August 11, 2013
Peak Water…Are we running out of Groundwater?
Peak Oil has generated headlines since American geologist M King-Hubbert first developed the concept in 1956. In recent years, spurred on by fears of carbon-induced climate change and dwindling oil-resources, we have begun to develop alternatives to oil. However, in an article, Lester Brown of the Earth Resources Institute argues that the real threat to our future is Peak Water. There are substitutes for oil, but not for water. We can produce food without oil, but not without water.
We drink around 4 litres of water per person per day whereas the food we eat requires around 2000 litres per day (for irrigation, meat production and food-processing). Around 40% of the worlds food is produced with irrigation.
Groundwater is pumped to irrigate crops and as the world’s population and living standards have increased, so too pumping has increased to meet increasing demand. In some cases, the groundwater being pumped is “fossil” water – water that was recharged many thousands of years ago that is not currently replenished. In other cases, the rate of pumping simply exceeds rates of replenishment. In either event, groundwater levels fall, well yields start to decline and land often subsides with associated structural damage to infrastructure. Less water for irrigation means declining food production.
NASA launched the GRACE satellites in 2002. The GRACE program measures changes in the Earth’s gravity field. Interpretation of GRACE data confirms large volumes of groundwater depletion in many areas of the world. The situation is particularly acute in the Middle East, northern India, northern China and the central and southwestern United States. These are some of the areas Lester Brown identifies as areas where grain yields have already started to fall.
The decline in groundwater resources also affects ecosystem functions i.e. the environment starts to degrade beyond that which is acceptable. The examples are many:
- The flow in rivers that is supported by groundwater baseflow may start to decline to the point that aquatic health is affected (for example the Platte River that drains from the High Plains Aquifer in the US eg. Lewis and Saunders 2001).
- Saltwater from the sea may intrude coastal aquifers to replace depleted fresh groundwater resources affecting the quality of coastal rivers, vegetation and agriculture over large areas (for example the coastal aquifers along the North African coast in Tunisia and Libya e.g. Gaaloul et al 2012).
- Wetlands may shrink or disappear with the associated loss of unique habitats and fisheries (for example over 50% of the world’s wetlands have been lost in the past 100 years, Australian Geographic 2012)
However, there are some key differences that challenge the analogy between Peak Oil and Peak Water. Principally these revolve around the value of water. Water is effectively unlimited if we spend enough – i.e. we could desalinate large volumes of seawater – the value of water simply does not justify this now. However, as scarcity drives the value higher, so the price that can be paid for water supply should increase – making more water available. The low value of water also means it is geographically bound –there is not a global economy for water. Thus, the concept of Peak Water needs to be considered on a regional scale.
Many uses of water are not consumptive. For example, water that is lost to evaporation from an irrigation system may ultimately return to the water system as precipitation. However, this may not occur in the same location and may take a long time. The use of abstracted water is not always efficient and some may ultimately report to waste streams as effluent from irrigation, industry and mining/oil and gas operations. It has been estimated that over 10% of global sea level rise can be attributed to the discharge of excess groundwater into the ocean (e.g. Konikow 2011) and this contribution continues at between 0.4mm/yr and 0.8mm/yr (by comparison sea level rise is currently occurring at around 3mm/yr).
So what does all of this mean? Peak Water may not be as clearly defined as Peak Oil and it will likely vary in time and space. Notwithstanding, clearly we should aim to use our water resources as efficiently and sustainably as possible. However, Dr Peter Gleick of the Pacific Institute, in its 7th periodic review of the state of the world’s water resources, notes there is no easy technical solution or “Hard Path”. Rather the shift should be towards a “Soft Path” that encompasses a range of measures:
- Prioritizing the needs of drinking water and environmental water requirements to maintain a minimum level of environmental function.
- Match water quality with beneficial use – use brackish water where the user can tolerate brackish water and reserve freshwater for uses that require fresh water.
- Efficiency – for example the re-use of grey water and the managed recharge of surplus water (for example urban runoff, industrial or mine dewatering surpluses and so forth).
- Development of water markets that encourage investment in the above measures through the assignment of a value to water; and finally
- Often, water management is the result of local practices at a community level and community engagement is a key element of sustainable water resources management.
The National Water Initiative implemented in Australia in 2004 essentially aims to implement these “soft path” measures. It is the NWI that drives much of the approach to licensing and the water-aspects of environmental approvals in Australia. For the mining and unconventional gas industries in Australia, the determination of groundwater-dependent ecosystems, environmental water requirements and the sustainable management of surplus “produced” water are critical components of the approval and on-going regulatory and social licenses to operate. AQ2 can help address many of these objectives.
Australian Geographic, October 2012, “Half the Worlds Wetlands Destroyed in 100 years”, Online article, http://www.australiangeographic.com.au/journal/half-of-worlds-wetlands-destroyed-in-100-years.htm
Gaaloul N, Pliakis F, Kallioras A, Schuth C, Marinos P (2012), “Simulation of Seawater Intrusion in Coastal Aquifers: Forty Five Years Exploitation in an Eastern Coast Aquifer in North East Tunisia”, The Open Hydrology Journal, 6 (supplement 1-M6), pp 31-44.
Konikow LF 2011, “Contribution of global groundwater depletion since 1900 to sea-level rise” , Geophysical Research Letters 38(17).
Lewis ASWM and Saunders JF (2001), “Analysis of groundwater exchange for a large plains river, Colarado, US”, Hydrol Processes 15 pp 609-620.
National Geographic, May 2012, ”Groundwater depletion accelerates sea level rise”, Online article, http://news.nationalgeographic.com.au/news/2012/05/120531-groundwater-depletion-may-accelerate-sea-level-rise/
Pacific Institute 2011, “The Worlds Water Vol 7”, Island Press, US.