Population growth is the primary cause of water scarcity because it increases the demand for water resources while also contributing to water pollution and contamination.

Natural disasters, such as floods and hurricanes, can cause water pollution, but they are not a major source of ongoing water pollution like industrial waste, agricultural runoff, and sewage discharge.

Drip irrigation is the most effective way to reduce water consumption in agriculture because it delivers water directly to the roots of plants, minimizing evaporation and runoff.

Water conservation is the opposite of water scarcity. It aims to reduce water consumption and increase water availability, not increase water scarcity.

Water treatment is the general term for the process of removing impurities and contaminants from wastewater, which can include water purification, water filtration, and water disinfection.

Rain barrels are not water conservation devices because they collect and store rainwater, which is not part of the public water supply. Low-flow showerheads, dual-flush toilets, and water-efficient dishwashers are all devices designed to reduce water consumption.

Transpiration is the term for the amount of water that a plant loses through its leaves. It is a natural process that helps plants cool down and transport nutrients.

Desalination is the general term for the process of converting saltwater into freshwater. Reverse osmosis, distillation, and electrodialysis are all specific methods of desalination.

Natural pollution is not a type of water pollution because it is caused by natural processes, such as volcanic eruptions and forest fires. Point source pollution, non-point source pollution, and thermal pollution are all caused by human activities.

Capacity is the term for the amount of water that a river or stream can carry without overflowing.

Water rationing is not a type of water conservation method because it involves restricting water use, rather than reducing water consumption through efficient practices.

Nutrient removal is the general term for the process of removing excess nutrients, such as nitrogen and phosphorus, from wastewater. Denitrification, phosphate removal, and biological nutrient removal are all specific methods of nutrient removal.

Physical pollution is not a type of water pollution because it refers to the presence of physical objects, such as trash and debris, in water. Chemical pollution, biological pollution, and radioactive pollution are all types of water pollution that involve the presence of harmful substances in water.

Water reclamation is the term for the process of converting wastewater into a reusable form. Water recycling and water reuse are also terms used to describe this process, but water reclamation is the most comprehensive term.

Water-intensive landscaping is not a type of water conservation method because it involves using large amounts of water for irrigation. Leak detection and repair, water-efficient appliances, and rainwater harvesting are all methods of reducing water consumption.