Types of Rivers, Lakes, Groundwater & Glaciers: A Comprehensive Guide

Posted on Nov 11, 2024 in Geology

Typology of Rivers

1. Rivers in Trenches

These rivers have a steep slope and high speed, which are characteristic of the upper channel and lead to significant erosion.

2. Straight Rivers

Relatively rare, these rivers typically have gravel beds and sufficient capacity but limited sediment load.

3. Braided Rivers

These rivers are characterized by high sediment transport (high energy, capacity, and competence). They have very wide channels relative to their depth and are common in deforested areas.

4. Meandering Rivers

These rivers have a curvy, low-slope profile and exhibit both erosion and sediment deposition.

Lakes

Lakes are part of continental drainage systems. Water flowing from the sea or inland can encounter obstacles, leading to the formation of these bodies of water. Lakes have distinct properties, including water movement and vital ecological functions. Compared to rivers, lakes support a greater diversity of plant and animal life due to their calmer waters.

Lake water movements resemble those of oceans, with wind generating waves in larger lakes. Tides, known as seiches, also occur due to the gravitational pull of the moon and sun. Currents within lakes flow towards their outlets, which can be surface or subsurface (e.g., through cracks or underground channels). Lakes regulate the temperature of their surroundings, acting as thermostats, similar to the rivers that originate from them. They also contribute to atmospheric moisture and influence rainfall patterns. Lakes accumulate both inorganic minerals and organic matter. Humans utilize lakes for transportation, agriculture, recreation, and as a source of water, leading to the creation of artificial lakes.

Lakes are fed by rivers, rainfall, snowmelt, and groundwater. However, lake levels can fluctuate over time, increasing or decreasing over years depending on the inflow and outflow rates. If water loss exceeds water gain, the lake may become saline and its level can drop, potentially leading to complete drying.

Limnology

Limnos means marsh, pond, or lake.

Definitions of Limnology:

  • Forel (1892): Oceanography of the lakes.
  • SIL (1922): Science related to the study of inland waters as a whole.
  • González Bernaldez (1969): The science of continental aquatic ecosystems.
  • Odum (1971): Study of the structure and function of inland aquatic ecosystems.
  • Wetzel (1975): Limnology is broadly the study of functional responses and productivity of freshwater biotic communities in relation to their physical, chemical, and biotic environment.
  • Cole (1988): A segment of Aquatic Ecology.
  • Margalef (1983): Ecology of inland waters.
  • Edmonson (1991): Study of lakes as very complex systems, emphasizing multidisciplinarity.
  • Horne & Goldman (1994): Recalls that inland saline lakes are also part of limnology, particularly relevant in the arid American West.
  • Wetzel (2001): From the perspective of energy flow, emphasizes physical and chemical limnology.

Essentially, the definition of limnology remains consistent with the one adopted in 1922: the study of inland waters, encompassing all types of systems, including lakes, rivers, and wetlands.

Lake Ecosystems

Lake ecosystems are primarily defined by their vertical structure. The distinction between the epilimnion (upper layer) and the hypolimnion (bottom layer) arises from the formation of a thermocline, a layer where water temperature changes rapidly with depth. This leads to stratification of the water body. The epilimnion is typically well-mixed, warmer, and less dense than the hypolimnion.

Lake Drying

Reasons for Lake Drying:

  1. Continental Uplift: When the continental level rises, water drains more quickly, potentially leaving the lake basin dry.
  2. Deforestation: Deforestation reduces moisture retention in and around the lake, leading to decreased rainfall. This occurs because humidity acts as a net, trapping moisture as wind passes through. Without sufficient trees and humidity, wind carries moisture away without forming rain clouds.
  3. Formation of Cracks: Lakes can lose water through cracks in their beds. This can be caused by erosion, particularly if the underlying material is weak, or by earthquakes that fracture the bedrock.
  4. Sediment Accumulation: Sediment carried by rivers can accumulate in lake beds, gradually reducing the lake’s volume and potentially causing it to overflow or drain more quickly. This phenomenon is also linked to erosion, as increased erosion leads to higher sediment loads in rivers.
  5. Urban Growth: Uncontrolled urban expansion has created environmental problems that impact lakes, particularly those near large cities. Pollution is a major threat, affecting lakes like those in Detroit, Buffalo, Salt Lake City, Guadalajara (Lake Chapala), and Mexico City (Lake Texcoco).
  6. Harmful Vegetation: The growth and spread of invasive plant species can harm lakes by inhibiting the development of other plant and animal life. This can be addressed by removing the invasive plants for use as fertilizer or animal feed, or by introducing animals that consume them.

Lakes play a crucial role in natural ecosystems due to their rich biodiversity. However, they are increasingly threatened by human activities.

Groundwater

Groundwater originates primarily from the infiltration of rainwater, river water, lake water, glacial meltwater, and even deep ocean water. It can also be generated by volcanic activity, which releases moisture from within the Earth, or through fossil water, which is water trapped in earlier geological periods between layers of sedimentary rock. Groundwater levels vary by depth and function. Water near the surface is called the zone of aeration, where it is in contact with air and can be further divided into soil water, intermediate water, and capillary water.

Types of Underground Water Bodies:

  1. Aquifers: These are mobile water bodies that can be exploited by tapping into springs or pumping from the surface.
  2. Aquitards: These are less permeable water bodies that are difficult to access and cannot be readily drained or pumped.
  3. Aquicludes: These formations do not hold water but allow it to pass through.
  4. Perched Water Tables: These are smaller, localized water tables that occur above the main water table, often perched on a layer of impermeable rock.

Groundwater returns to the surface through various pathways, including feeding rivers and lakes, transpiration by plants, extraction through wells or tunnels, slow seepage into the ocean floor, and discharge through hot springs and geysers. Hot springs are formed when groundwater comes into contact with magmatic rocks, resulting in elevated temperatures and sometimes high-pressure jets of water known as geysers.

Glaciers

Glaciers are moving masses of ice that cover land. They originate at the snow line, which is the lowest elevation where snow persists year-round. In polar regions, the snow line is at sea level, while in the equatorial zone, it is above 5,000 meters.

Types of Glaciers:

  • Valley Glaciers: These form as ice descends from high mountains, carving out valleys.
  • Continental Glaciers: These cover vast areas of land in polar regions, also known as ice sheets.

Glaciers are powerful agents of erosion and landscape formation. Valley glaciers carve out cirques (bowl-shaped depressions) in mountainous areas and widen valleys into a U-shape. They also deposit rocks and debris, forming moraines. Ancient continental glaciers have left behind numerous depressions that are now occupied by lakes. They also deposited rocks and clay, creating hills and fertile plains in some areas.

Glaciers exist on every continent except Australia. They are a common feature of polar landscapes but become increasingly rare towards the equator, where they are found only on the highest mountain peaks.