Threats: Population growth, overuse/mismanagement of land, poor agricultural practices, pollution.

71% Earth's surface covered by water.
Availability:
- Saltwater (oceans): 97.5% (not directly usable).
- Freshwater: 2.5%
  - Glaciers/Ice Caps: 1.74% of total (68.7% of freshwater).
  - Groundwater: 0.66% of total (30.1% of freshwater).
  - Surface Water: 0.03% of total (1.2% of freshwater) - lakes (0.007%), rivers (0.0001%), swamps/marshes (0.0008%).
Hydrological Cycle: Solar energy drives evaporation; water returns as rain/snow, passes through organisms, returns to oceans.
Global Water Crisis & Importance of Conservation:
- Limited availability & uneven distribution.
- Increasing demand (population growth).
- Climate change (altered rainfall, melting glaciers).
- Water pollution.
- Cost savings (reduces need for infrastructure).
Over-exploitation of Water Resources:
- Groundwater depletion.
- Lowering of water table, increased pumping costs.
- Reduced surface water supplies.
- Land subsidence.
- Saltwater intrusion in coastal areas.
Sustainable Use of Water Resources:
- Water recycling & reuse.
- Water-efficient appliances.
- Leak detection & repair.
- Rainwater harvesting.
- Desalination (reverse osmosis).
- Watershed management.
- Drip irrigation.
- Drought-resistant crops.
- Permeable pavements.
- Adjust watering schedules.

Water Borne Diseases: Caused by pathogenic microorganisms transmitted by contaminated freshwater consumption.

Disease	Pathogen	Symptoms
Cholera	Vibrio cholerae (bacterium)	Severe diarrhea, dehydration
Typhoid Fever	Salmonella typhi (bacterium)	Fever, abdominal pain, diarrhea
Dysentery	Shigella spp. (bacteria) / Entamoeba histolytica (protozoan)	Diarrhea with blood/mucus, abdominal pain
Hepatitis A	Hepatitis A virus	Jaundice, fatigue, abdominal pain
Giardiasis	Giardia lamblia (protozoan)	Diarrhea, abdominal cramps, nausea

Water Induced Diseases: Caused by parasites/insects (vectors) that spend part of their life cycle in water.

Disease	Pathogen/Vector	Transmission	Symptoms
Schistosomiasis	Schistosoma spp. (parasites)	Contact with freshwater (snails)	Itching, rash, abdominal pa