GEO 425 Hydrology Final

What is the source of most groundwater?

precipitation and infiltration

Infiltration

water moving from surface to subsurface

Percolation

water moving through the ground

Types of aquifers

- Confined vs. unconfined

- Polluted vs. non polluted

- High vs. low water availability

etc

What variables determine groundwater availability?

- climate

- compaction

- overuse

- etc idk

Water misconceptions

- Water always flows from high to low points

- water always flows from high to low pressure

- True: water always flows from high to low hydraulic head, elevation head, and pressure head

Confined aquifers

impermeable overlying layer with opening somewhere for recharge area

Unconfined aquifer

fully permeable, with full rechargeable area

Bernoulli: Steady and stationary flow

water is flowing at a consistent velocity (both magnitude and direction of flow stay the same)

- unsteady and transient flow: when magnitude and/or direction of flow change

Bernoulli's law

when one thing increases, the complementary thing decreases (?)

Vertical flow

water flows from deeper part to shallower part --> upward

porosity

percent of air within a soil column that is completely dry

permeability

the connectedness of pore spaces

Aquifuges

Rocks and soils that are neither porous nor permeable.

Aquitards

impermeable layers such as clay that hinder or prevent water movement

Artesian well

confined aquifer where water in well rises up higher in land surface; continuously pumping up because of weight and pressure

Perched groundwater and water table

small water table above an area that is not saturated (separated by underlying confining layer)

Potentiometric surface

imaginary surface that one obtains when connecting the hydraulic heads of an aquifer

Measuring hydraulic conductivity

Field techniques: borehole and pumping tests

Lab tests: core subsoils

estimate vs. absolute values

constant head permeameters

sample size and replication

Lakes

inland depressions containing standing water

- all over the world, but not evenly distributed (North America, high altitude locations)

How are lakes formed?

- Glacial erosion and deposition: Great Lakes formed from dead glacial ice in depressions; smaller kettle lakes; highest large lake in the world is Lake Titicaca in South America, formed by melted ice and snow filling a basin in the Andes Mountains

- Shifts in Earth's crust: tectonic lakes

- Craters of some extinct volcano: Caldera lakes

- Landslides: land slide blocks river and acts as dam (until lake erodes and blows it out)

- Oxbows: cut off river meanders

- Man-made: reservoirs (include many 'fingers' from dammed up, backed up tributaries)

Physical characteristics of lakes

- light: turbid lakes get darker at more shallow depths than clear lakes

- density: water gets less dense at warmer temperatures (or below 0C)

Lake stratification zones

- Ice (surface - if winter only)

- Epilimnion: top

- Thermocline: middle

- Hypolimnion: bottom

Lake overturn

- in temperate lakes, the changing of the seasons help move water in the lake (during Spring and Fall)

- tropical lakes often stay stratified because warm water always stays on the top

Lake zones

- Littoral zone: shallow water near shore

- limnetic zone: shallow water away from shore

- Photic zone: topmost layer of water

- Profundal zone: middle layer of water

- Benthic zone: deepest, bottom layer of water

Nutrient status: eutrophic systems

- lakes with high production

- associated with high nitrogen and phosphorus

- increase in growth of algae and other aquatic plants

- may experience oxygen depletion

- shallow murky water

Nutrient status: oligotrophic system

- water is clear and appears blue to blue green in the sunlight

- low production of organic matter, particularly phytoplankton

- oxygen concentration remains high

Nutrient status: dystrophic system

- nutrient poor peat bogs

- acidic, dark, humic waters

Human impact on lakes

- overfishing, pollution, and introduction of invasive species

- human activities can add heavy loads of silts and nutrients, especially N, P, and organic matter

Video: What happened to Tulare Lake?

disappeared when tributaries were redirected for agricultural purposes; came back after extreme floodings

Video: Precipitation events are expected to become:

more frequent and intense

Video: Subsidence and earth fissures

settling and fracturing of the ground because of groundwater and overuse

Video: Hot drought

drought driven by high temperatures

Video: wet years vs. dry years water sources

- Wet years: use surface water

- Dry years: use groundwater

Video: solutions to agricultural water overuse

- More efficient fertilizer applications

- repurposing non-productive areas

Video: Farming land use

Half of the world's land

Video: Colorado River Basin

- 15% of US crops come from here

- currently drying

Video: weather/water whiplash

severe droughts followed by severe precipitation events

Movie: Why were the dams built on the Elwha River

For hydroelectric power to develop logging and pulp mill industry

Movie: how did damming affect the Elwha River

- Salmon were blocked by the dam, so their populations dropped

- Reservoir increased predation and water temperatures

- Lack of sediment and woody debris transport

Movie: Who were the two primary parties

- Elwha tribe in favor of bringing down the dams because they relied on the river's ecosystem services

- Port Angeles and townspeople in favor of keeping up the dams because they relied on the employment and economic benefits provided by the dam

Movie: what were the ineffective solutions to salmon loss that maintained the dams

- Hatcheries to restore populations, but they were not well suited to the wild

- Legislation preventing natives from fishing

Movie: what was the legal reason for taking out the dams?

- dam licensure was up for renewal

- one of the dams was in the national park because it predated it, but you can't license a dam within the park

Movie: Elwha River Restoration Act

- passed by Congress in 1992 and signed by HW Bush for the government to buy and remove the dams

- action was delayed for decades

Movie: what was the primary conflict with taking out the dams?

Environmental impacts vs. economic impacts

Movie: when were the dams removed

2011-2013

Movie: how was restoration aided post-removal?

- planting native species along banks

- relocating adult fish to assist in reintegration

Movie: how long was the river dammed?

~100 years

Bart Study: Research question

whether and how forested land within an agriculturally dominated watershed alters stream nutrient concentrations

Bart study: major result

forest drainage basins have significantly lower nutrient concentrations compared to agricultural areas; forest cover is a stronger predictor of water quality than soil/geology

Bart Study: What does forest cover correlate with?

Better water quality; sites with forested drainage basins had lower concentrations of nutrients compared to more agricultural sites

Bart Study: What is measurable even in agriculturally dominated watersheds?

buffering effect of forest land; preserving forested areas can help mitigate nutrient pollution and protect stream water quality

Bart Study: is water-quality improvement absolute?

no, variability and localized hot spots exist; some forested area sites still showed elevated nutrient levels, so forest cover does not guarantee clean streams in all circumstances

Bart Study: What factor is most important in driving nutrient levels?

Land use (forest vs. agriculture); things like soil type and geology are not strong predictors of lower nutrient concentrations

Bart Study: Implications for watershed/environmental management

protecting and preserving forested lands (especially headwaters) within or upstream of agricultural watersheds is an effective strategy for reducing nutrient runoff and improving water quality in streams

Speaker: What does the Miami Conservatory District do?

- collects, analyzes, and manages water quantity and quality in the Great Miami watershed

- monitors changes in the water cycle and effects on the landscape

- Flood protection, water supply, and recreation

Speaker: What does the system consist of?

- 5 dry dams

- 55 miles of levees and floodwalls

- 185 floodgates

- 10,000 acres of natural floodplains

- 350,000 acres of land that stores water

Speaker: Change of water cycle

- over last 25 yrs, mean annual precipitation has mostly increased above the long term mean

- fewer dry days

- thunderstorms: intensity increase between april and june

- runoff: more runoff than the long term mean (same as precip

- surface component and baseflow: increasing

- evapotranspiration: not much change

Speaker: water cycle intensifying in region

- more flooding

- more storage at dams so levees don't overtop

- more streambank erosion

Speaker: adaptations for intensifying water cycle

- green infrastructure and stormwater management

- allowing streams the room to naturally meander and do what streams do

Field trip: Acton lake dam

- Earthen dam

- spills over concrete part automatically at high flow

- smoothness of spillway moves water quickly and prevents erosion

- residence time of months to years

- ^ droughts could have RT of decades, extreme storm events could have RT of days

Field trip: Rutger Preserve

- WPA built dam in 1930s

- built for water supply (municipality, agriculture)

- built for recreation (swimming hole)

- dam breached

- holds less volume of water than Acton lake and maintains flow

- low head dam

- removing dams because of safety, environmental impact (species isolation, sediment load, water temperature, methane emissions), water supply

Field trip: Peffer Park

- dam blown out, so stream is incising

- privately owned before for natural hockey rink, now Miami's

- planned to remove and create step pool

Beavers

nature's engineers; make channels more swampy and more like true natural state

Darcy's Law (Q)

Q=-KiA

Q = discharge (m^3/day)

K = hydraulic conductivity (m/day)

i = hydraulic gradient (unitless)

A = area (m^2)

Hydraulic gradient (i)

i = change in h/change in x = h2-h1/x2-x1

Volume flux density (q)

q = Q/A = -Ki

(m/day)

Hydraulic conductivity (K)

K = -q/i

q = volume density

i = hydraulic head

Infiltration depth

P/(ne-theta)

P = precipitation

ne = effective porosity

theta = volumetric water content

Infiltration velocity

Ve=f/(ne-theta)

f = Infiltration rate

ne = effective porosity

theta = volumetric water content

Effective velocity (Ve)

Ve = q/ne

q = volume flux density

ne = effective porosity

Effective porosity (ne)

ne = q/ve

q = volume flux density

ve = effective velocity