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20) About 50% of precipitation over the land infiltrates the surface, of which 75% returns to the
atmosphere via evapotranspiration.
21) On a hot day, a tree can transpire hundreds of liters of water.
22) The water-balance methodology is, in essence, an accounting or bookkeeping system for
water resource analysis.
23) A water budget is derived from measuring system inputs of precipitation and system outputs
of evapotranspiration and runoff.
24) Potential evapotranspiration is a measure of water demand.
25) The highest precipitation values in the United States occur in the Great Plains region.
26) In the United States, evapotranspiration tends to be highest in the southwest.
27) Precise measurements of evapotranspiration are difficult.
28) In easy and fairly accurate method for estimating potential evapotranspiration for most
midlatitude locations utilizes mean air temperature and daylength.
29) Hygroscopic water and gravitational water are available for plant use.
30) Soil moisture deficits are frequently overcome by irrigation in the arid and semi-arid
agricultural regions of the world.
31) At wilting point, no water remains in the soil.
32) Field capacity and wilting point are both influenced by soil texture.
33) Soil and rock that are less than saturated through which gravitational water moves is known
as the zone of aeration.
34) Potential evapostranspiration is a direct measurement of the amount of evapotranspiration
that occurs in a given area during a given period of time.
35) Potential evapotranspiration (POTET), when reduced by the deficit (DEFIC), yields the
actual evapotranspiration value for a given time period.
36) Capillary water is held in the soil against the pull of gravity by surface tension and hydrogen
bonding.
37) Soil permeability depends on soil particle size, shape, and packing of soil grains.
38) Gravitational water is water bound to soil by gravity.
39) The same amount of rain can result in different field capacities depending upon the soil type.
40) There is a single, universally accepted definition of drought scientists use to classify such
events.
41) Socio-economic factors are not considered when evaluating the effects of drought.
42) Meltwater from glaciers and snowpacks provide water for humans in many parts of the
world.
43) Warming temperatures can lead to both increases and decreases in lake levels.
44) There is little evidence to support that changes in the thermal structure of lakes may block
the mixing between surface and deep waters.
45) Human made lakes are generally called reservoirs.
46) The environmental effects of damming rivers for hydropower are minimal.
47) States and countries have constructed networks of pipelines and aqueducts to transfer water
from one geographic area to another.
48) Precipitation is the main source of groundwater, percolating downward as gravitational water
from the soil moisture zone.
49) The difference between a confined and unconfined aquifer is determined by whether there is
solid, impermeable surface beneath the aquifer.
50) A confined aquifer is under the pressure of its own weight, creating a pressure level called
the potentiometric surface to which water can rise on its own.
51) An artesian well, by definition, requires pumping because there is otherwise not enough
pressure to bring the water to the surface.
52) If the water table reaches the surface of the ground, a spring could develop.
53) A stream which receives water flowing from the surrounding aquifer is known as influent,
whereas a streamflow which feeds groundwater is known as effluent.
54) groundwater pollution that our generation creates will persist far into the future (decades to
centuries) because it is virtually impossible to clean an aquifer once it is polluted.
55) Population growth and wasteful water usage threaten to produce water shortages in many
nations of the world.
56) Groundwater represents the largest potential freshwater source on Earth.
57) By current estimates, groundwater provides approximately 25% of the world's irrigation
water.
58) Because groundwater can be recharged through percolation, overconsumption is not
currently a concern.
59) The upper limit of the zone of saturation is known as the water table.
60) An aquifer is an impermeable surface through which groundwater flow is restricted.
61) The general term for the lowering of water table of an aquifer through pumping is the
potentiometric surface.
62) The utilization of aquifers beyond their flow and recharge capacities is known as
groundwater mining.
52
63) The largest sector of daily water withdrawals in the water budget for the United States is
presently that taken for agricultural purposes.
64) The largest known aquifer system in North America is the High Plains Aquifer (Ogallala
Aquifer).
65) The High Plains aquifer irrigates about one-fifth of all U.S. cropland.
66) The water table in the High Plains aquifer has dropped more than 30m (100 ft) in the last five
decades.
67) Desalination removes organic compounds, debris, and salinity from seawater and represents
a method to provide potable water for domestic use.
68) Nonconsumptive water use involves the return of water to its source after use.
69) The permanent removal of water from its source is known as consumptive use.
70) Center pivot agriculture which pumps water from an aquifer is an example of instream water
use.
71) Water resources represent a transboundary resource, with river basins and other water
sources crossing into multiple countries, states, or other jurisdictional boundaries.
72) Both overconsumption and pollution pose issues for water resource management.
73) Water quantity and quality are pressing issues for water resource managers.
74) Water availability per person is expected to increase within the next 50 years.
75) Dams and other water projects result in the redistribution of water over both space and time.
9.3 Essay Questions
1) Describe the location and percentage of all water on Earth. Where are the largest repositories;
where are the smallest repositories?
2) Describe the hydrological cycle, including its different components.
3) Draw and label a diagram of the hydrologic cycle.
4) What are the two basic pathways precipitation can take once it reaches Earth's surface?
5) Define these components of the water budget, explaining the importance of each: precipitation
(PRECIP), potential evapotranspiration (POTET), actual evapotranspiration (ACTET), and soil
moisture storage (STRGE).
6) Define the following: soil-moisture storage, hygroscopic water, wilting point, capillary water,
field capacity, gravitational water, soil-moisture recharge, soil porosity, and soil permeability.
7) Briefly describe the various surface water resources. Which resources are available in your
area? What are the large water projects in your area, such as water transfer projects or dams?
8) Discuss the different aspects of groundwater storage and movement below the surface. Include
the ways in which groundwater comes to the surface on its own, or is drawn to the surface by
humans, along with the consequences.
9) Discuss nonconsumptive use, consumptive use, and instream use as it pertains to the area in
which you live.
10) What are the water issues your community is currently facing? How will these issue likely be
addressed in the future?
