Human Use and Impact on Water

How Humans Use Water

• Most of Earth is covered in water, making it essential for all living organisms.
• Humans utilize water for various activities like washing cars, doing laundry, agriculture, recreation, and transportation.
• The largest percentage of water in the United States is used by thermoelectric power plants (49%).
• Irrigation of agricultural crops accounts for 31% of water use.
• Public supply, including houses, uses 12% of water.
• Industry accounts for 4% of water usage.
• Livestock, mining, and aquaculture use less than 4% of the total water.

Human Impact on Water Distribution and Availability

• Most human activities, including irrigating crops, use freshwater, which only makes up 3% of Earth's total water.
• Freshwater sources include groundwater, lakes, rivers, and streams, and their supplies are impacted by the increasing human population.
• Streams and rivers are often dammed, creating reservoirs to store water and control water flow.
• Dams can provide freshwater for recreation, drinking, irrigation, and hydroelectric power, as seen with Lake Mead and the Hoover Dam.
• Dams can increase soil erosion along stream banks.
• Dams can interfere with fish migration and slow river flow, demonstrated by the Colorado River, which is nearly dry before reaching the ocean.
• Groundwater constitutes most of Earth's accessible freshwater and is a vital source for streams, lakes, and wetlands.
• About 20% of daily water use in the US comes from groundwater, accessed through wells drilled into aquifers.
• Aquifers are areas of permeable sediment or rock holding significant water amounts, which flows into wells and is pumped to the surface.
• Precipitation replenishes groundwater; during droughts, reduced groundwater replacement lowers well water levels.
• Water levels also drop if water usage exceeds the replacement rate.
• Aquifers support rocks and soil above; depletion leads to underground empty spaces.
• When aquifers are depleted, the ground collapses creating sinkholes.

How Humans Pollute Earth's Water

• Water pollution becomes more severe with increasing human population and water usage.
• Water moves through the water cycle: evaporation by solar thermal energy, condensation into clouds, and return to Earth as precipitation.
• Runoff reenters water bodies or seeps into the ground, with pollution from various sources impacting water quality.
• Agricultural runoff contains fertilizers, upsetting nutrient balance in water bodies.
• Industrial waste contains toxic chemicals harmful to aquatic organisms.
• Urban runoff contains pesticides, fertilizers, oil, gasoline, bacteria, and viruses, reducing surface and groundwater quality.
• Mining and construction activities also pollute water.
• Runoff from mines is acidic, containing metals that contaminate water supplies and harm aquatic life.
• Oil spills expose aquatic organisms to toxic substances.
• Oil covering water surfaces reduces oxygen levels.
• Runoff from construction sites contains excess sediment, clouding water and reducing sunlight for photosynthetic organisms.

Ocean Pollution

• Ocean pollution harms the physical, chemical, and biological health of marine ecosystems.
• Ocean pollution occurs naturally (e.g., volcanic eruption) and from human activities.
• Only 13% of ocean pollution originates from shipping or offshore mining.
• Land-based pollution including garbage, hazardous chemicals, and fertilizers, enters oceans.
• About 33% of ocean pollution comes from airborne pollutants originating from land.
• Approximately 44% of ocean pollution is from land runoff.
• About 12% of ocean pollution is from trash dumped directly into the ocean.
• Oceans distribute moisture, provide food and income, mineral and energy resources, and affect climate and weather.
• Marine organisms like algae release oxygen into the atmosphere during photosynthesis.
• Marine organisms can absorb poisons from chemical waste, passing it up the food chain.
• Solid waste, excess sediment, and excess nutrients can harm marine life.
• Solid waste, like plastic, entangles animals or is mistaken for food.
• Plastics break into small pieces and collect in gyres, exemplified by the Great Pacific Garbage Patch, which is twice the size of Texas.
• Excess sediments from erosion, increased by deforestation near water bodies, clog filtering structures of marine organisms and block light needed for photosynthesis.
• Excess nutrients, such as nitrogen and phosphorus from fertilizers, cause algal blooms.
• Algal blooms lead to explosive algae growth, with some being harmful and producing poisons.
• Decomposition of large algal blooms consumes oxygen, reducing oxygen levels and harming marine organisms.

Monitoring and Minimizing Human Impact on Water

• Removing pollution from water is difficult and can take decades for groundwater.
• Focus is on preventing pollution from entering the environment.
• The Clean Water Act regulates water pollution sources, including sewage systems.
• The Safe Drinking Water Act protects drinking water supplies nationwide.
• Reducing water pollution can be achieved through laws and individual actions.
• Alternative products without toxins should be used instead of household products containing harmful chemicals.
• Baking soda and white vinegar can be used.
• Less artificial fertilizer or compost can be used on gardens and lawns.
• Dispose of hazardous substances safely, such as motor oil, rather than pouring them into drains or onto the ground.
• Reducing water use helps.
• Take shorter showers, turn off water while brushing teeth, and sweep instead of hosing.