Magazine article Geographical

A Short Introduction to Rivers: They're the Lifeblood of Civilisation and the Architects of Many of the Landforms We See around Us, but Rivers Have Also Inspired Art, Facilitated Exploration and Formed National Boundaries

Magazine article Geographical

A Short Introduction to Rivers: They're the Lifeblood of Civilisation and the Architects of Many of the Landforms We See around Us, but Rivers Have Also Inspired Art, Facilitated Exploration and Formed National Boundaries

Article excerpt

TO FLOW OR NOT TO FLOW

The volume of water flowing in a river is dependent on numerous factors, and climate is particularly significant. The rivers with the greatest flows are almost entirely located in the humid tropics, where rainfall is abundant throughout the year. These are the Amazon, the Congo and the Orinoco, each of which discharges more than 1,000 cubic kilometres of water into the oceans in an average year. The mightiest of them all, the Amazon, accounts for nearly one fifth of all the river water discharged into the sea.

Rivers in the humid tropics experience relatively constant flows from month to month, but in more seasonal climate zones, rivers exhibit markedly variable flows. The Indus receives most of its water from the Himalaya, and its maximum summer flow is more than 100 times the winter minimum due to the effect of snowmelt.

Minimum discharge is often zero in rivers that flow largely in areas of high latitude and high altitude, where temperatures fall below freezing for part of the year. In these 'intermittent' rivers, the distinct contrast between minimum flow during the frozen winter and great floods during the summer melt season is regular and predictable.

By contrast, the flow of 'ephemeral' rivers, which are typically found in desert areas, is spasmodic and unpredictable. This is because ephemeral rivers respond to rainfall, which is notoriously difficult to predict in many deserts. One study of a river bed in the northern Negev Desert in Israel showed that on average, the channel contained water for just two per cent of the time, or about seven days a year.

PATHWAYS AND BOUNDARIES

River systems have frequently been used by pioneers to explore new territories, opening them up to trade and eventual colonisation. Movement along rivers was useful to traders, explorers and missionaries from Europe in their penetration of the Americas, Africa and Asia in centuries past. During the colonisation of these new territories, rivers were also commonly used as boundaries because they were the first, and frequently the only, features mapped by European explorers.

The diplomats in Europe who negotiated the allocation of colonial territories claimed by rival powers knew little of the places they were carving up. Often, their limited knowledge was based solely on maps that showed few details, rivers frequently being the only distinct physical features marked.

Today, many international river boundaries remain as legacies of those historical decisions based on poor geographical knowledge because states have been reluctant to alter their territorial boundaries from original delimitation agreements. The historic, and contemporary, importance of rivers as natural barriers is reflected in the fact that no less than three quarters of the world's international boundaries follow rivers for at least part of their course.

ALL IN A NAME

Rivers have had their names appropriated for use as place names all over the world. Cities named after their rivers include the capitals of Russia (Moscow: Moskva River), Lithuania (Vilnius: Vilnia River), Central African Republic (Bangui: Ubangi River) and Malawi (Lilongwe: Lilongwe River). Belmopan, the capital city of Belize, was named after two rivers: the country's longest, the Belize River, and one of its tributaries, the Mopan.

On a larger scale, a number of countries are also named after their major rivers. They include Paraguay in South America, Jordan in the Middle East and Gambia and Senegal in West Africa. The Niger River flows through both Niger and Nigeria. India is named after the Indus River, although it no longer flows through India.

Equally, numerous place names are linked to rivers in less direct ways. Oxford means a crossing place, or ford, used by oxen. Many names of settlements located at the mouth of a river have an equally simple etymology:

Falmouth lies at the mouth of the River Fal. …

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