Springs and Their Classification | Geology Optional for UPSC PDF Download

Definition of Springs

• Springs are natural formations where water from deeper subsurface flows on the earth's surface, creating visible flow.
• The flow is influenced by the position of hydraulic head in a confined aquifer and the elevation of the land surface.

Formation of Springs

• For a spring to form, the water head must be above the land surface.
• Springs can also form above the unconfined aquifer if the water table intersects the ground.
• Water supplied by capillary action is not classified as a spring.

Types of Springs

Artisan Springs

• Formed due to pressure within a confined aquifer and are also known as arising or ascending springs.
• The water in these springs can be deep-seated or shallow:
  • Shallow water is mainly contributed by precipitation.
  • Deep-seated water has a more complex origin, possibly magmatic or sedimentogenic.

Classifications of Springs

Based on Temperature

• Warm Springs: Have an average temperature of 37°C in cold climates.
• Hot Springs: Have temperatures higher than the ambient atmospheric temperature.
• Boiling Springs: Have water temperatures close to boiling point and are also known as thermal springs.

Cool Springs

• Have very cold water temperatures and may be influenced by factors like a sandy bottom or the presence of gas or vapor emissions.

Geysers

• Hot springs that emit steam and hot water, often associated with well-defined openings under pressure.
• Famous locations include New Zealand, Yellowstone Park, and Iceland.

Classification of Springs Based on Flow

• Perennial Springs: Flow throughout the year.
• Intermittent Springs: Active during specific seasons.
• Periodic Springs: Flow for a specific period.
• Ebbing and Flowing Springs: Occur along seashores due to density differences.

Classification of Springs Based on Geomorphologic Control

• Mound and Knoll Springs: Found on mounds in arid climates.
• Pool Springs: Large basin-like structures with water filling.

Classification of Springs Based on Source of Water

• Volcanic Springs: Associated with volcanic activities.
• Fissure Springs: Formed along tectonic lines with fractures.

Shallow Water Spring

• Definition and Classification: Supported by meteoritic water sustained by the hydrostatic head of an aquifer, originating at a relatively shallow depth.
• Types of Shallow Water Springs:
  1. Spring in Porous Rocks: Form when the water table reaches or is above the ground level. Gravity plays a significant role in their flow. Examples: Dimple springs, valley springs, channel springs, and border springs.
  2. Spring in Porous Rock Overlying Impervious Rocks: Water migrates to the surface due to gravity when porous rock overlies an impervious bed. Known as contact springs, categorized into horizontal, incline, and irregular types.
  3. Spring in Porous Rock Between Impervious Rocks: Occurs in porous rock sandwiched between impervious rocks. The movement of water to the surface is influenced by the geological structure.
  4. Spring in Impervious Rock: Found in impervious rock formations where water is brought to the surface due to changes in the slope of the land surface.

Examples and Explanations

• Dimple Springs: Form in depressions on hills where the water table intersects with the surface.
• Valley Springs: Emerge due to abrupt slope changes between flood plains and valleys.
• Channel Springs: Develop in depressions caused by channel deepening processes.
• Border Springs: Arise from gradients in flat alluvial slopes.

Hydrology Concepts

Horizontal Impervious Media: Found in horizontal springs, with three subclasses:

• Gravity Springs: Porous material over an impervious bed, forming a mound where water moves by gravity along the contact line.
• Hardpan Springs: Have a small underlying impervious bed that forces water to rise by gravity in the porous media above. Common in perched aquifers above the normal water table.
• Mesa Springs: The overlying material is hard but porous, containing water that percolates down and moves along the contact line between formations.

Incline Category: Impervious bed with an inclined angle, where water in the porous media is above this surface. Water migrates along the incline surface due to gravity and seeps at the contact point of both media at the lower side. Springs in this category may be termed gravity spring, cuesta spring, or hardpan springs.

Understanding Aquifer Springs

Artesian Springs

• Artesian Dip Spring: Occurs when a pervious bed dips in a way that the upper part receives water to sustain the spring in the lower end. Found in sedimentary layered rocks and intertrappean beds in lava formations.
• Siphon Artesian Spring: Found in folded structures. The porous media acts as an inverted siphon, recharging from the flanks and resulting in springs on the lower side of the structure.
• Unbedded Artesian Spring: Found in formations with irregular bedding. The porous medium receives recharge at the top end, sustaining a spring on the lower side of the unconsolidated deposits.
• Fracture Artesian Springs: Occurs when porous media lies between impervious layers, allowing water flow through fractures in the overlying impervious rocks due to hydraulic pressure.

Spring in Impervious Rocks

• Tubular Springs: Vertical springs where water moves vertically. This type is further divided into three categories based on their characteristics.
• Fracture Springs: Occurs in rocks with secondary permeability or capillary-sized pore spaces, allowing water flow through vertical or horizontal openings.

Solution Springs

• Found in regions where aquifers are enlarged due to the dissolution of rocks by circulating water. These springs require specific formations to exist.
• Good formations for sustaining solution springs include limestone, calcareous rocks, sandstone, and salts.
• Example: Limestone formations are known to sustain solution springs due to their chemical composition.

Lave Tubular Springs

• Situated in volcanic formations where caverns and tunnels are created through igneous intrusion processes.
• Tube-like features are formed from the rapid cooling of lava at the surface, which facilitates the flow of water.
• Example: Hawaii, where lava tubes sustain the flow of water.

Fracture Springs

• Emerges from sheet-like or plate-like geological features such as joints, bedding plains, faults, and columnar joints.
• The water intensity in fracture springs is influenced by the quantity of fractures present in the rock formations.
• Example: Areas with extensive fractures like columnar joints have a high potential for fractured rock springs.