puddle

A puddle in a forest clearing

A water puddle on a Danish beach

A puddle is a small accumulation of liquid, usually water, on a surface. It can form either by pooling in a depression on the surface, or by surface tension upon a flat surface. A puddle is generally considered to be small enough to step over and shallow enough to walk through.

Behavior

Puddles commonly form during rainstorms, and can cause problems for transport, especially when combined with cold conditions to form patches of ice, which are highly slippery and difficult to see. Due to the angle of the road, puddles tend to be forced by gravity to gather on the edge of the road. This causes the notorious 'splash' as cars drive quickly through the puddle, which causes water to be sprayed onto pedestrians on the adjacent pavement. Sometimes, irresponsible drivers will do this deliberately. Such activity is frowned upon, and in some countries can lead to prosecutions for careless driving [1].

Puddles commonly form in potholes in a dirt road, or in any other space with a shallow depression and dirt. In such cases, these are sometimes referred to as mud puddles, due to the fact that mud tends to form in the bottoms, resulting in dirtied wheels or boots when disturbed.

Management

Small puddle with reflection of garages and house

Puddles tend to evaporate quickly due to the high surface area-to-volume ratio, allowing a large number of molecules to be vapourised at once, and as such tend to be short lived. However, due to this property, puddles of chemicals such as bromine, which produce highly toxic vapour, are considered highly dangerous and spills such as this must be dealt with immediately, with emergency evacuation as a common step.

In order to deal with puddles, roads and pavements are often built with a camber (technically called 'crowning'), being slightly convex in nature, to force puddles to drain into the gutter, which has storm drain grates to allow the water to drain into the sewers. In addition to this, some surfaces are made to be porous, allowing the water to drain straight through the surface to the aquifer below.

Recreation

A child in a puddle in Vancouver, Canada

Puddles are often considered a source of recreation by children, who consider jumping in puddles to be an "up-side" to rain.

History

Medieval legend spoke of one man who was desperate to find building materials for his house, so he stole cobblestones from the road surface. The remaining hole filled with water and a horseman who later walked through the 'puddle' actually found himself drowning. A similar legend, of a young boy drowning in a puddle that formed in a chuckhole in a major street in the early years of Seattle, Washington, is told as part of the Seattle Underground Tour.

A children's nursery rhyme records the story of Doctor Foster and his encounter with a puddle in Gloucester.

When Walter Raleigh met Queen Elizabeth I, Raleigh is reputed to have thrown his coat over a muddy puddle to allow the Queen to cross without getting her feet wet. Such activities were once considered to be chivalrous, but are less common nowadays.

Biology

Animals often use puddles either as a drinking source, a bath, or, in the case of some smaller animals (such as tadpoles or mosquito larvae), an entire habitat. Puddles are also vital for bathing birds.

Puddles which do not evaporate quickly can become standing water, which can become polluted by decaying organisms and are often home to breeding mosquitos, which can act as vectors for diseases such as malaria and of more recent concern in certain areas of the world, West Nile Virus.

Swallows use the damp loam which gathers in puddles as a form of cement to help to build their nests. The reduction in the number of puddles in the countryside due to intensive farming and climate change is partially to blame for a decrease in the swallows' numbers.

Physics

In the physics context puddles may refer to where a liquid forms into patches on top of a surface of a solid material.

Small puddles of water on a smooth clean surface have perceptible thickness.

Military

In military terminology, puddles are considered to be "liquid terrain obstacles deprived of tactical importance". In military slang, "the Puddle" may also refer to the Pacific Ocean, much as the Atlantic is referred to as "the Pond".