Water column

A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediments. Water columns are used chiefly for environmental studies evaluating the stratification or mixing (e.g., by wind-induced currents) of the thermal or chemically stratified layers in a lake, stream or ocean. Some of the common parameters analyzed in the water column are pH, turbidity, temperature, salinity, total dissolved solids, various pesticides, pathogens and a wide variety of chemicals and biota.

The concept of water column is quite important, since many aquatic phenomena are explained by the incomplete vertical mixing of chemical, physical or biological parameters. For example, when studying the metabolism of benthic organisms, it is the specific bottom layer concentration of available chemicals in the water column that is meaningful, rather than the average value of those chemicals throughout the water column.

Hydrostatic pressure can be analyzed by the height of a water column, which effectively yields the pressure at a given depth of the column.

Water crane

A water crane is a device used for delivering a large volume of water into the tank or tender of a steam locomotive. The device is sometimes also called a water column in the United States. As a steam locomotive consumes large quantities of water, water cranes were a vital part of railway station equipment, often situated at the end of a platform, so that water could be refilled during a stop at the station.

Overview

Generally, water cranes consist of an upright steel pipe about 8 to 12 inches (0.20 to 0.30 m) in diameter with a horizontal, pivoting pipe connected to its upper end so as to form a swinging arm. The swinging arm is usually designed to rest parallel to the rails when not in use. Water cranes may be able to deliver up to ten cubic metres (2,600 US gallons) of water per minute.

Water supply

In hilly country, natural streams can be dammed and water fed by gravity to the water crane. In flatter country this arrangement is not always possible, so water may be supplied by a tank next to the crane. Water tanks may vary in volume from 190 kilolitres (50,000 US gal) to greater than 757 kilolitres (200,000 US gal). In some cases a well may be used to supply the water to the tank.