The Truth About Blue Water: Is It Polluted?

Blue water is a type of freshwater that includes water in rivers, lakes, glaciers, polar ice caps, and groundwater. It is a vital resource for drinking water, irrigation, and various other purposes. However, blue water is vulnerable to pollution from a range of sources, including agriculture, industry, and sewage. The pollution of blue water has severe economic, ecological, and human health impacts, and it is important to address this issue through investment in water pollution control technology and sustainable land use practices.

Blue water is fresh surface and groundwater

Blue water is the liquid water available in freshwater lakes, rivers, and aquifers. It is also known as "nonsaline water" and is one of the two types of nonsaline water, the other being green water. Blue water is the fraction of water that is available as drinking water, processing water, and water for irrigation in agriculture. It is also used as a transport medium and for several other purposes.

Blue water is the summation of all water withdrawals for irrigation from aquifers and surface water sources that are evapotranspired during the crop season (ETblue). It is estimated as the difference between the theoretical crop evapotranspiration (ETc) and the effective rainfall. Blue water is the amount of water that does not return to the environment from which it was initially withdrawn. In other words, it is the water that is "lost in evapotranspiration".

According to the Food and Agriculture Organization (FAO), blue water is water from groundwater or surface water. Groundwater withdrawal provides 36% of potable water, 42% of water for irrigated agriculture, and 24% of direct industrial water supply. Blue water is also used for plant production and has to be accounted for in a similar way as green water.

Blue water is vulnerable to pollution. Water quality and availability are leading priorities for the global food and agricultural system. Water quality deterioration caused by nutrient flows from agriculture and a lack of adequate management leads to biodiversity loss.

Blue water sources are vulnerable to pollution

Another example of a polluted blue water source is the Yamuna River in India, which is widely recognized as one of the most polluted rivers in the country. The river is essentially a mammoth urban sewer, with raw and decaying sewage causing methane domes to form on the water's surface. International events, such as the 2016 Olympic Games in Brazil, have brought attention to polluted blue water sources, with promises to invest in treatment options to scrub pollutants and regenerate waterways.

Blue water sources are also vulnerable to pollution from modern agricultural and industrial processes. The water footprint of a product is the volume of freshwater used to produce it, and this includes the blue water footprint, which is the volume of surface and groundwater consumed during the production of a product. The grey water footprint measures the pollution generated during this process, and it is expressed as the volume of water required to assimilate the pollutant load to meet ambient water quality standards.

Blue water footprint indicates the volume of fresh water consumed

Blue water is a type of “nonsaline water” that includes groundwater and surface water. It is used for drinking water, processing water, and water for irrigation in agriculture, among other purposes. The blue water footprint is an indicator of the volume of fresh surface or groundwater consumed in producing goods and services. It is the volume of water evaporated, incorporated into the product, or returned to a different location or time period from where it was withdrawn. This can include the water footprint of manufacturing activities, such as the water footprint of offices, canteens, or horticulture.

The blue water footprint is one of three components of the water footprint, which also includes the green water footprint and the grey water footprint. The green water footprint refers to rainwater consumed, while the grey water footprint quantifies the volume of freshwater required to assimilate the pollutant load per existing ambient water quality standards.

The water footprint of a product is the total volume of freshwater used to produce the product, summed over the various steps of the production chain. It also refers to where and when the water is used. The water footprint of an individual, community, or business is defined as the total volume of freshwater used to produce the goods and services consumed by the individual or community or produced by the business. This includes both direct and indirect water use.

The water footprint concept was introduced in 2002 to provide a consumption-based indicator of water use, in addition to traditional production-sector-based indicators. It is a geographically explicit indicator that shows volumes of water use and pollution, as well as their locations. This information is particularly important given the global issues of water shortages, climate change, and environmental concerns.

Blue water is the water in freshwater lakes, rivers, and aquifers

Blue water is the volume of fresh surface or groundwater consumed in producing goods and services. It is the water that is evapotranspired during the crop season and is estimated as the difference between the theoretical crop evapotranspiration (ETc) and effective rainfall. Blue water is the amount of water that does not return to the environment from which it was initially withdrawn; it is the water that is "lost in evapotranspiration."

The blue water footprint is an indicator of the volume of fresh surface or groundwater consumed in producing goods and services. It includes the water footprint of manufacturing activities and overheads, such as the water footprint of offices, canteens, or horticulture. The direct water footprint can be calculated by measuring the volume of water evaporated, incorporated into the product, or returned to a different location or time period from where it was withdrawn.

Blue water sources can become polluted through various human activities. For example, rainwater that seeps into the earth and becomes groundwater can be contaminated by pesticides and fertilizers from farms and livestock operations, waste leached from landfills, and septic systems. This can render the water unsafe for human use and can be difficult or impossible to remove. Once an aquifer is polluted, it may be unusable for decades or even thousands of years.

It is important to protect our blue water sources from pollution to ensure safe drinking water and maintain the health of our freshwater ecosystems.

Blue water is the water lost in evapotranspiration

Blue water is a type of 'nonsaline water', which includes groundwater and surface water. It is used for drinking water, processing water, and water for irrigation in agriculture, and is also used as a transport medium. Blue water is estimated as the difference between the theoretical crop evapotranspiration (ETc) and the effective rainfall. In other words, it is the water lost in evapotranspiration. Evapotranspiration is the sum of all processes by which water moves from the land surface to the atmosphere via evaporation and transpiration. Evaporation can occur from the soil surface, the capillary fringe of the groundwater table, and from water bodies on land. Transpiration, on the other hand, is the movement of water from the soil to the atmosphere via plants. This occurs when plants take up liquid water from the soil and release water vapour into the air through their leaves.

A study combining two 1 km actual evapotranspiration datasets found that average green and blue water for all land cover types in the conterminous United States (CONUS) over 2001-2015 accounted for nearly 70% and 30% of the total evapotranspiration, respectively. The study also revealed that the magnitude of blue water evapotranspiration gradually declined from west to east, with a greater use of supplemental irrigation in the central and eastern US.

According to another source, approximately 35% of global water resources are available as blue water, while the majority (65%) is available as green water. Green water is water that is bound in the soil and in green plants, and it serves as the basis for agricultural production.

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