Understanding River Systems: Characteristics and Elements

Water Diversity: Elements of the River System

Water is an essential element for life, but only 3% is freshwater, with the rest being saline.

The Rivers

Rivers are continuous streams whose flow empties into lakes, other rivers, or seas.

Droughts and Floods

• Droughts: Periods of low flow.
• Floods: Periods of high flow.

Flow Rate

The volume of water in a river is measured in cubic meters per second.

The River Regime

The river regime expresses flow rate. Climate variations and the relief condition the rivers, also influenced by lithology, vegetation density, and human action.

Key Elements Affecting River Systems

1) Flow Rate

Flow is greater at the mouth of the river, where there is little evaporation.

2) Irregularity

This refers to the varying amount of water present in rivers. Rainfall increases or decreases, causing rivers to swell or shrink.

3) Material Transportation

Rivers erode and carry materials. At the beginning, rivers have more strength, leading to greater erosion. Materials are transported and deposited in the final stretch.

Hydrographic Schemes: The Larger Rivers

1) Rivers with Nival Regime

These rivers originate in high mountains. Their flow is higher in spring and summer due to melting snow and lower in winter when water freezes.

2) Rivers of Rain Regime

These rivers are dependent on rainfall.

3) Rivers with Mixed Regime

Located at 2000-2500m, these usually have a higher nivo-storm flow with the thaw in spring. At 1600-1800m, they are usually pluvionival.

Regional River Characteristics

The Rivers of the Cantabrian Side

These rivers are short, numerous, abundant, and regular. They have higher erosion rates but are supported by vegetation.

The Rivers of the Atlantic Coast

These rivers are long and flow through plains, forming gullies on the slopes. Their regime is irregular, with droughts in summer and autumn and floods in spring.

The Rivers of the Mediterranean Side

Excluding the Ebro, these rivers are short, highly erosive, and have an irregular regime with strong summer droughts and winter floods. Water transfer projects are implemented to manage water consumption. Floods are frequent, with rivers often drying up for extended periods.

Balearic and Canary Islands

The Canary Islands lack rivers, and the use of aquifers has caused most streams to disappear.