Term
| how do we use water in the U.S? |
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Definition
48% thermoelectric power generation
34% irrigation
11% public supply
5% industrial
less than 1%: domestic wells, livestock, mining, aquaculture |
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Term
| how is water used for electric power generation? |
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Definition
water is used for once-through cooling in power generation plants
1/3 water used for this purpose is saline
1kWh electricity requires 37 gallons H2O for fossil fuel plant
1KWh electricity requries 54 gallons H2O for nuclear power plants
1kWh is the amount of electricity used to power 140 W bulb all day long, a pc for 2.5 hours, or a clothes dryer for 15 min |
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Term
| How much of the water on earth is freshwater? |
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Definition
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Term
| where is freshwater found (list from greatest reservoir to smallest) on earth? |
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Definition
Glaciers and snow 24,064 x 10^3 km^3
Groundwater 23,400 x 10^3km^3
Permafrost 300 x 10^3km^3
Lakes 175 x 10^3km^3
Soil moisture 17 x 10^3km^3
Wetlands 17 x 10^3km^3
Water vapor over sea 10 x 10^3km^3
Water vapor over land 3 x 10^3km^3
Rivers 2 x 10^3km^3
Biological water 1 x 10^3km^3
1km^3 = 1kmx1kmx1km or .6mi x .6 mi x .6 mi
the average daily water use accross the USA is 1.5km^3 as of 2000 |
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Term
| what is the largest useful water reservoir? |
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Definition
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Term
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Definition
evapotransporation, transpiration, transport (of water vapor or water), and condensation
[image] |
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Term
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Definition
the amount of flow per unit of time
can be expressed as volume per time, like gallons per minute or liters per second or thousands of cubic kilometers per year
can be expressed as the volume passing through a cross-sectional area per time, which has units of length per time, like millimeters per hour
the ___ of water during rainstorms is usually expressed in units of length per time |
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Term
| How much water evaporates over the ocean each ear? |
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Definition
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Term
| How much precipitation occurs over the ocean each year? |
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Definition
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Term
| How much precipitaion occurs over land each year? |
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Definition
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Term
| How much water evapotranspires from land each year? |
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Definition
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Term
| What is the net runnof from land (in rivers and groundwater) each year? |
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Definition
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Term
| What is evapotranspiration? |
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Definition
it includes two parts: evaporation from surfaces and transpiration from plants (respiration and passive transfer of water up from roots and through stomata)
an important source of water to the landsurface: over half of the rain and snowfall on land has been recycled at least once on land |
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Term
| How do we calculate how much time water spends within a particular reservoir? |
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Definition
to find this, you need to know the size of the reservoir and the rate of flow in or out of the reservoir
residence time = (volume of reservoir) / (flow rate in or out)
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Term
| what is the residence time? |
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Definition
| something with units of time that can be though tof as the time to fill an empty reservoir, or the average time a parcel of water will spend in the reservoir |
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Term
| What are the respective sizes, fluxes, and residence times of: water in the atmosphere, water in rivers, and groundwater? |
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Definition
Water in the atmosphere: 13 x103km3 = size, 502x103km3/yr = flow, 0.025yr or 9.5 days = residence time
Water in rivers: 2 x103km3 = size, 45.5x103km3/yr = flow, 0.044 yr or 16 days = residence time
Groundwater: 23,400x103km3 = size, 30.2x103km3/yr = flow, 775 yr = residence time |
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Term
| How do we calculate how much water is available for use? |
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Definition
Q = P - ET
Q = runoff (Q is commonly used to designate a flux, a rate of flow, in many systems: river discharge, flux of heat etc)
P = precipitation
ET = evapotranspiration |
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Term
| What is the global value for Q (runoff)? |
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Definition
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Term
| What are the current water withdrawls by humans? |
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Definition
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Term
| How much water, of the available potable water on earth, do humans use and why do people talk about water crises/shortages? |
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Definition
| we use only 10% but water resources and human demands for water are not distributed evenly across the globe |
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Term
| Water Scarcity Index (Rws) - definition and equation |
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Definition
the ratio of water withdrawn for human use divided by the renewable water available for human use
Rws = W - S
Q
Rws = water scarcity index
W = total water withdrawn for human use
S = amount of fresh water produced by desalination for human use
Q = available freshwater (runoff) |
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Term
| when is a region considered highly water stressed and why? |
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Definition
when Rws is greater than 0.4
even though this is less than half it's water stressed b/c
1. H2O used for more than just drinking by humans. H2O in rivers needs for riparian communities, fish habitat etc.
2. numbers used in evaluating Rws are annual averages, water delivery in rain and removals for domestic, power, agricluture, and industry all vary in time. a cusion is needed in this annual average to survive drought years or dry seasons |
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Term
| Generally, where is Rws greatest on the globe? |
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Definition
| in highly populated areas |
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