Exam 1 Flashcards
Describe four definitions of drought:
Meteorological, agricultural, hydrological, socioeconomical
meteorological - a departure of precipitation below the norm
agricultural - when soil moisture no longer meets the need of a crop
hydrological - when surfae and subsurface water supplies are below normal
socioeconomical - when physical water shortages begin to affect people
- Explain what causes El Nino and La Nina cycles.
a. El Nino –Weak trade winds cause warmer ocean surface waters moving eastward and reducing
upwelling of water on the West coast of South America. Less water for us.
b. La Nina – Strong trade winds move warm ocean surface waters toward Asia and restore ocean upwelling on the West Coast of South America. More water for us.
- How does the Thermohaline circulation operate and how might this change with global warming?
a. Water freezing at the poles expels salt, and the super-salty, cold water sinks very deeply, causing a global circulation pattern.
b. If global warming causes the freezing to cease, the water currents would dramatically change, thus redistributing heat in novel ways, causing some areas to warm more than normally would given global climate change only.
Cools Europe.
- Reading question: Explain why users of the Colorado River in the Upper basin are affected differently by dust deposition on snow then those who use the river in the lower basin (See Deems et al. 2013).
Because those in the upper basin rely on the delayed and gradual melting of the snow pack as their source of water storage, whereas those in the lower basin rely on Lake Powell and Lake Meade as their water storage.
- Who was John Wesley Powell and how did he want to divide up the west?
- One of the first explorers of the West, reported to DC about conditions in the West
- Suggested that the Western states should be divided up according to watershed boundaries
- From the movie “The Colorado River levels, Lake Powell explained| WATER IN THE DESERT” Discuss how the Upper Basin is obligated to the Lower Basin with respect to flow requirements from the Colorado River and how Lake Powell helps meet those needs.
Due to the Colorado compact of 1922, the upper basin is required to provide the lower basin with 7.5 maf per year. Lake Powell acts as a storage reservoir that allows the upper basin to meet this obligation to the lower basin even in drought years.
- What is “minute 319,” ?”
Minute 319 - allowed for the Colorado River to run into the ocean for the first time in two decades, because an earthquake had fractured Mexico’s irrigation system
- What are the three shades of a silver lining made by Jack Schmidt in the article “Scientists see silver lining in fed’s latest efforts to avoid ‘deadpool’ at Lake Powell”
- Estimates of consumptive use may be overinflated
- There are still abounding opportunities to improve water conservation
- The modified release schedule better resembles the natural flow of the river
- What is the stream order at the mouth/outlet of the watershed below?
First order: smallest streams in the network, have no other streams flowing into them
Second order: two first order streams meeting
Third order: two second order streams meeting
- When a smaller order stream meets a larger order stream, the resulting stream retains the order of the larger stream
Write out and define terms for the expanded watershed budget equation
P - precip
GWi - groundwater flow into the watershed
Q - streamflow from the watershed
ET - Evapotransporation (-)
GWo - Groundwater flow out of the watershed (-)
delta S - change in the amount of storage in the watershed
Describe major storage and fluxes (in the water budget) that occur on land
See week 4 DQ’s
You want to determine the depth of water in the soil that is occupied by plant roots in a watershed. In the area of interest the roots extends down to approximately 150 cm. Soil moisture is assumed to be uniform from 0-150 cm. On June 1st you pull a 20 cm3 sample of soil from the root zone and take it back to the lab and find:
Weight of field soil sample = 35 g Weight of field soil sample after drying = 20 g
What is the volumetric water content of the soil sample?
What is the depth of water in the soil profile?
What is the volumetric water content of the soil sample?
35g-20g = 15g water = 15 cm^3 water / 20cm^3 soil = 0.75
What is the depth of water in the soil profile?
0.75*20 = 15cm
- Describe the steps to directly measure volumetric water content of the soil?
divide weight of water by the volume of the soil
- How does adhesive and cohesive bonds influences plant available water in soil? How does texture modify these influences?
Cohesive bonds cause water molecules to stick to each other. Water molecules held by these bonds only are available to plants. Adhesive bonds occur between water molecules and soil particles. Molecules held by these bonds are not available to plants. As soil particle size decreases, surface area increases, lowering the amount of water available to plants on a water content basis.
- Complete the table below
Condition Water Potential (MPa) Saturated Soil Field Capacity Permanent wilting point Air dry Oven dry
0
- 0.033
- 1.5
- 100
- 1000
- What are SNOTEL sites and what type of measurements do they make at those sites ?
- SNOTEL sites are remote snow condition monitoring stations
- temperature, snow depth, snow weight, solar radiation, precipitation, wid sensor
- What does SWE stand for and how is it measured at the SNOTEL sites (also see pg. 64-65 of your text)
a. Snow Water Equivalent = Density x Snow Depth
b. It’s measured using the snow pillow (snow weight)
- Describe how dust, conifer encroachment, and climate change influence SWE in western watersheds?
a. Dust – It decreases the albedo effect of the snow, so that it absorbs more solar radiation, causing it to melt faster
b. conifer encroachment – More snow is caught on the boughs of conifers and sublimates before ever reaching the soil. Also the conifers use a lot of the moisture that is in the soil
c. climate change – warming temperatures, increased drought may lower SWE in the western watersheds
- Data collected from SNOTEL sites have been used to document impacts from climate change. What are some of the challenges associated with using SNOTEL data to document how changes in climate are affecting SWE and stream flow?
a. Changes in sensors throughout time create unequal data that cannot be fairly compared
b. Many SNOTEL sites have poor quality data, while others have high quality data, but usually data users use them non-discriminately
- Where in the watershed do we have the greatest potential to produce streamflow and why? Explain with respect to field capacity of the soil.
a. The higher elevations. Because their soils are generally shallow, and course textured. They also receive more moisture, so they reach saturation much sooner
b. Riparian areas also, because they are very often saturated, so any additional water added by snow would generate streamflow
- What is the SWE of a snowpack that has a density of 22% and height of 48 inches?
SWE = Density X Snow depth
48 x .22 = 10.56
- On December 5th, 2022, SWE at the Timpanogos Divide SNOTEL site was 4.8 inches. If snow density was estimated at 35%, what is the depth of the snow?
4.8 / .35 = 13.7 inches
- How does wind influence snow accumulation and compaction?
- Wind causes uneven distribution of surface snow
- Wind fractures snowflakes, creating dense, granular snow
- (Fill in the blank) Dendrites are the fastest-growing crystals and tend to aggregate into larger snowflakes that result in ____-density snowpacks at ___ temperatures. In contrast, smaller crystals, such as columns, needles, and plates, tend to accumulate into a __-density snow layer.
low, cold, high
The energy that is available to either ripen a snowpack or to melt snow can be determined with the energy budget equation: M=Wi(1-α)+Wa -Wg+H+G+LE+Hr. Describe each component in the energy budget equation and give an example of how its values can fluctuate
Wi(1-α)- incoming short-wave radiation times the inverse of the albido ratio
M – energy available for snowmelt
Wi – total incoming short-wave radiation
south facing slopes melt faster than N-facing due to lower amounts of short-wave radiation
Time of year impacts shortwave radiation (longer days in summer = more short-wave radiation)
alpha – albedo of snowpack
affected by dust on snow
Wa - incoming longwave radiation
Increased by cloud cover, exposed radiation
Wg- outgoing longwave radiation
snow can hold heat and buffer temperatures during night
H- convective transfer of sensible heat at the snow surface
movement of air of a higher temperature than snow over the snow surface can cause it to melt
G- Conduction at the snow-ground interface
Frozen soils are more likely to hold snow than thawed soils
Important early in the snow season and at the end
LE – flow of latent heat (condensation [+] evaporation or sublimation [-])
Latent heat is the energy released or absorbed as a result of phase change
condensation releases energy (warms), evaporation and sublimation absorb energy (cools)
The snowpack will cool as it sublimates
Calm wind and low humidity can inhibit snow melt on warm days by creating a stable cool layer at the now surface
Hr- advective heat from rain or fog
Rain falling on snow
- How can tree stand density influence snowpack accumulation and persistence (address factors of how trees both decrease and preserve snow packs)?
a. snow accumulated on trees can sublimate before ever reaching the surface, also albido can cause wells around tree trunks
b. Can preserve the show that does make it to the ground by shading it
- List and describe the three snowmelt stages discussed in class?
a. warming phase – absorbed energy raises the average snow pack temperature to point at which the snowpack is nearly isothermal (melting point)
b. ripening phase – absorbed energy is used to melt snow, but the meltwater is retained in the snowpack in pore spaces by surface tension forces, when the pores are full, we say the snowpack is ripened
c. output phase – additional snowmelt will produce water output
