Watershed and Wetlands Lecture Notes

Practice flashcards covering key concepts from a lecture on watersheds and wetlands.

Why is it important to study watersheds and wetlands?

To understand how they function, how they’re managed, and why they matter for water quality, flooding, and ecosystems.

Name two watershed-related challenges expected in the coming decades.

Climate change impacts, urbanization, wetland loss, nutrient loading, sedimentation, aquatic ecosystem stress, water shortages from high-demand uses (like data centers).

How is a watershed best defined?

Land area draining water, sediments, and nutrients to one outlet.

From a geomorphic view, how does a river system change downstream?

Headwaters show erosion, the main stem is transitional, and the mouth shows deposition.

Why are headwaters important to watershed flow?

They generate most streamflow by transforming rainfall and snowmelt into runoff.

Two 2nd-order streams form a ___ order stream.

3rd

What does “integrated watershed management” mean?

Using land, water, and resources in a way that meets human needs (food, water, energy, recreation) without degrading soil/water resources while protecting ecosystems.

Restoring drained wetlands is an example of what type of watershed management?

Restorative management.

List two main goals of watershed management.

Improve water quality, reduce erosion/flooding, protect wetlands/streams.

Give two examples of negative human hydrology impacts.

Wetland drainage, channelization, woody debris removal, urbanization.

Name two erosion control strategies.

Re-vegetate disturbed sites, install grass filter strips, minimize agricultural erosion, reclaim disturbed lands.

Give two watershed management tools.

Flood storage, erosion control, channel/floodplain restoration, riparian buffers, sewage treatment.

Name one practice to retain stormwater and protect floodplains.

Maintain riparian buffers, control livestock access, preserve woody debris, or remove migration barriers.

The process where plants release water vapor is called ____.

Transpiration

Write the hydrologic budget equation.

P = RO + I + Q + ET ± ΔS

What happens when air cools beyond Saturated Vapor Pressure?

It becomes supersaturated, condensation forms clouds, and precipitation occurs.

Which type of front brings tall storm clouds and heavy rain?

Cold front.

What forms on the leeward side of mountains after orographic lift?

A rain shadow, which leads to drier conditions.

Write the small-scale project water storage equation.

ΔS = P - ET ± Q ± RO ± GF

What is the difference between standard and recording rain gauges?

Standard gauges collect rain, while recording gauges measure rainfall over time (e.g., using a tipping bucket).

Define “return period”.

The average time between rainfall events of a given magnitude.

Why are rainfall distribution models used in storm planning?

To predict runoff using synthetic arrangements of rainfall intensities over time.

What is throughfall?

Rain that passes through plant canopies to the forest floor.

For canopy interception to be considered a “loss,” what process must occur?

Evaporation.

Write the evapotranspiration formula.

ET = P - Q - ΔS - ΔI

Evaporation occurs when vapor pressure of water at the surface is ___ than atmospheric vapor pressure.

Greater

Why is lake evaporation lower in the Midwest?

Due to cooler temperatures and higher relative humidity.

List two components of evapotranspiration (ET).

Direct evaporation, transpiration, interception loss, or sublimation.

What percentage of water taken up by plants is typically transpired?

About 90%.

Name one method used to measure transpiration.

Lysimeters, porometry, or the tent method.

How does the ratio of evapotranspiration to precipitation (ET/P) differ in dry versus humid climates?

In dry climates, ET/P is high (most water is lost to the atmosphere). In humid climates, ET/P is lower (more water is stored or becomes runoff).

Define potential evapotranspiration.

The atmosphere’s ability to remove water if the supply is unlimited.

What primarily limits actual evapotranspiration?

The availability of water.

How can evapotranspiration (ET) affect streamflow on a daily basis?

Plants transpire during the day, which can lower streamflow; there is less ET at night.

Name two practices to reduce evapotranspiration losses.

Mulch, drought-tolerant species, reduced tillage, windbreaks, or strategic irrigation timing.

Define infiltration.

The process by which water enters and moves through the soil surface.

Define infiltration capacity.

The maximum rate at which water can enter the soil.

What happens when rainfall exceeds the infiltration capacity of the soil?

The excess water becomes surface runoff, leading to potential flooding and erosion.

Define percolation.

The deep downward movement of water in the soil.

Name one factor that increases infiltration.

Vegetation/organic litter, good soil structure, or macropores created by animals/roots.

What is the difference between porosity and pore size in soil?

Porosity refers to the total amount of pore space, while pore size refers to the size of those individual pores.

How does organic matter improve infiltration in soil?

It holds water like a sponge, creates pores, and supports organisms that contribute to soil structure.

What is antecedent soil moisture?

The moisture content present in the soil before a precipitation event occurs.

Water moves from ____ soil to ____ soil.

Wet → dry.

Why is gravitational water generally not available to plants?

It drains too quickly through macropores, moving below the root zone.

Which type of soil water is most usable by plants?

Capillary water.

Why is hygroscopic water unavailable to plants?

It’s bound too tightly to soil particles, even at the wilting point.

Which type of soil typically holds the most water?

Fine-textured soils, such as silt loam or clay loam.

Define hydraulic conductivity.

A measure of how easily water moves through soil.

Define Ksat (Saturated Hydraulic Conductivity).

The rate of water movement through fully saturated soil.

Why is unsaturated hydraulic conductivity typically slower than saturated hydraulic conductivity (Ksat)?

Air pockets within the soil pores reduce the pathways available for water flow.

Name two factors influencing hydraulic conductivity.

Soil texture, pore size/connectivity, compaction, or water content.

List two sources of streamflow.

Overland flow, subsurface stormflow, channel interception, or groundwater (baseflow).

On a stormflow graph, why does runoff typically increase over time during a storm event?

As the soil becomes saturated, its infiltration capacity decreases, leading to more surface runoff.

Which type of soil typically has the highest runoff?

Clay.

How do impervious surfaces affect infiltration and runoff?

They decrease infiltration and increase runoff.

What maintains baseflow in streams?

Groundwater discharge.

Write the stream discharge equation.

Q = V × A

Define an ephemeral stream.

A stream that flows only after rainfall or snowmelt events.

What does the Variable Source Area (VSA) concept explain regarding runoff?

It explains that only some parts of a watershed produce runoff, and these active runoff zones expand and contract with changing wetness conditions.

Define a hydrograph.

A graph showing stream discharge over time.

What is “lag time” in the context of a hydrograph?

The time between the peak rainfall intensity and the peak streamflow.

Which land use typically produces the sharpest hydrograph peaks?

Urban/commercial areas.

Define water quality.

The physical, chemical, and biological properties of water as compared to an intended use.

What law created NPDES permits and wetland regulation?

The Clean Water Act (1972).

Why is it important to monitor water quality?

To track impairments, protect human health and ecosystems, and maintain beneficial water uses.

Give one example of a point source pollutant and one example of a nonpoint source pollutant.

A point source pollutant is like a factory pipe discharge; a nonpoint source pollutant is like farm runoff.

What is the difference between suspended sediment and bedload?

Suspended sediment refers to particles floating in the water column, while bedload refers to larger particles deposited on the stream bottom that move by rolling or sliding.

What is the function of EPA’s “MyWaterway” site?

It shows information on water body impairments and related management plans.

Describe the process of eutrophication.

Eutrophication is a process where excessive nutrient input leads to algal blooms, which then cause low dissolved oxygen (DO) levels and can result in fish kills.

Which trophic state describes a water body that is nutrient-poor and typically clear?

Oligotrophic.

Below what dissolved oxygen (DO) level is considered stressful for fish?

Below 5 mg/L.

Name two non-nutrient related water quality issues.

Thermal pollution, conductivity, PFAS (per- and polyfluoroalkyl substances), pesticides, or pathogens.

Why does phosphorus typically release from lake bottoms under certain conditions?

Microbes use up dissolved oxygen, which reduces nitrate and iron, leading to the release of phosphate (PO4).

What is the difference between erosion and sedimentation?

Erosion is the detachment and transport of soil or rock, while sedimentation is the process of deposition of eroded material.

Which type of erosion is human-caused and typically faster than natural erosion?

Accelerated erosion.

Write the Universal Soil Loss Equation (USLE) formula.

A = R × K × LS × C × P

Name the three main types of wind erosion.

Creeping, saltation, and suspension.

Name two strategies to reduce wind erosion.

Residue cover, windbreaks, strip cropping, reduced tillage, or maintaining soil moisture.

Put the following water erosion types in order of progression: sheet, gully, rill.

Sheet erosion, followed by rill erosion, and then gully erosion.

Where is sediment concentration typically highest on a hydrograph during a storm event?

On the rising limb.

Name one best management practice for construction sites to control erosion.

Stabilizing disturbed areas as soon as possible, applying mulch, or retaining sediment on-site.

Name two farming practices designed to reduce erosion.

Using cover crops, contour strip cropping, conservation/no-till farming, terraces, or riparian buffers.

What are the common causes of slope failure?

Slope failure occurs when shear stress exceeds shear strength, often due to excess water, increased weight, or removal of stabilizing vegetation.