| Water Management | |
|
There are many different issues associated water management. Sometimes resources are large distances from the major areas of demand, so adequate storage and transport systems are needed. Time scales are also important in areas where rain is scarce, generally the rains do not occur when the water is most needed and again storage is essential. Finally there are issues of water quality and treatment, the water must be fit for human consumption. In many countries water run off has been trapped by the use of dams and storage reservoirs, and transfer of water has been achieved using canals, tunnels and underground pipes. These schemes whilst beneficial also have their disadvantages. The benefits and problems associated with dams for example are outlined table 3. The figures 4 a & b below show the Colorado river prior to and after the building of the Hoover dam. One of the major drawbacks with water transfer schemes is that once the water is again flowing to the area of need local users return or continue to work in their old, inefficient wasteful ways, and do not develop new conservation working methods. |
|
 |
 |
| Figure 4(a) River gorge prior to construction | Figure 4(b) The Hoover Dam |
| China is currently planning to construct a dam across the Yangtze River. The "Three Gorges Dam" represents the largest hydroelectric endeavour in the history of the world. The dam would create a reservoir approximately 400 miles long, permanently submerge approximately 150,000 acres, including 1500 factories, at least 160 towns and 16 archaeological sites and require the resettlement of 1.3 million people. The project has generated controversy because of its serious impacts on the ecology and environment in the region and large- scale resettlement required to complete the project. Scientists are particularly concerned with the 100,000 hectares of cropland that will be submerged when China has an increasing reliance on food imports. Sediments that the Yangtze River now supplies to the coastline will also be trapped behind the dam leading to coastal erosion and the loss of wide swaths of China's most productive farmland. | |
| Benefits |
| Flood & Drought control |
| Irrigation |
| Problems |
| Water losses |
| Salinisation |
| Groundwater changes |
| Displacement of people |
| Drowning of Archaeological sites |
| Seismic stress |
| Estuary and nearshore flow circulation |
| Lake infilling |
| Scouring below the dam |
| Erosion of river delta |
| Loss of nutrients |
| Reduced fish catches downstream |
| Spread of water borne disease |
|
In addition piping water away from water rich areas can also lead to a deterioration of the water habitat. Whole freshwater ecosystems are disappearing as rivers and coastlands are developed around the world. In the United States, Florida Bay, most of which lies within the boundaries of Everglades National Park, has undergone dramatic changes since a rapid influx of people into South Florida began in the 1940s. The bay has been transformed from a healthy estuary to a nearly lifeless, hyper-saline lagoon. The extensive system of canals has drained much of the water feeding the everglades "wetland" region and the ecosystem has experienced both a reduction in water as it is diverted at the same time as the Kissimmee river is causing more pollution to flow into the Everglades. Wetland areas carry out natural water purification processes, thus the water traveling from these areas into local aquifers arrives in a cleaner state and when pumped may require less treatment. By damaging areas such as the everglades we lose important habitat, species and this free purifying resource. |
|
Task 4: a) The Aral Sea is a huge lake hidden in the remote deserts of Kazakhstan in central Asia. Investigate this case of poor water resource management, and consider the possible causes of the fivefold increase in throat cancer over the last 30 years seen in the local population.
|