Share on Facebook Share on Twitter Summary: Water pollution is a global challenge undermining global growth and threatening the world’s freshwater reserves. Agriculture is one of the primary causes for water pollution. Hundreds of millions of people are at risk of being affected by coming in to contact with these polluted waters [14]. Advertisement Water Pollution Facts Water is essential to our very existence, especially the freshwater reserves. However, it is also quite vulnerable to pollution as its a universal solvent i.e. water can dissolve more substances than any other liquid. As a result, toxic substances and waste coming from industries, agriculture and human use can dissolve readily, causing water pollution. Natural calamities like floods, earthquakes, surface run-offs due to rains and winds, oil spills in oceans are also other sources of water contamination [8]. Below diagram highlights the freshwater withdrawals %. Sector-Wise Freshwater Withdrawals % Source: UN Millennium Development Goals Report -2015 UNESCO claims that around 80% of the world’s wastewater is discharged back in the environment without adequate treatment, and since agriculture withdraws the maximum freshwater, it’s also the biggest source of water pollution [6,17]. The 3 biggest sources of water pollution related to agriculture being animal waste, aquaculture production and fertilizers used in agricultural fields. Advertisement Causes

Share on Facebook Share on Twitter Causes of Water Pollution There are many sources of water pollution; however, we’ll be only focussing on agricultural-related pollution sources. Livestock Waste Livestock farming contributes to water pollution in 2 significant ways. 1: Most of the water used for livestock drinking and servicing returns to the environment in the form of liquid manure, slurry and wastewater. The wastewater contains a high amount of total organic carbon (TOC) originating from the use of pesticides, growth hormones, drug residue, antibiotics, blood and animal waste [3]. 2: Surface runoff caused by rain or wind carry all the sediments (soil erosion) along with pollutants (animal manure, chemical fertilizers) from agricultural farms. Advertisement Aquaculture Pollution Breeding fishes for food in a natural environment like oceans and rivers is a risky business. Many types of aquaculture production require chemical treatments for a successful harvest [13]. Quite often, the wastewater from these farms is released directly in the adjacent water bodies which can cause significant water pollution. Furthermore, fish farms generate a substantial mount of pollutants such as fish excretement, uneaten fish food and other organic wastes Pesticide use and on-farm disease can also affect local species [13]. Source: Seafoodwatch.org Since more than 50% of the world’s seafood now comes from aquaculture, the scale of pollution caused due to aquaculture related practices is an important cause of concern [12]. For e.g., In Scotland, the 3rd biggest producer of salmon fish, the discharge of untreated organic waste from salmon production is equivalent to 75 per cent of the pollution discharged by the human population[6]. Soil Erosion Every year 25 billion tonnes of sediments are transported from agricultural fields into the waterways [3]. The topsoil is loosened when land is converted to agricultural lands. Soil can also be loosened due to the hoof action of animals or due to overgrazing vegetation [3]. When that happens, the soil loses its water holding capacity and is eventually washed away into water bodies. Ground Water Pollution Plants need nutrients for growth and survival. Due to increased demand for agricultural products and declining fertility of the soil, the farmlands are fed with tonnes of synthetic fertilizers. The 2 most essential nutrients used for boosting the productivity of the land are Nitrogen and Phosphorous. However, over-fertilization is a bigger problem than under fertilization. When plants cannot absorb all the nutrients from the soil, the nutrients along with other chemical pollutants end up percolating down and polluting the groundwater reserves [1]. Several studies have pointed out that Nitrate is the biggest chemical contaminant of groundwater reserves [1] Advertisement Facts Consequences