Feb 28 2011
Today in class we covered why some parts of the world have too little water and what we can do to fix this. Mr. Willard gave us some interesting statistics are the beginning of class about the world’s water use:
Industry Power- 20%
Anyways, there are four main factors/reasons that can lead to too little water. They are:
1. Dry Climate.
2. A Drought, which is a prolonged shortage of water.
3. Dessication of soil.
4. Excess Stress on the amount of water present in one place.
There are four “fixes” for these problems. They are:
1. Dams. A dam is any obstruction placed in a river or stream to block the flow of water so that water can be stored in a reservoir. In addition to helping with low water levels, dams are used to prevent floods, provide drinking water, facilitate irrigation, and generate electricity. The cons of using dams include: habitat alteration, fishery declines, population displacement, sediment capture, a disruption of flooding, and a loss of recreational opportunities.
2. Water Transfer. This is the concept of diverting water from rivers, streams, lakes, and ponds to farm fields, homes, and cities. In class we talked about the Colorado River and how only a trickle of water actually ends up reaching the Gulf of California. The con of this method is an altered ecology at the once fertile lower river and delta. This has changed plant communities, wiped out populations of fish and invertebrates, and devastated fisheries.
3. Groundwater Withdrawal. This is the process of drilling down into Earth and extracting water from an aquifer. There are two types of aquifers: confined and unconfined. Confined aquifers are under high pressure, so there is no extra energy needed to extract the water, while unconfined aquifers require energy for extraction. Today we are extracting water from the ground at a faster rate than water is returning to the ground, which will lead to future problems. The cons of using groundwater are: lower water tables, possible contamination of the water before extraction, and the formation of sinkholes (ares where ground gives way with little warning).
4. Desalination. This is the concept of removing salt from seawater or other salty waters. There are two ways in which this can be achieved. The first being through distillation. This is done by hastening evaporation from sections of ocean water with heat and then condensing the vapor molecules. The second way would be through reverse osmosis. This involves forcing water through membranes to filter out the tiny salt particles. The cons of desalination are: the expensive price, the large input of fossil fuel required, and the salty waste that is leftover.
Also, a cool video on desalination and Spain.