Course:EOSC311/2020/Conservation of Modern Agriculture

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Geological Influence on Natural Resource Conservation

Natural resource conservation is a field of science aimed at preserving and protecting all aspects of the natural world. Including but not limited to wildlife, forests, rivers, oceans and land. Natural resource conservation is an interdisciplinary field, drawing from numerous disciplines such as economics, forestry, biology, ecology and soil science. One of these disciplines that's importance in conservation cannot be understated is geology. Geology is intertwined in the study of natural resource conservation and can be applied to almost any current conservation issue in some shape or form. In order to protect or sustainably use our resources, it is important to first understand the complex geographical phenomena that led to its existence in the first place. Understanding these geographical phenomena can help inform conversationalists and aid in the formation of potential solutions or important decisions. In essence, this page explains why geology is so important to the field of conservation. In order to evaluate and understand the problem, geological phenomena must be understood in depth before conservationists can provide protection or solutions. In this wiki post I will discuss what groundwater is, its importance in modern agriculture and how anthropocentric influences are contributing to declines in groundwater health and abundance. I will also discuss possible solutions to groundwater issues, particularly pertaining to agricultural use. As someone studying natural resource conservation this topic is very important to me. An extremely large percentage of the world relies on groundwater for not only drinking water but also for food. Protecting this resource is essential and if we as humans want to continue to consume at such high amounts there must be some sort of change.

Groundwater

What is Groundwater?

Confined and Unconfined Aquifers

Simply put groundwater is water held underground in crevasses, pores in rocks or held in soil. Groundwater can come in many forms including soil moisture, permafrost and oil formation water however, the largest and most important form of groundwater comes is aquifers[1]. Aquifers are bodies of water-saturated sediment or rock below the surface of the earth, which can come in three forms, confined, unconfined and perched.

Confined Aquifers

Confined aquifers is a collection of saturated water that exists both below and above layers of impermeable rock. These aquifers can neither attain or lose water from sources above or below them and instead gain water from sources further away from the aquifer where permeable layers exist[1]. Due to their lack of permeability, pressure can build substantially in confined aquifers. This is what allows man made wells to draw water above the natural water table and closer to the surface of the earth, reducing the amount of pumping required.[1]

Unconfined Aquifers

Unconfined aquifers on the other hand are aquifers that have a permeable layer of rock or soil, which allows water to seep directly into the aquifer from the ground surface. Alike confined aquifers, unconfined aquifers have a permeable layer of rock at the base of the aquifer. This is what determines the depth of the aquifer and the location of the corresponding water table.[1] The water table is, defined as the depth at which sediment is saturated with water.[1] The water table can vary depending on topography, climate and season, but is most strongly influenced by the location of permeable rock below the surface.[1] Unconfined aquifers are often the most ideal aquifers for agriculture as they are often large in size and close to the surface making them easily extracted.

Perched Aquifers

Similar to unconfined aquifers, perched aquifers are aquifers that have a permeable ceiling and an impermeable base.[2] However, perched aquifer are much smaller aquifers that exists at depths above the water table, where they accumulate on localized low-permeability or impermeable strata[2]. This creates a smaller local aquifer that is detached from the regional water table and much closer to the surface.[2]

The Importance of Groundwater in Modern Agriculture

Groundwater representing an estimated 97% of all fresh water and 0.061% of all water on earth.[3] It's large abundance has been essential in the growth of many societies and nations, providing drinking water and allowing large scale agricultural production and economic growth. Agriculturally speaking groundwater is the perfect commodity, providing numerous unique benefits like no other commodity can. Groundwater is available directly on demand unlike any other natural source of water, allowing for pressurized irrigation and high productivity, precision agriculture at low capital cost.[4] As a result, groundwater has been exploited globally and has become one of the most important resources in the world, aiding in the growth of modern agriculture. Globally, 70% of known aquifers are used exclusively for agriculture, with almost 40% of all agricultural land being 'waterwell equipped". [4][5] Since 1960, India has increased groundwater irrigated area by 500%, utilizing approximately 90% of its groundwater for agriculture, at an estimated 226‬ cubic kilometres of water per year on agriculture. [4][5] China, the second largest user of groundwater, utilizes 54% of their groundwater for agriculture at around 60 cubic kilometres of water annually for agriculture.[5] In North America, groundwater usage follow similar trends, with 71% and 64% of all ground water being used for agriculture in the U.S and Mexico respectfully.[6] Canada diverts much less of its groundwater to agriculture then the aforementioned countries at only 43% of groundwater, however a staggering 89% of Canadian agriculture rely on groundwater to feed their crops.[6] It's clear that much of the world has become reliant on groundwater as a resource and with ever-growing populations and increasing extraction, fears of aquifers 'drying up' are becoming more and more imperative. However before we can discuss possible steps to circumvent future water shortages, it is important to understand the problems around groundwater usage in detail.

The Issue

The Ogallala aquifer size and saturated thickness as of 1997

Groundwater Recharge Rate

The most pertinent and obvious issue to groundwater security is how much is available to extract and how long it will last us. Currently there is an estimated 22.6 million cubic kilometres of groundwater on earth with anywhere from 1% to 6% of that total located close enough to earths surface to be available for agriculture use.[7] Despite large knowledge gaps on potentially undiscovered aquifers, we can however accurately predict how long existing aquifers will last. This is done by taking into account the groundwater recharge rate current, current usage and size.

Groundwater recharge rate is simply the rate at which water from the surface of the earth percolates downwards and enters an aquifer.[8] Groundwater sources can come from any form of precipitation as well as permafrost melt, lakes and rivers. [8] Water will move through the soil at different rates depending on local climate, soil and anthropocentric conditions. Regions with high annual rainfall will result in more water entering the soil and a higher infiltration rate than drier climates.[9] Moreover, climates that have a high annual temperature will promote higher rates of transpiration and evaporation resulting in more water leaving the soil than in cooler climates.[9] Very cold climates may promote the formation of permafrost or year-long snow preventing any percolation. [9] Percolation rates are also largely to do with soil conditions. Soil with high amounts of sand permit the highest recharge rate, due to the large pore space between soil particles. [10]Soil with high amounts of silt have smaller pore spaces than sand, requiring more time to percolate, while clay has the smallest pore space and therefore the slowest percolation. [10]Within soil it is also important to recognize that organic matter and living plants play a role in percolation as well. Organic matter has a strong water holding capacity through adhesive forces. Likewise, Plants uptake a large amount of water through their roots stems and leaves, resulting in lower amounts of percolation. The last factor that has direct impacts on soil permeability is the influence of anthropocentric objects. This can include anything from sidewalks, roads, buildings or essentially any object created by humans that obstructs water from entering the ground. [11] With development of new infrastructures globally, this has started to become more of an issue for water percolation and has shown to change groundwater table patterns in some regions in China.[11] Essentially anthropocentric structures prevent natural percolation, and lead to the re-direction of surface water where it then percolates in different soil, evaporates or is discharged in rivers, lakes or oceans.

Recharge rates vary from aquifer to aquifer, however, no matter the aquifer it is generally regarded as a slow process. Rates can be anywhere from a meter per day to a few centimetres in a century, although, rates of a few feet per month are most common.[1][12] Due to this many near surface usable aquifers can be anywhere from a couple decades to thousands of years old.[13] Yet despite slow recharge rates aquifers are being drained in regions around the world, with extraction rates far surpassing recharge rates. An estimated 14-17% of all food produced with use of groundwater relies on unsustainable mining of groundwater resources and has led to significant decline in major aquifers such as the the upper Guadiana basin of Spain, the Western Sahara and Nubian Sandstone aquifer systems of North Africa, aquifers of the Arabian peninsula along with many more in India, China, Australia and the U.S.A.[14][15] One of these aforementioned aquifers has recently caused many to worry about the food safety of America in the near future as it provides around 30% of all groundwater for irrigation in the United States[16]. This aquifer is the Ogallala aquifer which is located in the high plains of the United States. The Ogallala aquifer is a massive unconfined aquifer around 450,000 km² and is embedded in eight states including South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas.[17] However despite its size, the aquifer has dropped by more than 300 feet in some areas since the 1940's and has experienced a 30% decline in the Kansas portion of the aquifer and at current rates is expected a further 39% decline[18][19]. Protecting and preserving the Ogallala aquifer is essential for agriculture stability in the future. If depleted, it will take around 6,000 years to naturally replenish and will result in a 30% loss of all agriculture in a country with an ever-increasing population.[20][16]

Groundwater Contamination

As the water table on land decreases, the stronger hydraulic pressure in the ocean can cause saltwater to be pulled into the freshwater aquifer on land

Another major issue to groundwater safety is groundwater contamination. Groundwater contamination occurs when pollutants are introduced into groundwater or naturally make their way into groundwater. Some major anthropocentric sources of contamination include septic systems, pesticides, fertilizers, herbicides, uncontrollable hazardous waste, landfills, atmospheric contaminants and leakage from storage tanks of gasoline, oil or chemicals.[2] A collection of these different containment sources have led to the deterioration and loss of many aquifers globally including China who released a statement saying that around 60% of their groundwater was contaminated in 2014.[21] Contamination can also come in natural forms. In coastal areas where groundwater pumping occurs, the higher mineral content and density of saline water, can cause saline water to push inland into groundwater sources due to a higher water pressure. Seawater intrusion risk increases the more that water is pumped and the water table is brought down, caused many issues in coastal communities reliant on groundwater including Florida, Prince Edward Island, Nova Scotia and New Brunswick to name a few.[22][23] Water moving through certain soils and sedimentary rock can also have detrimental effects on groundwater safety as they can pick up compounds such as calcium, magnesium and chlorides which in large concentrations can contaminate groundwater, making it unusable for agricultural or domestic use.[24]

Possible Solutions

With the many growing issues over groundwater availability and security, it is clear that something needs to change in the near future. Although these suggestions only merely scratch the surface, implementing these 5 new technological or policy related changes to groundwater extraction may prevent future shortages and preserve the essential resource for future generations.

  1. Alternative Crop Production. Although this may not be a complete solution, altering crop production in groundwater fed areas can reduce extraction rates significantly. Certain crops require extremely high amounts of water to grow successfully and are draining groundwater faster than necessary. In India, rice represents 59% of all agriculture, despite it requiring 3000 liters of water per kg produced.[25] Alternative food production such as maize, sorghum and millet require much less water while also providing more nutrients per water consumed. Studies found that implementing these alternative grains could reduce 33% of irrigation across the country.[25] Using alternative crops that require less water could make an immense difference if applied to many crops and could help reduce water extraction rates significantly.
  2. Increase Pricing of Groundwater Extraction. As the depth of the water table in aquifers continues to increase, the amount of energy required to pump water to the surface will increase. Of course, this means more money will be required to pay for the increase energy needed to supply pumps. However as long as extraction is economical, there is no disincentive to continually pump groundwater until aquifers become dry. However, a study conducted at the University of California at Davis found that increasing the price of energy used exclusively for groundwater extraction, led to substantial change in farming behavior.[26] With a higher energy price, farmers substituted away from more water intensive crops such as soybeans towards much less water intensive crops like wheat. The study found that increasing energy costs decreased extraction by approximately 63% of the average amount pumped in a year by a farmer.[26]
  3. Artificial Recharge. To increase recharge rates of aquifers, artificial recharge has been implemented in many areas across the globe. Artificial recharge essentially works by redirecting land surface runoff infiltration basins, ponds or canals to increase the recharge rate of aquifers. This can also involve implementing technologies that can recycle wastewater back into the aquifer to reduce unnecessary loss of groundwater.[10] However, it is important to recognize that the process requires a lot of funding, especially at large scales and may not be the most reasonable solution in some situations.
  4. Smart Irrigation Scheduling. Smart irrigation technology was developed by a group of faculties from the University of Florida and the University of Georgia to provide real time irrigation schedules.[27] Using a combination of weather station data, soil probes and specific devices that measure a plant's water uptake this technology can ensure that every plant receives the minimum necessary water required for successful growth.[27] Amazingly, this technology resulted in immense water savings for citrus fruits and tomatoes with a 24% and 33% reduction in cost for production.[27] However, alike artificial recharge, cost for this technology comes at a premium, and would require a large investment if applied at a large scale.
  5. More Strict Guidelines Around Groundwater Contamination. In regard to groundwater contamination more strict guidelines need to be implemented around important known aquifers. Landfills should be designed and maintained away from sensitive known aquifers. Moreover, storage tanks or pipelines containing gasoline, oil or chemicals should contain a non-corrosive backup containment device placed as a safeguard in case of spillage. Fertilizers and herbicides should be directly monitored on agricultural grounds to prevent overuse and leaching into groundwater. Although many of these guidelines already exist, the only real solution to groundwater contamination is to simply become much more strict in regulating these guidelines to prevent pollution, because once polluted, cleaning groundwater and aquifers is virtually impossible.

Conclusions

Geological proficiency is essential to understanding and maintaining modern agriculture. Groundwater has proved to be an essential resource for the agricultural industry, providing the large majority of water for many major crops throughout the world. Geologically understanding the processes that influence the spatial and temporal recharge rates of aquifers is crucial to understanding the underlying issue surrounding groundwater. Through our discussion it has been made clear that without change in agricultural extraction of groundwater, many aquifers will steadily decline in size. Potential technological innovations, policy shifts and alternative crop production have displayed a potentially positive shift to a new form of irrigation. However, these possible solutions must be applied at very large scales, which may be difficult with such large economic barriers. It is also important to recognize that although these solutions may aid in groundwater overuse, the heart of the issue is that we are simply consuming too much. Groundwater as a resource cannot support the current rates of agriculture forever. As long as water is extracted at a higher rate than it is recharged, the water table will continue to fall.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 USGS (2020). "Groundwater and aquifers". United States Geological Survey. Retrieved June 13, 2020.
  2. ↑ 2.0 2.1 2.2 2.3 SDWF (June 12, 2020). "Aquifers". Safe Drinking Water Foundation. Retrieved June 12, 2020.
  3. ↑ NGWA (2020). "Information on Earth's Water". National Groundwater Association. Retrieved June 13, 2020.
  4. ↑ 4.0 4.1 4.2 Global Water Partnership (2017). "Groundwater Resources and Irrigated Agriculture" (PDF). Global Water Partnership. Retrieved June 14, 2020.
  5. ↑ 5.0 5.1 5.2 Margat, Jean (2013). Groundwater around the World: A Geographic Synopsis. London: CRC Press. ISBN 9780429212734.
  6. ↑ 6.0 6.1 Kidd, Joanna (January 4, 2020). "Groundwater: A North American Resource" (PDF). CentOS. Retrieved June 14, 2020.
  7. ↑ Schlander, Zoe (November 17, 2015). "Here's How Much Groundwater We Actually Have Left". Newsweek. Retrieved June 13, 2020.
  8. ↑ 8.0 8.1 Freeze, Allan (1979). Groundwater. New Jersey: Prentice-Hall. ISBN 0133653129.
  9. ↑ 9.0 9.1 9.2 Crosbie, Mccallum, Walker, Chiew, Francis, Russel, James, Glen, H.S (2010). "Modelling climate-change impacts on groundwater recharge in the Murray-Darling Basin, Australia". Hydrogeology Journal. 18: 1639–1656 – via SpringerLink.CS1 maint: multiple names: authors list (link)
  10. ↑ 10.0 10.1 10.2 National Research Council (1994). Ground Water Rechage Using Waters of Impaired Quality. Washington, D.C.: National Academies Press. ISBN 0309074800.
  11. ↑ 11.0 11.1 Zeng, Xie, Yu, Liu, Wang, Zou, Qin, and Jia, Zhenghui, Yan, Shuang, Linying, Peihua and Binghao (2016). "Effects of anthropogenic water regulation and groundwater lateral flow on land processes". Journal of Advances in Modeling Earth Systems. 8 – via AGU.CS1 maint: multiple names: authors list (link)
  12. ↑ American Ground Water Trust (2001). "How Old Is Your Well Water?". American Ground Water Trust. Retrieved June 15, 2020.
  13. ↑ Government of Canada (2013). "Water sources: groundwater". Government of Canada Website.
  14. ↑ Consultative Group on International Agricultural (June, 2017). "Building ResilienceThrough Sustainable Groundwater Use" (PDF). CGIAR. Retrieved June 14, 2020. Check date values in: |date= (help)
  15. ↑ Cross, Laban, Paden, Smith, Katharine, Peter, Mary, Mark (2016). Spring : managing groundwater sustainably. Gland, Switserland: International Union for Conservation of Nature. ISBN 978-2-8317-1789-0.CS1 maint: multiple names: authors list (link)
  16. ↑ 16.0 16.1 United States Department of Agriculture (2016). [file:///C:/Users/Sam/Downloads/ogallala-final-07102017%20(2).pdf "Ogallala Aquifer Initiative: 2016 Progress Report"] Check |url= value (help) (PDF). United States Department of Agriculture. Retrieved june 14, 2020. Check date values in: |access-date= (help)
  17. ↑ Mcguire, V.L. (2007). "Changes in Water Levels and Storage in the High Plains Aquifer". Geological Survey Fact Sheet: 2007–3029.
  18. ↑ Genoways, Ted (2017). This Blessed Earth: A Year in the Life of an American Family Farm. New York: W. W. Norton & Company. ISBN 0393292576.
  19. ↑ Steward, Bruss, Yang, Staggenborg, Welch, Apley, David, Paul, Xiaoying, Scott, Stephen, Michael (2013). "Tapping unsustainable groundwater stores for agricultural production in the High Plains Aquifer of Kansas, projections to 2110". National Academy of Sciences. 110 – via PNAS.CS1 maint: multiple names: authors list (link)
  20. ↑ Plumer, Brad (2012). "Where the world's running out of water, in one map". The Washington Post. Retrieved June 14, 2020.
  21. ↑ Kaiman, Jonathan (2014). "China says more than half of its groundwater is polluted". The Guardian. Retrieved https://www.theguardian.com/environment/2014/apr/23/china-half-groundwater-polluted. Check date values in: |access-date= (help)
  22. ↑ Prince Edward Island Department of Environment, Labour and Justice (2011). "Salt Water Intrusion and Climate Change: A primer for local and provincial decision-makers" (PDF). Prince Edward Island. Retrieved June 15, 2020.
  23. ↑ United States Geological Survey (2020). "Saltwater Intrusion". United States Geological Survey. Retrieved June 15, 2020.
  24. ↑ Lenntech (2020). "Sources of groundwater pollution". Lenntech. Retrieved June 13, 2020.
  25. ↑ 25.0 25.1 Rally for Rivers (2018). "How Trees Improve Groundwater Recharge". Rally for Rivers: India's Lifelines. Retrieved June 13, 2020.
  26. ↑ 26.0 26.1 Pfeiffer, Cynthia Lin, Lisa, C.-Y. (2014). "The Effects of Energy Prices on Agricultural Groundwater Extraction from the High Plains Aquifer". American Journal of Agricultural Economics. 96 – via JSTOR.
  27. ↑ 27.0 27.1 27.2 Morgan, Kelly (2017). "Smart irrigation: Agricultural water savings with improved irrigation scheduling". International Conference on AGRICULTURE & Horticulture. 10 – via LONGDOM.


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