ENVIRON 102 Lecture 10: 3.03.15 (L) Biodiversity Conservation and the Oceans
4 May 2018
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Water Lecture Notes
March 3, 2015
Freshwater is scarce
Freshwater is only 2.5% of water on Earth
Of that 2.5%, 1% is surface freshwater, 20% is groundwater, and 79% is ice caps and glaciers
Spatial variability
Rainfall varies from centimeters to meters per year
Water balance coefficient: rainfall – potential evaporation
Temporal variability
Natural and human influences
Shorter-term variability (El Nino/La Nina)
Role of deforestation
Role of climate change
Variation in climate can mislead us (Powell and the rain follows the plow
Hydrologic cycle
Surface water: lentic, lotic, and wetlands
Lentic systems often created, sometimes removed (e.g., Aral Sea)
Lotic systems often attempt to control (channelize, levees, etc.)
Wetlands – significant acreage lost
Why the loss in acreage?
Groundwater
Water percolates down to level where rock is saturated – aquifer
Rates of movement in aquifer can be very slow (fossil water?)
o Depend on permeability and fracturing in rock or sediment, as well as pressure and input
If rate of utilization exceeds recharge, water table drops or pressure does down
1 in 3 humans relies on groundwater for drinking: 99% of the rural US relies on groundwater for
drinking
Potential for contaminant transport, depletion, subsidence, etc.
Estuaries and Bays: the end of the pipe
Highly productive ecosystems, key breeding/nursery area for many open ocean species
Example: Chesapeake Bay
o In 1914, Baltimore was the last major American city to install sewer lines, but one of the
first to adopt a waste treatment system – why?
o Receives water from multiple states and cities; ongoing major water quality issues
(pollution, nutrients, sediments; long residence time of water); point and nonpoint source
o Along with overharvesting and other problems – 80% loss of fisheries
(imalayan glaciers as the water towers of Asia
Water Usage Figures
Highly variable around the world
Per capita daily use in US is ~5 gallons domestic; > including virtual
250-650 gallons to grow 1 lb rice
3000 gallons for feed to grow cow for ¼ lb burger
Shirt contains 9 ounces of cotton; water to fill 25 bathtubs needed to grow the cotton
Problems with overuse
Rivers run dry
Subsidence
Aquifer depletion fossil water
Seawater intrusion: water use, sea level rise
find more resources at oneclass.com
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Document Summary
Freshwater is only 2. 5% of water on earth. Of that 2. 5%, 1% is surface freshwater, 20% is groundwater, and 79% is ice caps and glaciers. Rainfall varies from centimeters to meters per year. Water balance coefficient: rainfall potential evaporation. Variation in climate can mislead us (powell and (cid:498)the rain follows the plow(cid:499)(cid:524) Water percolates down to level where rock is saturated aquifer. Lentic systems often created, sometimes removed (e. g. , aral sea) Lotic systems often attempt to control (channelize, levees, etc. ) Rates of movement in aquifer can be very slow (fossil water?) Groundwater: depend on permeability and fracturing in rock or sediment, as well as pressure and input. If rate of utilization exceeds recharge, water table drops or pressure does down. 1 in 3 humans relies on groundwater for drinking: 99% of the rural us relies on groundwater for drinking. Potential for contaminant transport, depletion, subsidence, etc. Highly productive ecosystems, key breeding/nursery area for many open ocean species.
