An entire drainage basin is named after the highest order stream found within it, Relationships are also found between: stream order and the number of in a particular drainage basin and can be measured by dividing total length of all. When water falls or ice melts on a slope, some of the water soaks into the ground and some Drainage basins are separated by ridges called divides, which are. A drainage basin, or catchment as it is also called, is the part of the land surface A drainage divide, on either side of which water will flow to separate basins.
Widespread erosion by the ice sheet eroded soil and weathered rock, exposing the bedrock in rock outcrops. Some of these are on the higher ground, near the divide; others may occur in the stream's course, creating falls or rapids.
Glacial erosion on the divide created a depression now occupied by a lake which drains two ways - into the basin and into the adjacent catchment.
Lake in glacial rock-basin: Edited by Alan G. Macpherson and Joyce Brown Macpherson St. Catchments in Newfoundland and Labrador are fairly typical of areas, with resistant strong bedrock, that have been overrun by glaciers. As a result, they have numerous lakes and wetlands and variable slopes.
- Drainage Basins
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Two types of lakes are common: Western Brook Pond, a large lake in Western Newfoundland, is an example. Small ponds can occupy hollows, either eroded in the bedrock by glacial action, or created by the irregular surface of glacial deposits.
Damming due to natural accumulations of glacial, fluvial or marine deposits or even beaver dams may also create ponds. Rock-basin lakes are usually long and narrow, reflecting the local bedrock characteristics e. All the major lakes of the province are of this type. Artificial dams, such as those at Red Indian Lake and Grand Lake on the island's west coast, have enlarged other lakes. The largest of these consists of much of the interior of Asiawhich drains into the Caspian Seathe Aral Seaand numerous smaller lakes.
Some of these, such as the Great Basin, are not single drainage basins but collections of separate, adjacent closed basins.
In endorheic bodies of standing water where evaporation is the primary means of water loss, the water is typically more saline than the oceans. An extreme example of this is the Dead Sea. Importance of drainage basins[ edit ] Geopolitical boundaries[ edit ] Drainage basins have been historically important for determining territorial boundaries, particularly in regions where trade by water has been important. Bioregional political organization today includes agreements of states e.
Hydrology[ edit ] Drainage basin of the Ohio Riverpart of the Mississippi River drainage basin In hydrologythe drainage basin is a logical unit of focus for studying the movement of water within the hydrological cyclebecause the majority of water that discharges from the basin outlet originated as precipitation falling on the basin.
A portion of the water that enters the groundwater system beneath the drainage basin may flow towards the outlet of another drainage basin because groundwater flow directions do not always match those of their overlying drainage network.
Measurement of the discharge of water from a basin may be made by a stream gauge located at the basin's outlet. Rain gauge data is used to measure total precipitation over a drainage basin, and there are different ways to interpret that data.
If the gauges are many and evenly distributed over an area of uniform precipitation, using the arithmetic mean method will give good results. In the Thiessen polygon method, the drainage basin is divided into polygons with the rain gauge in the middle of each polygon assumed to be representative for the rainfall on the area of land included in its polygon.
These polygons are made by drawing lines between gauges, then making perpendicular bisectors of those lines form the polygons. The isohyetal method involves contours of equal precipitation are drawn over the gauges on a map.
Drainage divide - Wikipedia
Calculating the area between these curves and adding up the volume of water is time consuming. Isochrone maps can be used to show the time taken for runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall.
A drainage basin is the source for water and sediment that moves from higher elevation through the river system to lower elevations as they reshape the channel forms.
Ecology[ edit ] The Mississippi River drains the largest area of any U. Agricultural runoff and other water pollution that flows to the outlet is the cause of the hypoxic, or dead zone in the Gulf of Mexico.
Drainage basins are important in ecology. As water flows over the ground and along rivers it can pick up nutrients, sediment, and pollutants.
With the water, they are transported towards the outlet of the basin, and can affect the ecological processes along the way as well as in the receiving water source.
Drainage basin - Wikipedia
Modern use of artificial fertilizers, containing nitrogen, phosphorus, and potassium, has affected the mouths of drainage basins. The minerals are carried by the drainage basin to the mouth, and may accumulate there, disturbing the natural mineral balance. This can cause eutrophication where plant growth is accelerated by the additional material.
Watershed management Because drainage basins are coherent entities in a hydro-logical sense, it has become common to manage water resources on the basis of individual basins.
In New Zealand, they are called catchment boards. Comparable community groups based in Ontario, Canada, are called conservation authorities.