Notes on Water Use, Sources, and Pollution

Kinds of Water Use

• Water use is categorized into four main categories: Domestic, Agriculture, Industrial, In-stream.

Four Categories of Water

• Domestic Use of Water: water used in everyday household activities (drinking, bathing, washing, cooking, etc.).
• Agriculture Use of Water: irrigation and farming processes; agriculture consumes the most water.
• Industrial Use of Water: cooling in power plants, chemical processing, mining, and other industrial needs.
• In-stream Use of Water: uses of water that do not divert it from its source (recreation, hydropower, navigation).

Domestic Water Use

• Global context: according to Sustainable Report 2018, in 2015, 844{,}000{,}000 people or 11\% lacked access to an improved drinking-water source.
• Domestic water use definition: water used in daily household activities such as drinking, bathing, washing, flushing toilets, cooking, watering plants, and feeding animals.

Agricultural Water Use

• Agriculture uses the most water; more than 100\times an average person’s daily needs (conceptual reference).
• About 70\% of the water drawn from surface water and groundwater goes to irrigation.
• Irrigation is a major driver of water demand in agriculture.

Industrial Use of Water

• Hydroelectric power plants require water for cooling.
• Refineries and manufacturing use water for chemical processing and other operations.
• Mining relies on water to extract minerals and fossil fuels, and to facilitate quarrying.

In-Stream Use

• Off-Stream vs In-Stream use definitions:
  • Off-Stream use: uses that require removal of water from its source.
  • In-Stream use: uses of water that do not divert it from its source (recreation, hydropower generation, navigation).
• Today, about 60\% of the world’s largest rivers have been altered to create dams, canals, and other diversion structures.

Water Cycle – Precipitation and Evaporation

• Precipitation: atmospheric water that returns to the surface via rainfall, snow, etc.
• Evaporation: conversion of surface water to water vapor in the atmosphere.
• Pairing exercise (examples from the material):
  • A reservoir dries up after three months of drought → Evaporation
  • A water pump releases enough water after the rain → Precipitation
  • A river overflows after heavy rains → Precipitation

Off-Stream vs In-Stream Use (revisited)

• Off-Stream use refers to domestic, agricultural, and industrial uses that require withdrawal from the water source.
• In-Stream use refers to uses that do not divert water (recreation, hydropower, navigation).

Water Pollution – Concepts

• Water pollution is the contamination of bodies of water by human activities.
• Pollution occurs when pollutants are discharged into a water system, changing its chemical, physical, or biological properties.
• Types: Point Source, Nonpoint Source, Transboundary pollution.

Major Water Pollutants and Their Sources (summary)

• Human and animal wastes: infectious agents; sewage, animal feedlots (agricultural sources)
• Organic chemicals: oil, gasoline, plastics (industrial sources)
• Inorganic chemicals: acids, salts, metal compounds (industrial sources)
• Plant nutrients: nitrates and phosphates (agricultural sources)
• Heat: discharge of heated water (thermal pollution)
• Sediments: erosion and sedimentation affecting aquatic habitats

Pollution Impacts on the Environment and Humans

• Pollutants can cause waterborne diseases and reduce oxygen levels.
• Excess nutrients lead to algal blooms and disruption of food webs.
• Temperature and chemical changes harm aquatic life and ecosystem health.

Human Activities Impacting Water Sources

• Pollution, deforestation, and urbanisation negatively impact water sources.
• Common water sources include rivers, lakes, reservoirs, and groundwater.

Protecting Our Water Sources

• Safeguard water resources for future generations.
• Implement simple conservation actions (reducing waste, protecting watersheds, proper waste disposal).