Exam 2 Water Resources

Lecture 6: Surface Water (Combined)

Key Concepts

Watershed

The total land area that drains water to a common point. Also called a drainage basin, river basin, or catchment.

Overland Flow

Runoff water moving across land toward a stream or river.

Headwaters

The source or beginning of a river.

Tributary

A smaller stream that flows into a larger river.

Confluence

The point where two streams or rivers meet.

Thalweg

The deepest part of a stream channel.

Hyporheic Zone

Region beneath and beside a stream where groundwater and surface water mix.

River Discharge

Amount of water flowing past a point per unit time.

Formula: $Q = A \times V$

$Q$ = Discharge
$A$ = Cross-sectional area
$V$ = Velocity

Rainfall-Runoff Equation

$Q = K \times I \times A$

$K$ = runoff coefficient
$I$ = rainfall intensity
$A$ = watershed area

Flow Meter

Instrument used to measure stream velocity.

Staff Gage

Measures water height (stage) in a river.

Hydrograph

Graph showing river discharge or water level over time.

Reservoir Storage Equation

$\text{Storage} = Q_i + G_i - Q_o - S - E$

$Q_i$ = surface inflow
$G_i$ = groundwater inflow
$Q_o$ = surface outflow
$S$ = seepage
$E$ = evaporation

Laminar Flow

Water moves in smooth, parallel layers.

Turbulent Flow

Chaotic, mixed water movement.

Sediment Transport

Dissolved Load

Materials dissolved in water.

Suspended Load

Particles carried within the water.

Bed Load

Particles moving along the bottom by:

Rolling
Sliding
Saltation (bouncing)

Sediment Pollution

EPA identifies sediment as the most common pollutant in streams, rivers, lakes, and reservoirs.

Problems:

Clogs pipes
Damages fish gills
Increases water treatment costs
Encourages harmful algal blooms

Prevention:

Use silt fences
Protect streamside vegetation
Avoid mowing near streams
Sweep instead of hosing driveways

Meandering River

A river with winding curves.

Oxbow Lake

A lake formed when a river meander is cut off.

Braided Rivers

Form when:

Sediment load is high
Gradient is low

Influent (Losing) Stream

Water moves from stream into groundwater.

Effluent Stream

Groundwater feeds water into the stream.

Types of Lakes

Crater
Cirque
Pluvial
Kettle
Reservoir
Oxbow
Tectonic
Solution
Animal-made

Lake Ecological Zones

Littoral Zone

Near shore
Plants grow here

Limnetic Zone

Open water

Profundal Zone

Dark bottom layer

Benthic Zone

Sediment layer
Decomposition occurs

Lake Overturn

Mixing of lake water that:

Reoxygenates deep water
Brings nutrients to the surface

Seiche

Oscillation of lake water caused by wind or pressure changes.

Lecture 7: Floods and Drought

Floods

Causes of Flooding

Thunderstorms
Snowmelt
Glacier melt
Ice jams
Monsoons

Predicted River Floods

Flooding that develops over a longer time and can often be forecasted.

Flash Floods

Sudden flooding occurring in less than $6\,\text{hours}$ due to heavy rainfall.

Human Activities That Increase Flooding

Paved surfaces
Deforestation
Agriculture
Wetland removal
Improper waste disposal

These increase runoff volume.

Flood Recurrence

1-Year Flood

$100\%$ annual chance

10-Year Flood

$10\%$ annual chance

100-Year Flood

$1\%$ annual chance

Flood Risk Assessment

Flood Hazard
Exposure
Vulnerability
Performance

Drought

Drought vs Aridity

Drought

Temporary
Abnormally dry conditions

Aridity

Permanent climate condition

Types of Drought

Meteorological

Below-normal precipitation.

Hydrological

Below-normal surface and groundwater.

Agricultural

Not enough water for crops.

Socioeconomic

Not enough water for people and communities.

Drought Indices

Percent of Normal

Palmer Drought Index

Surface Water Supply Index (SWSI)

Drought Preparation

Xeriscaping

Using low-water plants.

Shade Balls

Used to:

Reduce evaporation
Reduce algae growth
Block harmful UV effects

Lecture 8: Groundwater

Must-Know Terms

Groundwater

Water found in pore spaces beneath Earth's surface.

Sources of Groundwater

Meteoric
Connate
Juvenile
Seawater intrusion

Groundwater Recharge

Movement of water into groundwater storage.

Vadose Zone

Unsaturated zone above water table.

Saturated Zone

All pore spaces contain water.

Water Table

Upper surface of groundwater.

Aquifer

Permeable geologic formation that stores and yields water.

Types of Aquifers

Unconfined
Confined
Perched

Aquiclude

Layer that cannot transmit water to wells or springs.

Potentiometric Surface

Level water rises to in a well due to pressure.

Artesian Well/Spring

Pressurized water flowing from a confined aquifer.

Porosity

Percentage of pore space in a material.

Permeability

Ability of material to allow fluid movement.

Hydraulic Conductivity (K)

Rate of fluid flow through porous material.

Darcy's Law

$Q = K \times i \times A$

$Q$ = discharge
$K$ = hydraulic conductivity
$i$ = hydraulic gradient
$A$ = area

Dye Tracing

Technique used to track groundwater flow.

Cone of Depression

Lowering of water table around a pumping well.

Drawdown

Difference between original and lowered water level after pumping.

Ogallala Aquifer

Largest aquifer in North America.

Lecture 9: Water Quality

Major Water Quality Parameters

Temperature

Affects other water-quality measurements.

Thermal Pollution

Human-caused changes in water temperature.

Dissolved Oxygen (DO)

Oxygen available for aquatic organisms.

Normal water: $6-8\,\text{mg/L}$ DO

Hypoxia

Low oxygen conditions in water.

Algal Bloom

Rapid algae growth that can reduce dissolved oxygen.

pH

Measure of acidity or alkalinity.

Pure water: $\text{pH} = 7$

Redox

Oxidation-reduction status of water or soil.

Turbidity

Cloudiness caused by suspended particles.

Secchi Disk

Tool used to measure turbidity.

Secchi Depth

Depth at which the disk disappears from view.

Hardness

Amount of dissolved calcium, magnesium, and iron.

Salinity

Amount of dissolved salts in water.

Total Dissolved Solids (TDS)

Measure related to salinity and conductivity.