CEN 325: Water Resources Exam 1

What percentage of the world’s water is freshwater?

2.5% of the world’s water is fresh.

What is the largest lake in the world by volume?

Lake Baikal.

How many liters per day does a person need for basic survival?

About 15 Liters.

True or False: The Hadley Circulation assumes that the earth is rotating.

False; Hadley Circulation assumes that the earth is not rotating.

What are small particles made of dust or salt that condensation occurs around called?

Aerosols.

What is the name of the graph that represents rainfall intensity as a function of time?

Rainfall hyetograph.

True or False: A storm intensity with a return period of 10 years will definitely occur once every 10 years.

False.

What is the process of water penetrating soils called?

Infiltration.

What is the process of water changing from liquid to vapor stages?

Evaporation.

True or False: Saturated flow occurs when just some of the voids are filled with water.

False; saturated flow occurs when all voids are filled with water.

Which method usually gives the most accurate answers for calculating evaporation?

Combined method.

What is the term for groundwater that enters a channel that is usually always present?

Baseflow.

What are some assumptions about the unit hydrograph approach?

Excess rain is uniformly distributed throughout the watershed; the watershed is not changing.

True or False: Infiltration rate generally increases with time.

False.

What is Lag Time?

Time between the center of mass of the rainfall and the peak of the hydrograph.

What is Time of Concentration?

Time for a particle of water to travel from the hydrologically most distant point in the watershed to a point of interest.

True or False: A typical CN number for a grassy surface will be less than that for an impervious surface.

True.

Which physical processes can be considered abstractions?

Surface Storage, Interception, Evaporation, Evapotranspiration, Infiltration.

What does P represent in the NRCS Model?

Total Precipitation.

True or False: For dry antecedent conditions, the CN number will be higher than for wetter conditions.

False.

What factors influence the relationship between rainfall and runoff?

Soil properties, land cover, ground slope, watershed geometry.

What is the Vadose Zone?

Pores have a mix of air and films of water.

What is the Water Table?

The upper boundary of the saturated zone.

What is an Aquifer?

Pores filled with water through which water can flow.

What is a Confined Aquifer?

An aquifer located between impermeable layers.

True or False: Darcy’s velocity is usually greater than pore velocity.

False.

True or False: The hydraulic conductivity of sand is greater than that of clay.

True.

Which equation would you use to calculate the flow in an unconfined aquifer?

The Theis equation (for non-steady state conditions).

True or False: Pump tests can determine hydraulic properties of an aquifer by pumping a well at an increasing rate and observing the drawdown.

False.

When a well starts being pumped, what forms around the well?

A cone of depression.