1. Water cycle terms
a. What is evapotranspiration?
Answer: Evapotranspiration measures the amount of water recycled through evaporation and transpiration. Because they two are difficult to measure independently, they are often measured together and account for the largest proportion of water lost from a watershed.
b. What is a water table? How do rivers relate to water tables?
Answer: The water table is the level that separates saturated soil (where groundwater is located) from unsaturated soil. Rivers are areas where topography falls below the water table so it appears on the surface.
c. What is infiltration? What affects the rate of infiltration?
Answer: Infiltration is the rate at which water is able to enter soil. Factors affecting infiltration include: the amount of precipitation, such as rate, intensity, and duration; soil saturation, such as drier soil absorbing more water than nearly-saturated soil; soil characteristics, like clayey soil absorbing less water more slowly than sandy soils; slope of the terrain, because water moves faster down steeper slopes; and land cover changes, because more vegetation increases transpiration while urbanization creates impermeable surfaces resulting in lower water tables and higher water level peaks in response to precipitation events.
2. Explain human water usage within the context of the hydrologic cycle as a whole. What factors affect our capacity for water usage?
Consumptive uses don't return water to the landscape from which it was drawn, but is rather evaporated or transpired back into the atmosphere. Agriculture usage is consumptive and accounts for a large majority of global water usage. Non-consumptive uses return the water to surface runoff. Most non-consumptive uses, like domestic or industrial usage, return water that is contaminated.
A major factor limiting human consumption is the actual availability of the water for use. A lot of usable water exists in ice, as seasonal precipitation, or in locations far away from human access.
3. What is the definition of water scarcity?
Less than 1,000 m^3 per person per year. The average person needs 1 m^3 of water to drink annually. Other sources (grow food, cleaning, etc.) require orders more water (1,000 m^3 + per person per year).
4) What are the potential effects of watershed deforestation on water and nutrient flows within the watershed?
Removing trees from the watershed would lessen the bank stability and increase erosion, and without the trees to take up any excess nutrients, it will all run into the stream. Also, it would deprive the river's inhabitants of some allocthonous food sources.
5) In what ways is human water usage affected by agricultural practices? How would water flow within the system potentially be different if an agricultural area was forested instead?
When area is tilled to plant crops, the sediment is looser and more likely to be washed into a stream and be deposited in the streambed. Excess nutrients in the fertilizer used on the farm would also leach into a nearby stream. There is also the matter of drawing water from the stream to irrigate the crops-it could potentially decrease the stream flow.