Water management

Category: Grassland, Tundra, and Human Biomes.

Geographic Location: Global.

Summary: Water management is the process of developing, distributing, and managing water resources with the goal of optimizing the use of water resources for balanced needs and reducing negative effects on the environment. Growing human populations and climate change are leading to water scarcity and increased contamination of water resources worldwide.

Water management is the process of developing, distributing, and managing water resources. Water resources are essential to agricultural, industrial, household, recreational, and environmental activities. Almost all these water uses by humans require sources of freshwater. Freshwater is defined as having little dissolved salts or other dissolved solids. Though freshwater is a renewable resource, the world’s supply of readily available, clean freshwater is decreasing and is being put under growing pressure from climate change and global population increase.

The goal of water management is optimizing the use of water resources and reducing negative effects on the environment. In an ideal world, water management balances the competing water demands of human populations for sanitation, drinking, manufacturing, leisure, and agriculture.

Water and Ecosystems

Water resources are an important component of ecosystems. Many biomes are defined by their rainfall and water levels. Tropical rainforest ecology, for example, is highly dependent on its namesake year-round high levels of precipitation and humidity. Water also plays an integral role in ecosystem services. Ecosystem services are benefits that humans derive from natural systems, including a wide range of material resources and processes.

These services fall into four main categories: provisioning, which includes the production of food and water; regulating, which includes the control of climate and disease; supporting, which includes nutrient cycling and crop pollination; and cultural, which includes spiritual and recreational benefits. Water resource use can affect each of these categories of ecosystem services.

As human populations grow, so do pressures on ecosystems and water resources. More than half the world’s wetlands were lost during the twentieth century as a result of human activity and improper water resource management. Surface and groundwater systems are being heavily drawn upon and contaminated. Ocean ecosystems are also being contaminated and overfished. Due to improper water resource management and climate change, deserts are the only ecosystems increasing worldwide, and desertification is a significant global environmental problem.

Water Use

Uses of water can be consumptive, where water afterward is not immediately available for other uses, or nonconsumptive (also called renewable), where water can be put to additional use after it is used. Consumptive uses of water include activities that allow seepage into the ground, evaporation into the air, or incorporation into a product (such as agricultural crops). Nonconsumptive uses include treated sewage that is returned as surface water. The main categories of human water use are agricultural, urban, industrial, household, recreational, and environmental.

Agriculture is the biggest consumer of freshwater resources in the world, using about 70 percent of available water resources, according to data from the World Bank in 2020; a significant percent of that water is used for irrigation in an unsustainable manner, drawing more water than an area can provide in the long term. An estimated 793 gallons (3,000 liters) of water is used to produce enough food to feed one person daily, compared with the 0.5–1.3 gallons (2–5 liters) that one person drinks daily.

The amount of water required to produce food for each person is increasing as people tend toward eating more meat and produce, which are more water-intensive to grow than grains. Agriculture can cause water pollution through use of fertilizers, pesticides, and livestock manure that is then washed into rivers by rainfall.

As of 2020, more than half of the world’s people live in towns and cities, and this proportion is expected to reach two-thirds by 2050, according to the United Nations. Agricultural areas surrounding urban centers must compete for water from the same local supply as the city. Traditional water sources, both ground and surface, are being polluted by urban wastewater. Cities offer the best choice to sell produce, so many farmers are located near urban areas and use polluted waters to irrigate their crops. These polluted waters, depending on the city treatment processes, can pose health hazards when consumed in produce. Urban wastewater is a mixture of pollutants from kitchens, toilets, and rainwater runoff, and contains excessive nutrients and salts, pathogens, heavy metals, trace antibiotics, endocrine-disrupting chemicals, and estrogens.

Developing countries have the least amount of water treatment; according to the World Health Organization (WHO), as of 2020, more than 2 billion people do not have access to safely managed drinking water systems. This includes 1.2 billion people without even basic drinking-water services. Pathogens of greatest concern include bacteria, viruses, and parasitic worms in the water supply. These pathogens can directly affect the health of farmers who come into contact with them, as well as indirectly affect consumers who ingest affected produce.

Contaminated water and produce can carry a variety of pathogens, such as salmonella, cholera, and diarrhea. According to the WHO, as of 2022, diarrhea kills about 297,000 children under the age of five annually and is the second-most-common cause of death in this age range.

According to the Food and Agriculture Organization (FAO) of the United Nations, in 2019, industry used about 19 percent of available water resources for such functions as running hydroelectric dams, thermoelectric power plants, refineries, and manufacturing plants. While industry is not as water-consumptive as agriculture, it can cause a large amount of pollution by discharging wastewater that is tainted with manufacturing chemicals. In addition, plants that use water from rivers and lakes as coolant and return the warmed water directly to the water body can cause damage to ecosystems through temperature changes.

According to the FAO, households were estimated to use 12 percent of the world’s available water. This includes water for drinking, cooking, sanitation, bathing, and gardening. It is estimated that—excluding gardening—one person requires around 13 gallons (50 liters) of water per day for household uses. Drinking water, also called potable water, must be of high quality such that it can be consumed without causing immediate or long-term harm. In most developed countries, water supplies piped into houses are all drinking-water quality, despite the fact that only a small percentage of that water is used for drinking.

Recreational water use makes up perhaps the smallest percentage of water resource use. An example of this type of water management is when reservoirs are used for recreation. Often, water levels are kept higher in reservoirs to allow for recreational activities such as boating, which, while nonconsumptive in nature, might prevent that water from being used by agriculture downstream. Sometimes, the release of water from reservoirs is timed to enhance recreation, such as whitewater rafting downstream of the reservoir. Golf courses use large amounts of water to irrigate their lawns, and also apply large amounts of fertilizers and pesticides that can contaminate water supplies through runoff.

Human use of water resources to augment the environment makes up a very small percentage of overall available water use. Such activities include restoring natural or artificial wetlands and lakes, creating fish ladders to allow the movement of fish around dams, and releasing water from reservoirs to help fish spawn or restore river flow regimes. Again, these uses are mostly nonconsumptive, but may reduce water availability for other needs.

Threats to the Water Supply

There are many difficulties with proper water management, including the fact that sources of water often cross national boundaries. However, water that spans international boundaries has been shown by the International Union for the Conservation of Nature (IUCN) to be a source for cooperation over water issues rather than a reason for conflict. In addition, many nonconsumptive water uses are hard to give financial value to, and are generally difficult to manage. These nonconsumptive uses could include protecting water bodies as habitats for rare species or for ecosystem services, as well as protecting ancient groundwater reserves. Climate change may also affect the availability of freshwater by changing precipitation cycles, melting ice caps, and raising ocean levels.

Other challenges facing proper water management include water scarcity and water contamination. To improve water availability, there is a need to improve data, treasure the environment, reform governance, revitalize agricultural water use so that farmers can increase productivity to meet growing needs for food, control urban and industrial water use, and empower underrepresented people in water management.

During the first decades of the twenty-first century, the Southwestern and Western United States has been facing extreme drought conditions. The drought, combined with the effects of climate change, has dramatically reduced the level of the Colorado River, which provides drinking water for more than 40 million people across seven states and parts of Mexico. With river levels at historic lows, the federal government imposed limits on water usage from the Colorado in August 2022. The government has threatened further cuts in water usage if the states that rely on the river do not reach a deal on curbing their own water usage.

Water Scarcity

Water scarcity is becoming an increasing concern as human populations grow exponentially, and as water use for industry, development, and agriculture for food and emerging biofuels increase. A total of 1.2 billion (20 percent) of the world’s people live in areas of physical water scarcity where there is not enough water to meet demands. A total of 1.6 billion people live in areas of economic water scarcity where there is a lack of investment in water infrastructure or insufficient human capacity to supply the demand for water.

Rainwater harvesting is one potential solution for water scarcity. Rainwater is collected with rooftop harvesting systems, water barrels, or water gardens. Harvested rainwater can then be stored for later use. Rainwater can be used as it is for activities like gardening, or can be treated for consumption as drinking water.

Water recycling, using treated wastewater for additional uses, is another solution to water scarcity. Recycled water is used in a wide range of activities, such as agriculture, landscaping, public parks, golf-course irrigation, cooling water for power plants and oil refineries, processing water for mills, watering plants, toilet flushing, dust control, construction activities, concrete mixing, artificial lakes, and replenishing or recharging groundwater basins. Recycling water is especially useful in water-scarcity areas, but is also used to save cost and energy.

Another type of recycled water is called gray water. Gray water is reusable wastewater from residential, commercial, and industrial bathroom sinks, bathtub shower drains, and laundry-equipment drains. Gray water is generally reused on-site and requires the use of nontoxic, low-sodium soaps to protect vegetation.

Water Treatment

Water treatment is the process of making water more acceptable for its desired use. Water is often treated for use in industry, drinking water, and medicine, as well as to return it to the environment without adverse effect. Treating water generally involves either removing contaminants or reducing them to a satisfactory level.

As stated earlier, water contamination can be harmful to humans through exposure to pathogens, toxins, and chemicals, directly and through uptake into produce. In addition, contaminated water can harm ecosystems and wildlife health. Actions to reduce or remove contaminants in water have the potential to save lives and to improve ecosystems and livelihoods in affected areas.

The multiple-barrier approach to preventing produce contamination involves analyzing the food production process from growth to consumption, looking for where a barrier to contamination might be possible. Such barriers could be safer irrigation practices, on-farm wastewater treatment, actions to kill pathogens, or the implementation of crop washing after harvest in markets and restaurants before sale and consumption.

Treating water to make it safe for drinking can solve both the problems of water scarcity and contamination by making otherwise unusable water safe and available. There are many processes involved in treating drinking water. Solids are separated out using physical means such as settling and filtration, chemical means such as disinfection and coagulation, and biological means such as aerated lagoons, activated sludge, and slow sand filters.

Water is generally pre-chlorinated to control algae and bacteria growth; aerated to remove dissolved iron and manganese; coagulated, sedimented, and filtered to remove solids and particles; and disinfected to remove bacteria. This process varies from location to location based on local water quality, needs, and regulations. To ensure quality for drinking water, its treatment, transport, and distribution are generally highly regulated.

Another type of water treatment involves desalinization, also called desalination, which is the removal of dissolved salts and other minerals from water to make it safe for drinking or irrigation. Desalinization is expensive both in terms of energy and infrastructure, and therefore is considered only in areas where freshwater sources are otherwise limited. Australia, for example, receives little rainfall and relies on desalinization to augment its recycled water supplies.

There are two main types of desalinization, membrane and thermo. Membrane desalinization uses membranes to filter salt out of saline water through reverse osmosis. This uses less energy than the alternative but more widely-used process of thermo or vacuum distillation. Vacuum distillation boils the water to separate it from the salt. To reduce the energy needed to boil the water, vacuum distillation is performed at below-atmospheric pressures, which lowers the boiling point of the water, saving energy and, therefore, money.

Desalinization can have negative environmental effects by killing marine creatures caught in ocean inflow water, and increased temperature and salinity in outflow water returned to the ocean. On the positive side, desalinization sometimes produces table salt as a byproduct.

Sewage treatment has the goal of returning water that was used for household or industrial purposes back to the natural environment without causing adverse effects to the ecosystem. This generally involves removing human waste and chemicals from water that is piped to treatment plants. The process of removing these contaminants is similar to the one used to treat drinking water and involves multiple physical, chemical, and biological steps.

Sewage treatment generally results in the production of a liquid effluent that is safe to dispose into the environment, as well as a solid waste sludge. This sludge is generally treated further and discarded, or is sometimes reused as an agricultural fertilizer. With new advanced technology, it is even possible to reuse wastewater safely as drinking water.

In areas where sewage is not properly treated, or when sewage pipes leak and sewage is released before it reaches treatment, there can be negative effects on the environment. Increased nutrient inputs from organic waste like feces can cause eutrophication in water bodies, leading to algal blooms, low oxygen conditions, and fish die-offs. Contaminants from wastewater can have a diverse range of effects on the ecosystem. Endocrine-disrupting chemicals, such as those found in the form of synthetic estrogens in many pharmaceuticals, can cause reproductive deformities in vertebrates and have even been found to cause intersex individuals among fish and frogs.

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