Drowning in Our Irrigation System- Water Use in Agriculture
Posted Aug 3, 2017 | Blog Post
On last week’s blog we examined agricultural runoff, caused by excessive farming irrigation and fertilizer use and how it impacts the health of our marine environments and aquatic ecosystems. This week, we are going to stay on that trend and examine agricultural water use through irrigation, and its impact on the sustainability of our global water supply.
To put the global farming footprint into perspective; agricultural irrigation uses 30 percent of the world’s energy supply and 70 percent of the world’s global water supply. Moreover, population growth, rising income levels, climate change and urbanization will all have major impacts on the global food demand, and in turn, the demand for water and energy resources. As mentioned last week, irrigation has been an integral part of keeping up with the rising global food demand, and will continue to maintain its importance moving forward. However, while irrigation has been critical to the success of the global food supply, it is nonetheless a double edged sword, the dangers of which will be the topic of today’s blog.
Irrigated land represents 25 to 30 percent of the world’s total cultivated land, and yet contributes 40 percent to the world’s total food production. Although this may seem like a very efficient crop yield, when you consider that this 25 to 30 percent of land use requires 70 percent of the world’s total global water consumption to function, these numbers become much more concerning. Furthermore, a large portion of this 70 percent of water is wasted in leaky irrigation systems, wasteful field application methods, and cultivation of thirsty crops not suitable for arid environments. For example, cotton, rice, sugarcane and wheat – the thirstiest crops in the world-make up 58 percent of the worlds irrigated farmland in the nine largest river basins. Rice irrigation fields in the Chinese Yangtze River Basin, the third longest river in the world after the Nile and the Amazon, requires 27, 000 million m2 of water to harvest rice fields twice, in one growing season. This is a huge amount of water use for this region and is leading to an economic water scarcity risk for East Asia by 2025.
Take for example the distribution below of US precipitation-fed land compared to irrigated land use.
In 2012, US irrigated land stood at 7.6 percent of all US cropland and pastureland, and yet accounted for 38 percent of all US national freshwater withdrawals, and 80 to 90 percent of all US water consumption. Although this irrigated land accounted for half of the total crop sales in the US, this land was predominately located in Western arid states such as New Mexico, Texas, California and Colorado and required heavy water use for crop production in highly dry regions.
Although in theory, it looks great that a small amount of land can produce a large amount of crop yield, it’s the lack of sustainability in this system that is contributing to environmental degradation. For example in US Western States, the Rio Grande Basin and the Rio Grade River has been greatly exploited for agriculture irrigation through the creation of dams and aquifer basins, which has severely reduced the downstream flow of the river and allowed saline water to contaminate the freshwater source. By 2025, the five Mexican provinces which border this basin will exhibit physical water stress, which will by proximity impact the US Western States and their agricultural output.
Furthermore, although irrigated land will play a larger role in food production worldwide as a result of growing global food demand, climate change will severely impact water availability and make it more difficult for farmlands to irrigate their crops. To bring the issue home to Canada, 97.6 percent of Canadian cropland is precipitation-fed with irrigation systems sporadically included to make up any rainfall deficits. British Columbia has the highest percentage of irrigated land at 20 percent, followed by Alberta with the largest cropland area irrigated at 64 percent of the Canadian total. Changing precipitation patterns, higher atmospheric temperatures, and an increasing number of extreme weather event s- such as hail, frost and flooding – has increased volatility in farming, and has pushed farmers to rely more and more on irrigation systems to meet demands. Additionally, in the prairies, most of the water for irrigation comes from the snow packs on the Rockies. In recent years, these snow packs have been decreasing in size which depletes water for surrounding ecosystems and in turn, negatively impacts aquatic and terrestrial habitats, and ecological waste removal.
Therefore, we need to invest in water management strategies that increase systems for water-saving efficiency and reuse irrigated water. Some potential strategies include drip irrigation systems and recycled water through drainage systems which, if energy efficient, can be very beneficial. Take for example vertical farming. The TruLeaf Truro farm recycles 70 percent of its water usage through its irrigation system and at their new Guelph farm; they will have 10x the plant output of their Truro farm, while using the same amount of water. This is due to an increased efficiency of their water irrigation system and mirrors the sustainable future of farming, to keep up with the ever growing global food demand.
Let me know what you think about the extent of water use in agriculture. Do you think water resources will be an issue moving forward? Let me know and let’s start a discussion anytime at the TruLeaf Facebook and Twitter pages!