Water

Composition and Fundamental Nature of Water

  • Water consists of tiny molecules composed of hydrogen and oxygen atoms.

    • Chemical formula: H_2O.

    • Individual molecules are microscopic—invisible even under the most powerful light‐microscope.

  • Pure (distilled) water characteristics:

    • Colorless

    • Tasteless

    • Odorless

Physical Forms of Water on Earth

  • Solid

    • Ice, hail, snow, frost

  • Liquid

    • Oceans, seas, lakes, rivers, rain, dew, fog, mist

  • Gas

    • Steam / water-vapor (the invisible form of atmospheric moisture)

Imagining a World Without Water

  • Prompt for reflection: “What would the world be like without water?”

    • Implied answer: No life, no weathering/erosion, no agriculture, no industry, no ecological cycles.

Global Distribution of Water

  • Total water on Earth:

    • 97\% saline (mostly oceans)

    • 3\% freshwater

  • Breakdown of the 3\% freshwater fraction:

    • Ice (icecaps & glaciers) 76\% (≈ 68.7\% in some charts)

    • Groundwater

    • Deep: 11\%

    • Shallow: 12\%

    • Lakes & Rivers (surface liquid): 0.34\%

    • Atmospheric vapor: 0.037\%

    • Net available for direct human use: < 1 % of all Earth’s water.

  • Fresh-surface-water (liquid) breakdown:

    • Lakes 87\%

    • Swamps 11\%

    • Rivers 2\%

Primary Sources of Water

  • Surface Water

  • Groundwater

Surface Water Details

  • Definition: Water located on Earth’s surface (rivers, lakes, wetlands, oceans).

  • Replenishment & Loss

    • Replenished by precipitation & groundwater discharge.

    • Lost via evaporation, plant transpiration, seepage to groundwater, human extraction, or discharge to seas.

  • Key surface-water bodies (examples)

    • Lakes

    • Ponds

    • Streams

    • Rivers

Groundwater Details

  • Definition: Water stored beneath Earth’s surface in soil pores and rock fractures.

  • Infiltration: Process by which surface water percolates downward through soil/pore spaces.

  • Soil/rock permeability classifications

    • Permeable (allows flow)

    • Impermeable (restricts flow)

  • Typical groundwater sources/structures

    • Open wells

    • Tube wells

    • Artesian wells

    • Infiltration galleries

The Hydrologic (Water) Cycle

  • Continuous exchange of water among atmosphere, land, and living organisms.

  • Key reservoirs/flows (per USGS diagram)

    • Atmospheric storage, ice & snow storage, freshwater storage, oceans, groundwater storage, streamflow, surface runoff.

  • Major processes

    • Evaporation & Evapotranspiration

    • Condensation

    • Sublimation

    • Precipitation (rain, snow, hail, sleet)

    • Snowmelt runoff to streams

    • Infiltration & Groundwater recharge

    • Groundwater discharge & spring flow back to surface/oceans

Three Fundamental Phase Processes (Detailed)

  • Evaporation

    • Solar energy heats liquid water → water vapor.

  • Condensation

    • Rising vapor cools → tiny droplets → clouds.

  • Precipitation

    • Droplet aggregation becomes heavy → falls as rain; if sufficiently cold, converts to snow/hail/sleet.

Water & Living Organisms

  • Human body ≈ \tfrac{2}{3} (≈ 66\%–75\%) water.

  • Essential for cellular functions: nutrient transport, temperature regulation, waste removal.

  • Photosynthesis equation (simplified):
    6CO2 + 6H2O + \text{light energy} \rightarrow C6H{12}O6 + 6O2

Categories of Water Use

  • Consumptive Use (water not returned)

    • Irrigation

  • Partial-Consumptive Use (some return)

    • Domestic, Industrial, Institutional, Public, Fire demand

  • Non-Consumptive Use (water largely returned)

    • Navigation, Recreation, Hydroelectric power, Pollution control (dilution)

Specific Human Uses of Water

  • Irrigation: Supplying water to croplands to enhance growth.

  • Drinking: Necessary for metabolic processes—body ≈ 75\% water during exercise.

  • Washing & Hygiene: Bathing, laundry, sanitation.

  • Firefighting: Extinguishing fires.

  • Industrial Processes: Cooling, cleaning, processing, chemical reactions.

  • Transportation: Shipping via oceans/rivers.

  • Recreation: Swimming, boating, skiing (water-based snow sports), skating.

Consequences of Over-Using Water

  • Rapid population growth + rising agricultural & industrial demand → stress on freshwater supplies.

  • Depletion of aquifers; falling water tables.

  • Escalating inter-state or inter-national water disputes (example: Indian states conflicts).

Rationale for Water Conservation

  • Excessive, unplanned use has depleted reservoirs and ecosystems.

  • Conservation involves policies & actions ensuring water remains a sustainable resource for current & future generations.

Domestic Water-Conservation Strategies

  • Detect & repair household leaks.

  • Close faucets while soaping or rinsing.

  • Use greywater (wastewater) for toilet flushes.

  • Install/maintain overflow valves on rooftop tanks.

  • Avoid over-watering lawns; prefer drought-tolerant species.

  • Minimize unnecessary toilet flushes.

  • Employ sprinkler or drip systems in gardens.

Industrial Water-Conservation Strategies

  • Install onsite wastewater-treatment plants.

  • Reuse cooling-tower water for landscaping/irrigation.

  • Design new processes requiring less water.

  • Recycle water streams between manufacturing steps.

  • Regularly audit equipment for water-use efficiency.

Agricultural Water-Conservation Strategies

  • Adopt drip and sprinkler irrigation (high efficiency).

  • Discourage traditional flooding.

  • Prevent excessive irrigation (match crop water needs).

  • Reduce conveyance losses in canals (lining, maintenance).

  • Construct water-harvesting structures: check dams, khet talawadi, pala, gully plugs.

Self-Assessment / Review Questions

  • Define the water cycle.

  • Identify the primary reservoir for Earth’s freshwater.

  • Explain how the water cycle renews Earth’s freshwater supply.

  • Enumerate everyday human uses of water.

  • List one agricultural, one industrial, and one household water use you experienced today.

Composition and Fundamental Nature of Water

  • Water consists of hydrogen and oxygen atoms (H_2O).

  • Pure water is colorless, tasteless, and odorless.

Physical Forms of Water on Earth

  • Solid: Ice, hail, snow, frost

  • Liquid: Oceans, seas, lakes, rivers, rain, dew, fog, mist

  • Gas: Steam / water-vapor (invisible form)

Global Distribution of Water

  • Total water on Earth:

    • 97\% saline (oceans)

    • 3\% freshwater

  • Breakdown of 3\% freshwater:

    • Ice (icecaps & glaciers): 76\% (approx. 68.7\%)

    • Groundwater (deep & shallow): 11\% + 12\% (23\% total)

    • Lakes & Rivers (surface liquid): 0.34\%

    • Atmospheric vapor: 0.037\%

    • Net available for direct human use: < 1 % of all Earth’s water.

Primary Sources of Water

  • Surface Water

  • Groundwater

Surface Water Details

  • Definition: Water located on Earth’s surface (rivers, lakes, wetlands).

  • Replenishment: Precipitation & groundwater discharge.

  • Loss: Evaporation, transpiration, seepage, human extraction, discharge to seas.

Groundwater Details

  • Definition: Water stored beneath Earth’s surface in soil pores and rock fractures.

  • Infiltration: Surface water percolates downward.

  • Permeability: Permeable (allows flow) vs. Impermeable (restricts flow).

  • Sources: Open wells, tube wells, artesian wells.

The Hydrologic (Water) Cycle

  • Definition: Continuous exchange of water among atmosphere, land, and living organisms.

  • Key Processes: Evaporation, Evapotranspiration, Condensation, Sublimation, Precipitation (rain, snow, hail, sleet), Snowmelt runoff, Infiltration & Groundwater recharge, Groundwater discharge.

Three Fundamental Phase Processes

  • Evaporation: Solar energy heats liquid water $\rightarrow$ water vapor.

  • Condensation: Rising vapor cools $\rightarrow$ tiny droplets $\rightarrow$ clouds.

  • Precipitation: Droplets become heavy $\rightarrow$ fall as rain, snow, hail, or sleet.

Water & Living Organisms

  • Human body: $\approx \frac{2}{3}$ (\approx 66\% - 75\%) water.

  • Essential for nutrient transport, temperature regulation, waste removal.

  • Photosynthesis equation: 6CO2 + 6H2O + \text{light energy} \rightarrow C6H{12}O6 + 6O2

Categories of Water Use

  • Consumptive Use: Water not returned (e.g., Irrigation).

  • Partial-Consumptive Use: Some water returned (e.g., Domestic, Industrial).

  • Non-Consumptive Use: Water largely returned (e.g., Navigation, Hydroelectric power).

Consequences of Over-Using Water

  • Depletion of aquifers, falling water tables.

  • Escalating water disputes.

Rationale for Water Conservation

  • To ensure water is a sustainable resource for current & future generations.

Water-Conservation Strategies

  • Domestic: Repair leaks, close faucets, use greywater, minimize toilet flushes, employ drip systems.

  • Industrial: Onsite wastewater-treatment plants, reuse cooling water, design water-efficient processes, recycle water streams.

  • Agricultural: Adopt drip/sprinkler irrigation, prevent excessive irrigation, reduce conveyance losses, construct water-harvesting structures.