251 - Exam 4 - Water Resources

Dr Herrman | UWSP

Water Table

the line that represents the divide between the unsaturated zone and the saturated zone

When is the water table the highest?

during the spring because rainfall is more frequent

When is the water table the lowest?

during the summer because of lack of rainfall and evapotranspiration

Cone of depression

a localized dip or depression in the water table that forms around a well when water is pumped from it

Radius of influence

the area around a well where the water table is affected by the withdrawal of water

Drawdown

the change in the elevation in the water table elevation due to pumping efforts

Is fine sand or coarse gravel more conductive?

coarse gravel due to its larger pore spaces, resulting in a wider radius of influence

In the cone of depression, what is the distance between the pumping well and the furthest extent away from the well that you still observe a decline in the water table called?

radius of influence

Capillary Fringe

thin band directly above the water table where soil is partially saturated with groundwater due to adhesion and cohesion of water

'What influences capillary fringe?

soil texture

What soil texture moves water higher the easiest through capillary fringe?

clay due to smaller pore spaces

Aquiclude / Aquitard

the impermeable layer in the subsurface that has low permeability and restricts groundwater flow, usually separated by clay or bedrock

Confined Aquifer

an aquifer that is usually under immense pressure, with an aquiclude above it so it is trapped by bedrock or layers of thick clay

Artesian Well

A well drilled into a confined aquifer where groundwater rises to the surface under natural pressure, often creating a flowing well

Potentiometric Surface

the level the water rises in a well

Where is the potentiometric surface in a unconfined aquifer?

the water table

What is needed for an actively flowing Artesian well to occur on the landscape?

For the well to be in a confined aquifer and for the potentiometric surface to be above the well casing

How does groundwater flow?

high to low hydraulic head very slowly, usually to a common discharge / outlet point

Hydraulic Head

the elevation of the water table relative to sea level

recharge scenario

surface water is flowing into the groundwater

discharge scenrio

groundwater is discharging into the surface water

artificial recharge

specific areas, usually human made such as recharge basins and injection wells, are designated to recharge groundwater

What is true about the groundwater that is located deeper in the aquifer?

It fell on the ground further way from the location you are located at

Darcy’s Law

Q = s (or dh/dl) · K · A

In Darcy's Law (Q=s⋅K⋅A) what does s refer to?

Hydraulic gradient

Hydraulic gradient (s or dh/dl) (slope)

the difference in hydraulic head between two wells divided by the distance between those two wells

In Darcy's Law (Q=s⋅K⋅A) what does K refer to?

hydraulic conductivity

What is true about hydraulic conductivity (K)?

the smaller the particle size, the harder it is for water to move, so the lower the conductivity

What will result in a larger Hydraulic conductivity?

Material with large pore spaces

Slug Test

takes a known volume of water and pour it into the well, causing the water in the well to raise. measures the time it takes to get back into the original water table elevation because water poured forces its way into the aquifer

In Darcy's Law (Q=s⋅K⋅A) what does A refer to?

cross sectional area in cubic feet per day

Darcy’s Velocity

Specific discharge (q/A = dh/dl * K) and Seepage velocity (Vs = (dh/dl * K)/n)

What does N stand for in seepage velocity?

effective porosity (pore space)

How are water molecules bound?

through hydrogen bonds

T or F: water has a dipolar charge

True (dipole moments)

T or F: water is the only substance on the Earth’s surface that can be found in all 3 states

True: solid, liquid and gas

Gas

molecules moving very quickly with high energy

Liquid

a globby arrangement where density is high and temperature dependent

Water heat capacity

has one of the highest heat capacities of all substances on earth, requiring significant energy to freeze or boil

where is water the most dense?

4 degrees celsius

Solid

an orderly crystalline structure where density significantly decreases

When H₂O molecules are in a strict orderly structure which phase state is water in?

solid

Water as a universal solvent

can dissolve any polar substance (unequal electron sharing) easily due to its own dipolar nature

capillary action in regards to water movement

due to adhesion and cohesion, water can travel upwards of several hundred feet

Point-source pollutants

comes from a defined source point such as a pipe or a drain

non-point source pollutants

does not come from a defined point and is associated with landscape level pollution

Physical quality parameters

temperature and clarity

temperature

can change seasonally/ daily and with depth

temperature and dissolved oxygen

warm water has less dissolved oxygen, cold water has more dissolved oxygen

clarity

how well the light can penetrate the water influenced by phytoplankton and algae and measured by secchi depth, TSS and a turbidity meter

chemical quality parameters

nutrients, road salts, specific conductivity, heavy metals, organic pollutants, acidity

nutrients

when available in excessive amounts with no limitations, lead to excessive primary production and stimulate harmful algae blooms

Harmful algae blooms

stimulate decomposition and consume dissolved oxygen

Liebig Law of the Minimum

determines that the element needed in highest demand will limit overall production

Macronutrients

N, P and C

Micronutrients

K, Na, Ca, Mg, Fe, Mo, etc.

freshwater systems —> algae growth

phosphorous

saltwater system —> algae growth

nitrogen

what do terrestrial plants need?

N, P, K

Which nutrient tends to be the dominant limiting nutrient in saltwater ecosystems?

Nitrogen

what can cause a waterbody to have a dissolved oxygen percent saturation that is less than 100%?

Excessive respiration or decomposition

why is chloride becoming a concern in waterbodies?

due to road salt application on impervious surfaces and urban landscapes

what species is most at risk because of road salt application?

macroinvertebrates

What is the most common source of chloride contamination in surface waters of the northern latitude regions of the United States?

road salts

specific conductivity

measures how many ions are in a solution and the ability of water to pass a charge through a cm gap

What is true about specific conductivity?

the more ions, the more conductive

what does a high conductivity indicate (over 200 in freshwater)?

pollution

heavy metals

cause neurological disorders, cancer and other internal organ diseases. example such as arsenic can be found natural in parent material

organic pollutants

pesticides, herbicides, fungicides, insecticides, rodenticides cause mutations in various amphibian species

where do pesticides go after application?

uptake by plants, leached into groundwater, runoff into surface water

Hydrocarbons

aromatic, ring structure that is toxic to organisms and especially toxic when released into environment (Horizon Oil Spill)

PCBs (polychlorinated biphenyls)

used in electrical/industrial equipment, paints, plastics, and dyes in carbonless paper that is incredibly toxic to both humans and wildlife

PCBs have a half life of …?

23 years in rivers

T or F: PCBs are fat soluble

True (bioaccumulation)

Acidity

pH

the negative log of H+ that measures the concentration of H+

Acidity can….

increase the solubility of heavy metals and directly leads to mortality in aquatic organisms

Alkalinity

Measures the ability of a water body to consume proton or resist acidification

What is the source of alkalinity in parent material?

limestone

Sox and Nox (combustion)

releases nitrogen dioxide and sulfur dioxide gasses

Sox and Nox (in atmosphere)

creates sulfuric and nitric acid, which leads to acid rain

How was acid rain prevented/reduced?

scrubbers on power plants to reduce the amount of sulfur and nitrogen released. started sourcing “low sulfur” coal

biological quality parameters

dissolved oxygen, chlorophyll, pathogens, and fecal coliform units

how is DO measured if there is little to no biological activity present?

by temperature

what consumes dissolved oxygen?

respiration or decomposition, usually from algae / primary production

what is considered a dead zone or hypoxia?

less than 2mg/L

what is considered without oxygen or anoxia?

0mg/L

what stresses warmwater species?

less than 4mg/L

what stresses coldwater species?

less than 6mg/L

What pathogens are expected to be in the water and where do they come from?

bacteria, viruses, parasites that come from human and animal waste

fecal coliform units (FCUs)

a generic group of bacteria mainly found in feces of warm blooded animals

what do high levels of FCUs indicate?

presence of harmful pathogens

Chlorophyll A

a photosynthetic pigment in algae

Sestonic aglae

free floating, prevalent in lakes and deep rivers

Periphytic algae

attached to a substrate, prevalent in shallow rivers and low order streams

Rapid bioassessment quality parameter

IBI and EPT

IBI

electrofishing to collect data

what do high IBI scores indicate?

fish species are intolerant to pollution

EPT

sampling macroinvertebrates (Ephemeroptera, plecoptera, trichoptera)

what does it mean if you collect a high number of EPT?

it means that the river/stream has good water quality since EPT are pollution intolerant. So if you collect a high number of everything else but a low number of EPT, the water quality will likely be poor.

Eutrophication

Nutrient enrichment of water, causing algal blooms, oxygen depletion, and dead zones, primarily from human activities