Challenges are ahead in managing the resource.
By Ronald B. Peterson
Irrigation is the artificial process of applying controlled amounts of water to land to assist in the production of crops or the growth of desirable plants. The various methods of irrigation used over the years are all still in use at some level today.
Initially, all water was supplied to plants because of rain and runoff. However, as people evolved, we began to understand the relationship between water, plant growth, and yield. We realized if we provided more consistent water to plants, they would produce better yields. And with that, irrigation was born.
Settlements, communities, and civilizations were centered around the reliable availability of adequate water. Building canal systems to move the water from one area to another, combined with the use of water from natural ponds and lakes or stored in intentionally designed and built retention ponds and reservoirs, made it possible to farm new, previously arid areas and increase the production of crops.
Evidence of the use of irrigation has been verified as early as 6000 BC.
There have been many irrigation methods employed over the years including natural rainfed, commonly called dry land irrigation; surface irrigation, which has been accomplished through the diversion of rainfall, streams, and rivers; and water naturally accumulated in ponds and lakes or retained and stored in manmade reservoirs.
The stored water is then diverted through a canal system to a field where it is used to flood irrigate the field or is directed into small channels or furrows through use of field, drip irrigation, and various versions of sprinklers. Sprinklers are used in many forms and include moveable rows of pipe with sprinklers attached, wheel lines, and center pivot.
It has been determined that more land can be farmed using sprinklers, but there is a significant issue with water loss due to evaporation.
At first the water spray was directed up at an angle to provide maximum coverage. It has been determined, though, that the closer to the ground we keep the spray nozzles, the less water that is lost due to evaporation. Many sprinkler systems now use drop pipes to place the spray head closer to the ground to minimize water loss due to evaporation.
Wells were originally dug or constructed to provide community, domestic, and livestock watering. Water was extracted manually through a pail and a hand-operated lifting device.
Our ability to construct deeper and more productive wells, and then extract the water with pumps which can also pressurize the delivery system including the sprinklers and sprayers, has made it possible to further improve the efficiency of agriculture to produce food.
A Finite Resource
It was not until the 1960s that water was first recognized as a scarce resource.
Water demands have increased since the 1960s because of doubling of the world’s population. This has caused a significant impact to the demands on agriculture for food production. Much of the food we now consume such as fresh fruits, vegetables, and even meat places a high demand on water for their production.
There were 689 million acres of fertile productive land worldwide in 2015; of this 17% was in the Americas. Using current farming methods including irrigation advances, there are currently an estimated 801 million acres of irrigated productive land throughout the world.
Water use in the United States in 2015 was estimated to be about 322 billion gallons per day, 85 billion gallons per day of which was groundwater. Groundwater use in irrigation was estimated to be 57 billion gallons per day, or about 67%. Irrigation is the largest consumer of groundwater.
In 2015, more than 50% of the groundwater withdrawals in the U.S. were accounted for by 12 states (California, Texas, Idaho, Florida, Arkansas, New York, Illinois, Colorado, North Carolina, Michigan, Montana, and Nebraska).
We have become more efficient in our use of water through technological advances in agriculture and irrigation methods, but nonetheless, the demand for water continues to increase on what we now recognize as a finite resource.
I have often heard it said that the greatest wars yet to be fought will be fought over water.
Some of the challenges we face are as follows:
- Increased competition for water rights
- Overdrafting and the resulting depletion of the underground aquifers
-We are now able to withdraw water from the aquifers underground faster than the natural drainage basins can recharge them. Evaporation due to sprinkler irrigation makes this even more critical. This may ultimately lead to permanent loss of aquifer capacity, decreased water quality, and other issues.
- Ground subsidence as a result of the depletion of the aquifer and resulting geological changes related to the subsidence
-Once the ground subsides, the aquifer is changed and no longer has the same water storage capacity, even if replacement recharge water becomes available.
- Under-irrigation or providing only enough water for the plant gives poor salinity control, which can result in an increase in the salinity of the surface soil due to inadequate water movement necessary to carry the salts below plant roots. This makes it necessary to periodically leach the soil to remove the salts.
- Over-irrigation, which wastes water and chemicals, may lead to pollution, and change the drainage dynamics affecting the water table.
We need to be careful moving forward to evaluate the overall impact of any action we take regarding the use of water. To avoid a global water crisis, we will need to manage water so that we can increase productivity to meet the demands for food, while industry and cities find functional ways to use water more efficiently.
Lest We Forget
Successful agriculture is dependent on its farmers having sufficient access to water.
Water is necessary for our existence. We can only live three days without water.
We borrow the earth’s water and other resources from our descendants. Therefore, we need to leave things in better shape than when we found them.
I appreciate my association with the drilling industry, and specifically the groundwater industry, for the opportunities provided to me through being involved with you, dedicated professionals, and members of the National Ground Water Association.
The information contained in this article is from various sources, including reports by the U.S. Geological Survey. I hope you have found it informative and useful. If you have a subject you want me to address, please send me a note to email@example.com.
Ronald B. Peterson has been involved with the drilling industry for more than 40 years. He previously worked for Baroid Industrial Drilling Products and is now with Mountainland Supply Co., a supply company in Orem, Utah. He served as The Groundwater Foundation’s McEllhiney Lecturer in 2015 and was given NGWA’s most prestigious award, the 2013 Ross L. Oliver Award. He can be reached at firstname.lastname@example.org.