Water Resources Exam 1 Notes

ENVR 3200

Pools . . .

store water (ex: the ocean, snowpack, atmospheric moisture, groundwater, etc.)

What do fluxes (flows) do?

They move water between pools (ex: groundwater discharge, evapotranspiration, etc.)

What US water sectors have the largest withdrawals?

Irrigation, then thermoelectric power, then public supply

Where does energy for the hydrological cycle come from?

The sun

_________ drives large-scale atmospheric circulation. How?

Solar heating; Uneven distribution of heating at Earth’s surface creates differences in air temperature that lead to thermal convection.

What is Hadley circulation? Include mentions of low and high pressure zones..

Low pressure zones are where moist air that’s been heated rises vertically upward, cooling as it rises. Air from higher pressure zones rushes in to fill the gaps (convection). As the warm air rises and cools, moisture is more likely to condense and form clouds when the air is cool, eventually leading to rainfall. Eventually, the rising air reaches the tropopause; this now-drier air is diverted either north or south. As the air flows away from the equator, it continues to cool and become more dense; at about 30 degrees S and N, the air sinks back to the surface and flows back to the equator along the surface; this is often referred to as a high-pressure zone.

What is the ITCZ?

Intertropical convergence zone; this is where surface air flows returning from 30 degrees S or N (latitude) converge on a zone near the equator. Regions in this zone typically receive a lot of rain.

How do the locations of the world’s major deserts relate to atmospheric cycling and where are they located?

They’re typically located near 30 degrees N or S. At these locations, cool, dry air is typically descending from the atmosphere. These areas are characterized by both drier air and less precipitation.

What are the three major atmospheric cells located, and what are the latitudal cutoffs?

Hadley, mid-latitude and polar cells. Hadley: 0→30 degrees; Mid-latitude: 30→60; polar: 60→90. This is reflected over the equator.

What is tropopause?

The atmospheric boundary layer separating the upper (stratosphere) and lower (troposphere) atmosphere

How are polar cells characterized?

By strong cooling near the poles and resulting downward flow

A westerly wind comes from ____, goes ____.

comes from the west, goes east.

How do the locations of the ITCZ and Hadley cells change over the course of the year?

They shift towards the hemisphere receiving the most solar radiation, and the shift in precipitation patterns throughout the year reflect this.

What is the Coriolis effect?

The Earth spins west to east. As you get further from the poles, the radius of rotation increases, and linear = angular x radius. Due to the rotation of the earth, if you have a wind originating at the North pole and is moving south, it won’t have enough velocity to keep up with the Earth’s rotation and will divert west (easterly wind)

A cyclone in the Northern Hemisphere rotates _______. Why?

Counterclockwise; air coming from N. pole has insufficient angular velocity to keep up with Earth’s rotation (diverts west, easterly wind), and air coming from equator has too much (diverts east, westerly wind), creates counterclockwise rotation for cyclone.

The Walker Circulation cell over the _____ is the primary ______ circulation feature. How does it work? What do disruptions look like, and what do they cause?

Pacific; longitudinal. In normal conditions, trade winds push warm water West and causes cool water to well up on the South American coast (fill the space left behind); air then cycles back (from above) west to east. In El Niño conditions, western circulation fails (both at surface and in atmosphere; both sides of the cell both push towards center) causing less S. American upwelling, (MAYBE, CHECK) more precipitation over the ocean. In La Niña conditions, extra strong convection drives even more warm water west, leading to extra South American upwelling.

What are trade winds?

Steady, predictable east-to-west prevailing winds that blow across the Earth’s tropical and subtropical regions, roughly between 30 degrees N and S latitude.

What are the four necessary conditions for precipitation?

Precipitable water (water in the atmosphere above the surface), continuing moisture supply/transport, condensation (conditions that change water from a vapor to liquid or solid phases, caused by changes to temperature or pressure) and hydrometeor growth processes (a series of complex processes take small condensed particles to larger ones that then fall as precipitation).

What are the three types of condensation? What gets an honorable mention?

Convergence, convective, and orthographic, with a special mention for cloud condensation nuclei.

Condensation is due mostly to . . .

Decreasing temperature/air rising. Convergence zones like the ITCZ and cold fronts create ideal conditions for condensation.

How does a cold front work, what is it?

A cold front is a boundary between a mass of relatively cold air that is pushing into a mass of relatively warm air. It forces warm air to rise over the wedge of cold air (less dense), creates condensation and often precipitation.

How do convective cycles vary by season?

In spring/summer, land is warmer than the ocean. Warm air will rise over the land, cool air sinks over the ocean. Moist air blows along the surface from ocean to land. Moisture condenses mainly above land as air rises. In winter, land is cooler than the ocean. Now air rises above the ocean, sinks above land, and we see more precipitation over the ocean.

What is orthographic precipitation?

Moving air over mountains forces it to rise, and if the air has moisture, clouds form and rain (orthographic precipitation) will occur on the windward side of the mountain. On the other side, air descends, clouds may evaporate, and this means many of the areas downwind of a mountain are arid or semi-arid.

What are cloud condensation nuclei?

Particles in the atmosphere (sea salt, sulfate, soil, dust, smoke) which promotes condensation of water vapor into clouds.

What makes precipitation and evapotranspiration difficult to measure? (4 items)

Spatial variability and resolution (measurements vary in different areas and are influenced by structures, tree coverage, etc). Temporal variability and resolution (variation over time). Measurements can alter the process (tools can impact the conditions) and measurements can have errors (wind and rain splash + alter water caught, snow needs to be accounted for, obstructions can alter water weight)

The simplest approach to measure precipitation is just to use a bucket or graduated cylinder. How does it work? What are the pros and cons?

You place a bucket, measure precipitation levels. Pros: simple with few failure conditions, cheap and can be put in a lot of places. Cons: no rate observations, only volume; labor intensive with lots of gages

A “tipping bucket” rain gauge is the “gold standard” but still has its own problems. How does it work and what are its pros and cons?

A funnel feeds into a bucket with a little metal piece that fills with water. When it fills to a certain level, it tips, and a record switch records this. Pros: reliable and accurate, generates a moderate amount of rate information, and newer ones can include telemetry. Cons: rate limits are based on max bucket tipping speed; NOT cheap.

There are two methods that give areal, not only local, information on precipitation. What are they, what do they do?

Radar → estimates precipitation based on reflections of microwave radiation; needs line-of-sight measure precipitation, so uses are limited in mountains. Satellites → estimate precipitation based on cloud height and “brightness” temperature; can estimate ocean precipitation

______ and ______ account for a great deal of mountain precipitation and later runoff; they act as natural “water towers”.

Snow and glaciers

What is snow depth (h, L)?

It’s the depth (or “height” of snow cover)

What is snow water equivalent (SWE, L)?

It’s the depth of water that would have the same mass as the column of snow.

What is snow density (ρs, M/L3 or [])? What is an equation for it?

It is the mass of water per unit volume of snow. ρ_s = SWE/h

What is snow cover?

It is the area (or fraction of an area) covered by snow.

Snow and glaciers have ____ daily and seasonal release patterns.

Unique

What are snow tubes used to measure, how do they work? What are some pros and cons?

Snow tubes → measuring gives you depth, weighing the filled tube gives you SWE. These provide good SWE estimates when and where they are done. However, they can be labor intensive and do not give information about the snowfall or melt rate.

What are snow pillows and what are they used for? What are some pros and cons?

Snow pillows measure SWE based on its weight; it consists of an antifreeze-filled pillow linked to a pressure transducer. It measures snow depth with an acoustic sensor. Cons: it’s expensive and requires a large footprint, meaning it generally has to be done in open fields/meadows.

What is a radiometer, what does it measure and how?

They estimate snow cover across the globe and snow emissions models/field measurements can be used to estimate SWE by looking at the “brightness temperature” of the ground.

What is LIDAR (Light Detection and Ranging), and what does it measure? Pros and cons?

Lasers; A flight is done with the ground bare to create a high quality DEM (digital elevation model) baseline. Snow depth is the elevation difference between baseline map and the map creed from a flight after it snowed. Pros: modelling takes very accurate snow depth to SWE readings based on a few point measurements. Cons: expensive and requires expert supervision.

What is evapotranspiration? What does it require? What is evaporation vs transpiration?

The net flux from the liquid or solid phase to the vapor phase in the atmosphere. It requires water, energy, and vapor transport away from the evaporative surface. Evaporation → net flux from soil, water, or ice surfaces. Transpiration → net flux through plants.

What is potential evapotranspiration?

The evapotranspiration that would occur from a wet surface under a specific set of meteorological conditions.

To measure evapotranspiration, you can use a bucket. How does this work, what are pros/cons?

Fill a bucket with water; pros: simple, few failure conditions. Cons: measures evaporation only, need to calibrate to vegetated surface. Pan sides can strongly affect evaporation (ex: if metal, it heats)→ needs to be calibrate the measurements to accurately reflect evaporation from an open body of water

FINSIH TOMORROW → file:///C:/Users/nanic/Downloads/lecture4_atmosphere.pdf

To measure evapotranspiration, you can also use a “weighing lysimeter”. How does it work, what are the pros and cons?

It tracks all the water that comes into or goes out of a “soil monolith” by weight or gauges. Pros: it’s a direct measure of evapotranspiration. Cons: requires that the soil monolith vegetation is representative of surrounding vegetation.

Porometry and sap flux are two methods of measuring ______. What are they, what are drawbacks?

Transpiration; porometry measures the humidity change in an enclosed chamber around a leaf. Sap flux approaches measure the speed of a sap flow using heat as a tracer. Drawbacks: it takes very local measurements, which need to be scaled up to the tree and then the field or plot. It assumes physical impacts of inserting/applying the equipment doesn’t alter transpiration, and it only can measure transpiration, not evaporation.

What water source (think general terms) is most used by humans?

Surface water

What (name of a place) water system holds 20% of the Earth’s fresh surface water? What are some unique characteristics about them?

The Great Lakes; they have characteristics typically associated with seas, such as waves, really sustained winds, substantial depths (elevation distance between Lake Superior/Huron/Eerie and the Saint Lawerence River is equal to the height of a skyscraper. All the Great Lakes except Erie have depths below sea level. They’re sometimes called inland seas and were carved by glaciers.

What are the three types of lakes in terms of sources/sinks? What are their inputs/outputs?

1.) Seepage lake → Inputs: groundwater and local runoff; outputs: groundwater and evaporation. 2.) Groundwater drainage lake → inputs: groundwater and local runoff; outputs: groundwater, evaporation, and outflow stream. 3.) Drainage lake → inputs: groundwater, local runoff, and inflow stream; outputs: groundwater, evaporation, and outflow stream.

What are the three types of lake in terms of position?

Seepage lakes are often isolated. Headwater drainage lakes are drainage lakes with less than 4 mi2 of watershed feeding into it, and are often positioned higher up in a river or catchment system. A lowland drainage lake is a drainage lake has over 4mi2 of watershed feeding into it, are often fed by large, major inflowing streams.

What are the three different categories for lake productivity? (Just the names)

Oligotropic, mesotrophic, eutrophic.

What are the characteristics of an oligotrophic lake?

Have low nutrient concentrations/planktonic growths and low plant growth. Typically occur in watersheds with thinner or organic-poor soils. Generally have a steep shoreline and bottom gradient, which are somewhere from sandy to rocky. These are coldwater fisheries and have high DO, though temperature stratification can develop. A small fraction of the watershed feeds into them.

What are the characteristics of a mesotrophic lake? (I don’t have many details)

They have intermediate nutrient concentrations and plant growths.

What are the characteristics of a eutrophic lake?

High nutrient concentrations and plant growth. High levels of biological productivity, abundant algae and plant beds, generally occur in watersheds with organic rich soils and have substantial sediment accumulation at the lake bottom. Lake bottom may have few plants because light is scattered by algae in the column above. Low DO at the bottom of the lake (depleted by decomposing organic matter) and this is a warm water fishery.

Can lakes change productivity levels? What factors impact this?

Over the course of (usually) a thousand years, a lake can evolve from oligotrophic → mesotrophic, and after hundreds, mesotrophic → eutrophic. Nutrient pollution (fertilizers, industrial discharge, etc) can shorten this time span to decades

_____ lakes can lead to anoxic water. Why?

Eutrophic; due to increased biochemical oxygen demand

What does mixing in a lake often look like? (In deep lakes, in shallow lakes, seasonal variations)

It’s common for there to be stratified zones; in a deep lake, there’s often a cold water layer with low/no DO. Thermocline (layer separating distinct temperature change) prevents mixing. On top, there’s a warmer layer that mixes and gets its oxygen contact refreshed with surface contact. Shallow lakes don’t have this severe thermal stratification and water cycles. Seasonal mixing: In winter, water typicalyl stratifies, unequal DO between layers. In fall (lake cools) and spring (lake warms), the lake mixes well (circulates) and DO is constant throughout. In summer, thermocline develops, stratifies again, creates temp divide, higher DO at top.

What are the characteristics of lake residence time? What about the drainage basin area and lake area?

How do oxbow lakes form?

They’re formed by a meandering river migrating across a floodplain. Imagine a river going from a slight wiggle path to an increasingly exaggerated S-shaped curve. Ends of the curve eventually touch, sediment gets built up at the turns, and cuts off a c-shaped segment of the river.

How do glaciers form lakes? How does this impact lake formation?

As glaciers move downslope, they scour the land and carve out depressions, which are then filled when the glacier melts as the climate warms. Because glaciers are found in the north, lakes are more prominent in the northern latitudes.

Lakes in closed basins often end up being ____.

Salty

What is the story of the Aral Sea?

Used to be a huge fishery, it was slightly saline because it was landlocked. Soviet Union withdrew unsustainable amounts for irrigation, now the lake is nearly gone and is over 3x more salty than salt water.

Why do people build dams/reservoirs? (5 reasons)

Water supply, hydroelectric power, recreation, flood control, transportation (a little bit).

What is the most common primary purpose of dams in the US? 2nd most common?

Recreation, then flood control.

What is a dam? (simple)

A structure to retain water

What is a reservoir? (simple)

A water body controlled by a dam.

What are outlet works?

Dam facilities for the controlled release of water. Typically towards the base, that house thing.

What are spillways?

Facilities for the controlled or uncontrolled release of water. At the top of the dam.

What is an embankment dam?

Constructed from compacted soil or rock with an impervious core. 80% of large dams in the US are this type. Transfers entire water load downward, looks like a bell curve.

What is a gravity dam?

Constructed with concrete/stone masonry, transfers entire water load downward, functions by having a lot of mass and being very hard to move. Typically span narrow widths in areas with bedrock foundations.

What is an arch dam?

Concrete, designed to transfer water load into adjacent rock formations, only constructed in canyons with strong walls. Thin walls, requires less material because canyon bears bulk of load. Arches inward

What is a buttress dam?

Reinforced concrete; transfers load to bottom and buttresses (buttresses are column supports)

What is live storage? (dams)

The usable storage capacity of a dam that can be filled during wet months and used during dry months.

What a flood pool? (dams)

Storage that is reserved for high flows to prevent flooding

What is dead storage? (dams)

Storage below the lowest outlet, can’t be used

Reservoir fills with _____ over time, _____ storage. What does the distribution look like?

Sediment; storage. Closest to the dam is fine sediment, coarser deposits are a bit further back. (they have higher settling velocity)

What are some upstream problems with reservoirs or dams?

CAn displace people and destroy cultural/historical sites. Disrupts migratory pathways. Reservoirs will fill with sediment over time. River recreation is exchanged for flatwater recreation. New mass of water can cause earthquakes.

What are some downstream problems with rivers or dams?

Alters flow, shifts in sediment flux can starve deltas and other systems of sediment. Changes in water temperature or dissolved gases have substantial ecological effects. Dam failure creates the possibility of very large floods.

What is a dam’s hazard potential?

A measure of how dangerous it would be if that dam failed.

What is a dam’s condition assessment?

A measure of the dam’s condition, how it’s holding up.

What makes a dam high risk?

High hazard potential and unsatisfactory/poor condition rating.

How old, on average, are dams in the United States?

57 years old (50-60 years)

In the US, how does the dam removal rate compare to the dam creation rate?

They’re about equal.

Is dam removal usually good or bad?

It’s complicated. Immediately after removal, there’s disturbance from the deconstruction, rapid reservoir erosion, downstream sedimentation, ecosystem disturbance. Afterwards, sometimes it goes well, and the ecosystem flourishes, sediment, flow and native species connectivity is restored. Sometimes it goes bad and there is widespread contaminant transport, invasive species dispersal.

What are the characteristics of wetlands? (fairly basic)

Wetlands are ecosystems which are constantly or recurringly inundated (water covers the surface) or saturated (soil pores are filled with water). They provide seasonal flood storage, reduce peak flows and sequester carbon (a lot of it), and have distinct features, such as hydric soils and hydrophytic vegetation.

What are hydric soils?

Soil that is saturated long enough to develop anaerobic (low oxygen) conditions, and thus distinct chemical and biological processes. (i.e peat → plant matter compressed over thousands of years, unable to decompose due to low oxygen conditions.

What is hydrophytic vegetation?

Plants specifically adapted to live in wet soil; often have channels to transport oxygen to roots, not just taking in energy/oxygen from air.

What are some of the important services wetlands provide?

Improve water quality by filtering water; reduce peak flows by providing flood storage, may sustain dry season with stored water, reduce coastal and fluvial storm damage by dissipating wave energy and stabilizing shorelines, trap sediments/nutrients/carbon, provide habitat fro a broad arrange of fish, bird and other species.

How do wetlands filter water?

They retain and remove nutrients. Wetlands typically have slow water velocities, so metals, nutrients, and sediment tend to settle out. Plants can perform denitrification, releasing it to the atmosphere. However, as plants take up the nutrients, when they die, the nutrients will just end up back in the system.

What does fluvial mean?

Relating to rivers or streams.

How do wetlands reduce storm damage?

Stabilizing shorelines; mangroves prevent coastal erosion. They dissipate wave energy, etc. Data shows wetlands greatly reduce hurricane storm damage.

What is a tidal wetland?

A wetland influenced by ocean tides and coastal water levels

What are the three main types of tidal wetland? Define each

Mangrove swaps → saltwater marshes with salt-tolerant trees; can protect inland areas from storms. Salt marshes → saltwater marshes with soft-stemmed salt-tolerant vegetation; affected by the tides but away from the waves. Tidal freshwater marshes → marshes that support freshwater species but are affected by tides. They don’t get tides?? but have to be used to regular changes in water level.

True or false: wetlands can be wet seasonally or year round, and can be inundated or saturated.

True

What are two seasonally wet wetlands?

Wet meadows → often dry out in late summer because much of their water comes from precipitation. Typically more saturated than inundated. Marshes → can be wet seasonally or year round. They are typically inundated.

What are types of permanently wet wetlands?

Bogs and fens → typically wet year round, keeps their soil in an anaerobic state and leads to peat development. Marshes → can be wet seasonally or year round. They are typically inundated.

Wetlands can be fed by _____, _________, or _______. What is a type of wetland associated with each?

Direct precipitation, overland flow (surface water) or groundwater. Bogs only receive water through direct precipitation, typically have very stagnant water near the land surface + develop peat. Marshes typically get much of their water through surface floodwaters and runoff; typically have fast-flowing water and do not develop peat. Fens usually receive much of their inflow from groundwater. Typically have faster-flowing water than bogs but still develop peat.

Wetlands can support either _____ or ______ vegetation. Which types of wetlands usually have each?

Woody vegetation or soft-stemmed vegetation; woody vegetation is found in swamps, where water usually comes in through surface flow and precipitation. Soft-stemmed vegetation is often found in marshes, which have herbaceous vegetation and water usually comes in through surface flow and precipitation.

Wetlands can have more _____ or _____ soils. What types of wetlands usually have each and how does this relate to peat and pH?

organic, mineral; Organic soils develop peat, mineral soils do not. Organic soils are common in bogs, which have strongly acidic pH and lower nutrient availability, and in fens, which have weakly acidic pH soils and higher nutrient availability. Mineral soils are found in marshes and swamps, which are closer to neutral acidity.

The globe has lost ___ of its wetlands since 1900.

50%

Why are so many wetlands being destroyed?

Fertile soil for farming, urban development, drain for mosquito control, dredging for flood control, spots to dump, stream channelization, harvesting peat

What is the oldest global environmental agreement, and what’s a bit of history about it?

The Ramsar Convention on Wetlands; adopted in Iran in 1971, designated wetlands of international importance to be listed as “Ramsar sites” and conserved. Now has over 172 countries, though major countries are withdrawing.