If you're thinking about buying a retractable awning, consider the value, longevity and cost. Purchasing a retractable deck awning is a big investment. While smaller, less-expensive awnings start at around $500, larger, higher-quality awnings can cost as much as $2,000 or more. Before you make the decision to buy a retractable awning, you should learn as much as possible about their benefits and drawbacks. Here are the top three pros and cons to consider.
Drainage basin (catchment area) is the area which supplies a river system, lake or reservoir with water. The whole area consists of smaller sub-catchments supplying tributaries of the main ri-ver and direct catchments, which drain straight into a lake or main river (Box 3.1).ts purpose is to co-nvey excess water from a drainage basin, which will include the products of weathering and addi-tional loads of solutes produced by man. This pro-perty makes a drainage basin an integrator and its operation is reflected in the quantity and quality of the river run-off.
They are also known as drainage divides because they divide the river system or river basins from other river systems. A watershed is also a term that is being used in the North American region to refer to a water basin which is smaller in size and flows into a smaller outlet such as a stream or wetland.atersheds are considered part of a water basin. In other regions of the world, watersheds are the drainage divides that cut through a river system. While both a river basin and a watershed are land forms, they have different functions in our ecology.