Understanding Runoff, Rivers, and Water Systems

Posted on Apr 2, 2025 in Geology

• Runoff: The displacement of water across the Earth’s surface.
• River: A continuous stream flowing into other rivers, lakes, or the ocean.
• Channel: The path through which a river flows.
• Flow: The amount of water a river carries, measured in cubic meters per second (m³/s). This is influenced by climate, relief, lithology, vegetation, and human activity. Channel stabilization is important for accurate measurement.
• Absolute Flow: The amount of water flowing past a specific point in the river per second.
• Catchment Area: The area from which a river collects its water.
• River System: The distribution of water along a river throughout the year, originating from the river’s source.
• Storm Flow Regime: Flow regime dependent on rainfall.
• Nival Flow Regime: Flow regime dependent on snowmelt.
• Pluvio-Nival Regime: Flow regime where rain is the dominant factor.
• Nivo-Pluvial Regime: Flow regime where snow is the dominant factor.
• Hydrograph: A graph representing a river’s flow over a year, using the coefficient ‘k’.
• Coefficient k: The average monthly flow divided by the average annual flow. A value less than one indicates a low water year; a value greater than one indicates a flood.
• Drought: A period when a stream’s flow reaches its lowest point.
• Flood: The moment of maximum river flow.
• Basin Slope: The set of catchments draining into the same sea.
• Remontant Erosion: Erosion where a river falls in a cascade, wearing away the land backward.

River Characteristics by Region

• Cantabrian Rivers: High erosive power, abundant flow, and fairly regular regime due to consistent rainfall.
• Atlantic Rivers: Long rivers originating near the Mediterranean and flowing into the Atlantic, with an irregular flow regime.
• Mediterranean Rivers: Short rivers (except the Ebro), prone to eroding deforested hillsides and causing significant summer droughts.

Lakes and Other Water Bodies

• Lakes: Bodies of salt or fresh water accumulated in sunken areas.
• Gaps: Smaller and deeper than lakes.

Lake Formation

• Endogenous Lakes: Caused by internal forces within the Earth.
  • Tectonic Lakes: Formed between blocks invaded by water.
  • Volcanic Lakes: Located in the craters of ancient volcanoes.
• Exogenous Lakes: Caused by external forces such as erosion from ice, water, or wind.
  • Glacial Lakes: Formed from the excavation of ice in glacial cirques.
  • Karst Lakes: Originate in basins created by the dissolution of limestone.
  • Endorheic Lakes: Lakes with scarce water that do not reach the sea, accumulating in depressed areas until evaporation.
  • Farm Lakes: Excavated by wind action on loose rocks and sand.
  • Coastal Lakes/Ponds: Formed when rivers deposit sediments, creating a sand path that closes off the sea.

Other Water-Related Features

• Wetlands: Areas of land covered by a shallow sheet of water.
• Aquifers: Underground layers that collect groundwater seepage from precipitation, accumulating on a permeable layer.

Flora and Vegetation

• Flora: Variety of plant species.
• Vegetation: Number of individuals, their size, and bearing.
• Plant Formation: The combination of flora and vegetation in a given space.
  • Forest: Dominated by large trees.
  • Bush: Dominated by smaller species with thinner trunks.
  • Meadow: Dominated by grasses.
  These formations can transition due to natural conditions (climate change, soil) or human intervention.
  • Primary Forest: Vegetation that grows without human intervention.
  • Secondary Forest: Exploited primary forest that is not replanted, leading to species disappearance.

Plants require temperatures above 0°C to develop, although some have adapted to cold weather. Deciduous trees shed leaves in low temperatures, while others thicken their bark and develop small, hard, or needle-shaped leaves.

• Drought-Tolerant Plants: Plants that can withstand drought conditions.