Flooding

Biological: Protect aquatic organisms habitats

Channel interception

precipitation that falls directly on water surface and becomes runoff

Surface runoff/overland stormflow

from precipitation or snowmelt that does not infiltrate the soil → major source of stormflow in agricultural, suburban, and urban watersheds

Subsurface stormflow

from precipitation or snowmelt that infiltrates the soil and flows rapidly through the soil into the stream channel → major source of stormflow in forested watersheds

Runoff is______ proportional to infiltration and _____ as soil becomes saturated

inversely

increases

Rate-limited stormflow

Infiltration excess overland flow.

Rate of supply exceeds the soils ability to infiltrate

Rate and volume limited storm flow

The soil is too saturated to take in any more water. Infiltration is at a net 0

Baseflow

Flow that occurs during periods between storms or during subfreezing weather; sustains streamflow during these periods

Ground water flow and Drainage from unsaturated zones are included in this definition

Groundwater flow

water moves into stream channels from saturated aquifer defined by permanentor perched water table

Drainage from unsaturated zones can...

can maintain streamflow for long periods of time in absence of a water table

The seasonal and annual flow patterns of a stream:

Pathways by which water enters a stream:

Perennial

Intermittent

Ephemeral

Perennial stream flow

stream flows year round with the potential exception of severe drought conditions

Intermittent stream flow

stream flows in the wet season only and ceases during other portions of the normal year

Ephemeral stream flow

stream flows in direct response to storm events (i.e., rainfall or snowmelt)

Saturated zones close to stream contribute...

flow directly to channel and respond most quickly to rain

Entire watershed generates stormflow only after _______________________

long storms and during wet seasons

source areas _________ most important zones in terms of streamflow generation

near stream

What do Stream Hydrographs do?

Shows change in stream discharge (Q) overtime in response to precipitation or snowmelt

What do A, B, C, and D represent in a stream hydrograph?

A = Channel interception

B = Surface runoff (i.e., overland flow)

C = Subsurface stormflow (i.e., interflow)

D = Baseflow - increases as infiltrated rainfall reaches the water table

Why does surface runoff rise and fall quickly on a hyrdograph?

It happens very quickly so it drops quickly as well, could take longer with clayey surfaces but won't go up without rain actively contributing to it. It will go lower or be stagnant without rain.

Fell faster than what the land could absorb

As land use becomes more urbanized, what happens to a hydrograph:

Total surface runoff increases while baseflow decreases

• Peak discharge increases

• Time to peak discharge decreases

• Watershed hydrology becomes more flashy and less stable

Water Quality

The chemical, physical, and biological characteristics of waterbased on standards established for of its intended use.

Water Pollution

Any physical, biological, or chemical change in water quality that adversely affects living organisms or makes water unsuitable for desired uses

Nonpoint source pollution

Scattered or diffuse, having no specific location of discharge.

• Agricultural fields

• Golf courses

• Residential lawns

• Parking lots

• Roadways

• Atmospheric deposition

Point Sources

Discharge of pollution from a specific location.

• Factories

• Power plants

• Drain pipes

Clean Water Act, what is it and what did it achieve?

Intended to restore and maintain the chemical, physical, and biological integrity of the nation's waters.

Effectively controlled point sources using National Pollutant Discharge Elimination System(NPDES) permits.

Clean Water Act (1972) Goal:

to return all U.S. surface waters to "fishable and swimmable" conditions

• Set goal for zero discharge of 126 priority toxic pollutants.

National Pollution Discharge Elimination System (NPDES)

o Requires permit and tracking of pollution discharges to surface waters.

o Delegates authority to states to manage.

o Resulted in dramatic improvement to US surface water quality.

Current legal framework for managing point source pollution

What did NEPA force industries and municipaties to do?

treat wastewater

Post-Clean Water Act: Progress

• Point-source pollution has declined dramatically

• Nearly all residents of urban areas now served by a waste water system that meets pollution discharge standards