River Systems: Flows and Drainage Basins

• A river is a natural water system flowing from a source to a sea or large body of water
• The channel is the part of a river that holds the water
• Regime describes how the river's discharge changes over time
• Bedload is sediment too heavy to be carried in the water that moves along the bottom
• Sediment consists of soil, sand, and small rock particles moving along the river bed
• The three courses of a river are the upper, middle, and lower course

Hydrological Cycle and Drainage Basins

• Precipitation is any water condensation falling from clouds
• A glacier is a dense ice body constantly moving downhill
• Surface runoff is excess water flow from precipitation or other sources that the soil cannot absorb
• Infiltration is water moving through rock and soil layers
• Percolation is the movement of water through soil
• A drainage basin is an area where all past precipitation collects and drains
• Discharge is the volume of water flowing through a river
• An aquifer is an underground water store
• Mass movement is soil, rock, and water moving downslope due to gravity
• Soil creep is slow, gradual downhill movement of soil and rock particles causing significant landscape changes over time
• Slumping occurs when a section of soil or rock breaks off a steep surface, often due to rain or earthquakes
• Every river has its own drainage basin or catchment area
• A drainage basin is a system with water movement, similar to a small-scale hydrological cycle
• The drainage basin cycle involves stores and flows
• A key difference between a drainage basin and the hydrological cycle is that the drainage basin is an open system with external inputs and outputs
• The amount of water in the basin system varies, whereas the hydrological cycle's water amount remains the same

River Regimes and Hydrographs

• The majority of drainage basins are populated due to fertile soils and the ability to grow food

• Drainage basins receive investments in farmland, homes, businesses, and transport

• Understanding river behavior after heavy rainfall helps assess flood risks

• Rising Limb: Steep increase in river discharge after rainfall

• Peak Discharge: The maximum river flow after heavy rain

• Lag Time: The time delay between peak rainfall and peak discharge, indicating how quickly water reaches the river

• Falling Limb: Gradual decrease in discharge as water drains away

• Base Flow: Normal, steady river discharge before and after a storm

• Storm Runoff: Extra water flowing into the river due to rain, including surface runoff and groundwater flow

Erosion, Transportation, and River Characteristics

• Abrasion occurs when the river load grinds and wears away at the bed and banks

• Solution/Corrosion: Soluble minerals dissolve in slightly acidic water, causing chemical erosion

• Hydraulic Action: The force of water wears away materials from the river bank

• Attrition: Particles collide, breaking into smaller pieces

• Suspension: Fine particles like silt and clay are carried without touching the river bed

• Saltation: Small material moves along the river bed in small jumps

• Solution: Dissolved material is carried

• Traction: Moves large materials like pebbles and rocks

• Upper Course: Steep / narrow and shallow channel / high erosion / rocky bed / fast flow / lower sediment

• Middle Course: Less steep / meanders / floodplain / more transportation and erosion

• Lower Course: Very small steepness / wide & deep channel / meanders and oxbow / floodplain / deposition / mouth

• Oxbow Lake: A lake formed when a meander is cut off from the river

• Meander: A curve in the river caused by erosion and deposition

• V-Shaped Valleys: Steep-sided valleys formed by vertical erosion in the mountains

• Interlocking Spurs: Alternating ridges caused by river erosion in valleys

• Waterfall: A sudden drop in the river

• Gorges: Steep, narrow valley sides caused by river erosion

Water Quality

• Pollution includes waste from industries, agriculture(fertilizers, pesticides), and sewage
• Runoff carries pollutants, chemicals, and sediments into rivers and lakes
• Heavy rainfall increases runoff and erosion, while droughts concentrate pollutants
• Urbanization increases pollution and reduces natural filtration, while deforestation increases sediment
• Warmer water holds less oxygen, affecting aquatic life and increasing bacterial growth
• Acid rain and industrial waste alters pH levels, harming ecosystems
• Erosion from deforestation or construction increases sediment, reducing water clarity
• Excessive water use for agriculture or industry lowers water levels and concentrates pollutants