Water — A Precious Resource
"'Water is ESSENTIAL for ALL life. Yet, only about 0.006% of Earth's water is FRESH and ACCESSIBLE for human use. Every drop COUNTS.'"
1. How Much Water Is There on Earth?
Distribution of Earth's Water
| Water Source | Percentage | Accessibility |
|---|---|---|
| Oceans (salt water) | 97.5% | NOT usable for drinking/farming |
| Glaciers and ice caps | 1.75% | FROZEN — not easily accessible |
| Groundwater | 0.69% | ACCESSIBLE (wells, borewells) |
| Surface water (rivers, lakes) | 0.03% | EASILY accessible |
| In atmosphere and soil | 0.03% | Minimal |
'Only about 0.75% of Earth's water is FRESHWATER that is relatively accessible. This tiny fraction must support ALL human, animal, and plant life on land.'
Water Usage
| Use | Percentage (Approximate) |
|---|---|
| Agriculture | 70% |
| Industry | 20% |
| Domestic (drinking, cooking, cleaning) | 10% |
2. The Water Cycle — Nature's Recycling System
Water cycle: The continuous MOVEMENT of water between Earth's surface and the atmosphere.
Steps of the Water Cycle
| Process | Description |
|---|---|
| Evaporation | Water from oceans, rivers, lakes turns into WATER VAPOUR (gas) due to SUN's heat |
| Transpiration | Plants release water vapour through their LEAVES (stomata) |
| Condensation | Water vapour COOLS and forms tiny droplets — creating CLOUDS |
| Precipitation | Water falls back to Earth as RAIN, SNOW, or HAIL |
| Run-off | Water flows over land into rivers, lakes, oceans |
| Infiltration | Water SOAKS into the ground to become GROUNDWATER |
'Water from the oceans continually EVAPORATES, forms clouds, and falls as PRECIPITATION. This is the SAME water that has been cycling for MILLIONS of years.'
3. Groundwater — Water Below the Surface
Groundwater: Water that INFILTRATES (seeps) into the ground and is stored in the spaces between soil particles and rocks.
Key Terms
| Term | Definition |
|---|---|
| Infiltration | Seeping of water INTO the ground |
| Water table | The UPPER LEVEL of groundwater |
| Aquifer | An underground layer of rock or sand that STORES water |
| Spring | When the water table meets the surface — water FLOWS out naturally |
| Well | A hole dug/bored to REACH the water table |
| Recharge | Process of groundwater being REPLENISHED |
Factors Affecting the Water Table
Natural factors: Rainfall, geology, vegetation, topography.
Human factors:
| Factor | Effect on Water Table |
|---|---|
| Deforestation | REDUCES infiltration — less groundwater recharge |
| Excessive pumping | LOWERS the water table (extraction > recharge) |
| Urbanisation | Concrete prevents infiltration — reduces recharge |
| Over-irrigation | Temporary rise but long-term depletion |
| Check dams / percolation tanks | INCREASE groundwater recharge |
4. Depletion of Water Resources
Causes of Water Depletion
| Cause | Explanation |
|---|---|
| Increasing population | More people = more water demand for drinking, sanitation, food |
| Agricultural intensification | Green Revolution increased WATER-INTENSIVE crops (rice, sugarcane) |
| Industrial growth | Factories consume and POLLUTE large amounts of water |
| Climate change | Changing rainfall patterns, more FREQUENT DROUGHTS |
| Wastage | Leaking pipes, open taps, inefficient irrigation |
AP Context: 'Andhra Pradesh is a WATER-STRESSED state. Parts of Rayalaseema (Anantapur, Kurnool, Kadapa) face SEVERE WATER SCARCITY, especially in summer. The Godavari and Krishna rivers are the main sources, but their waters are shared across states.'
Effects of Water Depletion
- Droughts: Insufficient water for agriculture and drinking.
- Drying of wells: Farmers forced to dig DEEPER borewells.
- Land subsidence: Ground sinks when too much water is pumped.
- Saltwater intrusion: In coastal areas, over-extraction allows SEAWATER to ENTER the aquifer, making it saline.
- Crop failure: Lack of irrigation water.
5. Water Conservation — Every Drop Matters
Methods of Water Conservation
| Method | How It Helps |
|---|---|
| Rainwater harvesting | Collecting RAINWATER from rooftops or open areas to recharge groundwater |
| Drip irrigation | Water delivered DIRECTLY to plant roots — MINIMAL wastage |
| Check dams | Small barriers across streams — SLOW water flow, ENHANCE percolation |
| Watershed management | Integrated management of land and water resources in a WATERSHED area |
| Reduce, Reuse, Recycle | Fix leaks, use greywater for gardening, recycle treated water |
| Mulching | Cover soil with crop residue — REDUCES evaporation |
| Sprinkler irrigation | Efficient watering of large areas |
Rainwater Harvesting
'Rainwater harvesting is the COLLECTION and STORAGE of rainwater for DIRECT use or GROUNDWATER RECHARGE.'
Methods:
- Rooftop harvesting: Collect rain from roof → pipe → Filter → Storage tank OR recharge pit.
- Pit/pond method: Dig pits or ponds to COLLECT rainwater that PERCOLATES into the ground.
- Borewell recharge: Direct rainwater into OLD borewells to REFILL aquifers.
AP Context — Krishna-Godavari Water Management
'The KRISHNA and GODAVARI river basins are the LIFELINE of Andhra Pradesh water resources.'
| River | Length in AP | Major Dams | Key Uses |
|---|---|---|---|
| Godavari | ~500 km | Polavaram (under construction), Dowleswaram | Irrigation, drinking water for north coastal AP |
| Krishna | ~350 km | Nagarjuna Sagar, Prakasam Barrage, Srisailam | Irrigation (Guntur, Krishna, Prakasam), drinking water |
Challenges:
- Inter-state WATER SHARING disputes (with Telangana, Karnataka, Maharashtra).
- Silting of reservoirs REDUCING storage capacity.
- CLIMATE CHANGE affecting monsoon patterns.
- GROUNDWATER depletion in coastal aquifers due to over-extraction.
Initiatives:
- Neeru-Chettu (Water-Tree) program: AP government programme focusing on WATER CONSERVATION and TREE PLANTATION.
- Polavaram Project: Multi-purpose irrigation and drinking water project.
- Watershed development in drought-prone Rayalaseema districts.
6. Common Mistakes and Fixes
| Mistake | Why It Is Wrong | Correct Approach |
|---|---|---|
| Ocean water can be used directly for farming | Ocean water is SALINE — toxic to most plants | Desalination is expensive and energy-intensive |
| Groundwater is limitless | Groundwater takes YEARS to recharge; extraction often exceeds recharge | Groundwater is a FINITE resource that can be DEPLETED |
| Rainwater harvesting is only for houses | Can be done at ALL scales — residential, community, industrial | Any building or open area can harvest rainwater |
| Water table is the same everywhere | Water table VARIES with location, season, and geology | Water table depth differs greatly between regions and seasons |
7. AP SSC Exam Focus
| Topic | Marks | Question Type |
|---|---|---|
| Water distribution on Earth | 2-3 | Percentages and sources |
| Water cycle steps | 3-4 | Explain with diagram |
| Groundwater and water table | 2-3 | Factors affecting |
| Water depletion causes | 2-3 | List and explain |
| Conservation methods | 3-4 | Rainwater harvesting, AP context |
| AP: Krishna-Godavari water management | 2-3 | Short notes |
Quick Self-Test
Q1. What percentage of Earth's water is freshwater available for human use? A1. Less than 1% (about 0.75%, primarily groundwater and surface water).
Q2. Explain the water cycle in three steps. A2. 1) EVAPORATION — sun heats water, turning it into vapour. 2) CONDENSATION — vapour cools to form clouds. 3) PRECIPITATION — water falls as rain.
Q3. What is the water table? A3. The upper level of groundwater below the Earth's surface.
Q4. List two causes of water depletion. A4. Increasing population (higher demand) and excessive groundwater pumping (extraction > recharge).
Q5. What is rainwater harvesting? A5. The collection and storage of rainwater for direct use or groundwater recharge, typically from rooftops or open areas.
Q6. Why are the Godavari and Krishna rivers important for AP? A6. They are the main sources of irrigation and drinking water for a large part of Andhra Pradesh, supporting agriculture in the delta regions.
Q7. How does deforestation affect the water table? A7. Trees help water infiltrate the ground. Deforestation reduces infiltration, leading to less groundwater recharge and a LOWER water table.
