Global Freshwater Scarcity

4/14/2015 , , , , , 0 Comments

The Amazon River in Brazil. Source: NASA

The Bloodstream of the Biosphere

Human pressure on the Earth’s Biosphere is so large that geologists have announced that we live in a new era, the Anthropocene, in which humanity is the largest driving force of global change. The mounting stresses on the biosphere to support 7,3 billion (to become 9 billion) people may cause collapses and major shifts in ecosystems, from local to global scales. The ability to generate social and economic well-being is now threatened. Freshwater is at the centre of this change.

Freshwater

Freshwater is the bloodstream of the terrestrial Biosphere. Greenwater (used by plants) and blue water (rivers and groundwater) are linked across all scales. It is a resource that supports human health, industry and energy generation. Many water systems have undergone ‘regime shifts’ whereby disturbances forces the water ecosystem to flip to an alternative stable state. For example, the Baltic Sea has gone from a low nutrient clear state to a high nutrient murky state due to eutrophication and overfishing. Potential future regime shift, with global implications, include the dieback of the Amazonian rainforest, Arctic ice loss and the Atlantic deep-water formation.

Water for food

Food production is the world’s largest user of freshwater. In many countries such as Brazil and China diets are changing to include more meat and dairy product which increases food water requirements. Globally, as much as 40% of the grain produced is converted to animal feed. By 2050, currently available water for croplands will not be sufficient for producing enough food for humanity. Agricultural water management is key to lowering freshwater depletion rates and increasing farm productivity. Global consumptive use of blue water has been estimated at 2600 km3 per year. Several regions already suffer from the widespread impacts of the overuse of blue water. River basins with withdrawals exceeding more than 40-60% of available water resources experience severe water scarcity. The number of people living in areas which suffer from blue water scarcity is soaring. In 2005, about 35% of the global population where living in areas with chronic water shortage.

Population living under water scarcity. Source: Rockström et al. (2014)

Unsustainable water use

About half of the river water withdrawn for societal use has evaporated, literally consumed during use, and about 25% of the rivers on land are highly affected by overuse of blue water. River depletion is considerable in irrigated regions of the world and many economically important river basins are already surpassing their ecological limits. Blue water security is subject to a high level of vulnerability to change in both Asia and Africa. For example, the Indus and Ganges-Brahmaputra-Meghna basins upon which some 1.5 billion people depend are highly vulnerable to change. Zones of particular concern are north-western India, the north China plain, the Great Plains of the US and the Central Valley in California. At the national scale, 5 countries are withdrawing more groundwater than can be recharged in aquifers, these include: Saudi Arabia, Libya, Egypt, Pakistan and Iran. 

Climate Change and rainwater

Until recently, humans have been able to assume that precipitation was relatively stable and predictable. However, new insights now show that this assumption no longer holds. Climate change is a major driving force of a changing water landscape and its projected that a 2 °C increase in average global temperatures will result in an increase of 40% of people living in absolute water scarcity. Floods and droughts will become more prominent and rainfall patterns could change. There are large uncertainties about future rain, monsoon and snow patterns that influence river flows. Glacial melt has been widely observed in the mountain water towers of the world, including the Himalayas, the Andes, the Alps and the Kilimanjaro.

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Wake up call for California?

4/09/2015 , , , , , 0 Comments

US Drought Monitor

Worst drought in a century

Last couple of years (2012-2014) California has experienced severe drought conditions. However, the worst effects won’t be felt until this year when the conditions continue due to lack of precipitation and record heat. This winter has been the warmest on record in California, resulting in less snow and rain. The overall trend toward drought persistence has continued, depleting already low snowpacks and reducing spring runoff for much of the region. The lack of snow raises concerns for this years spring and summer water supplies.

Griffin & Anchukaitis (2014)
California's record warm winter comes after the warmest year on record globally, 2014. The 2012-2014 Californian drought has already been claimed to be the worst drought in 1200 years, according to a new study. 

Last week governor Jerry Brown declared restrictions for water use for the first time in California history. Over 400 local water plants are now forced to reduce water consumption by 25% compared to 2013 levels. Other restrictions include: a ban on garden irrigation other than drip irrigation, limits on golf course and churchyard irrigation, detailed water use reporting by farmers etc. 

Previously, groundwater was only used as reserves but now they are pumping like crazy. Some regions have reported collapsing soil and salt intrusion, both a sign of overpumping. Despite the very serious water scarcity, California is the only state in Western US that have no limits on private pumping or consumption of groundwater. 

Farmers can buy water rights from one another and they can pump as much groundwater as they like. As a result, the state's groundwater has been depleted considerably. Gov. Brown recently signed a restricting groundwater use law but it will take years to implement and it doesn't require groundwater basins being run sustainably until 2040. Too little too late, in my opinion. 

Colorado river groundwater is also disappearing at a stunning rate. Streamflow from the river is the most overallocated in the world. Demand for this renewable resource is now outstripping supply, according to a 2014 study. Between December 2004 and November 2013, more than 75% of the water lost in the Colorado River Basin was from groundwater. The region has been experiencing drought conditions for the last ten years according NOAA.

Because of the long duration of these drought conditions, all kinds of people are becoming interested in expert opinion on climate-related topics. Unfortunately so far it seams like most are only interested in whom to blame. Hopefully Californians and the rest of Americans will start realising that climate change is already happening, and effecting them personally. Maybe then negotiations on climate change will take a turn for the better, but it has to happen before December 2015.

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Faster permafrost melt than previously thought

4/08/2015 , , , , , , 0 Comments

Cracked pattern in winter permafrost. Source: Brocken Inaglory (CC-BY SA 3.0)

Heat-producing microbes in Greenland permafrost soil

Permafrost is soil at or below the freezing point of water 0 °C that stays frozen for two or more years. Permafrost comprises 24% of the land surface in the Northern Hemisphere and can be found at Arctic ocean shelves and floor. It contains large quantities of trapped greenhouse gases such as methane and carbon dioxide, and is usually regarded as a carbon sink. Researchers have become increasingly worried that with climate change large permafrost areas could start to thaw and ultimately melt, releasing massive amounts of carbon that would exacerbate global warming. 

A small team of scientists working in Greenland have now found evidence that as microbes become active in permafrost, they produce heat, which can increase the rate of permafrost melt. In their paper published in Nature Climate Change, Hollesen et al. (2015) describes computer simulations that showed possible impacts of microbe activation in permafrost areas. Previous attempts at predictions for permafrost melt through modeling are now looking like they will have to be revised. 

Suspecting that microbes in the soil might have an impact on warming permafrost, Hollesen et al. collected 21 samples of permafrost soil from six locations across Greenland. They then exposed the samples to different temperatures in a laboratory. By monitoring the heat production from microbes they were able to gather enough information to create a computer simulation. That simulation revealed that as global temperatures rise, a feedback loop occurs in permafrost areas. Heat causes melting which stimulates the microbes that start decomposing organic material, and producing heat, which adds to the increased temperatures, on and on until the permafrost melts, releasing massive amounts of carbon into the atmosphere far earlier than previous models have predicted. 

One immediate consequence of thawing permafrost in Greenland is the potential for destruction of unexcavated archeological findings. The National Museums of Denmark and Greenland have now started several projects where decomposing wooden artifacts and bones from the first people on Greenland will help identify areas most threatened. This is mainly happening because the average temperature has risen by 2-3°C in Greenland. Thawing of protective permafrost leads to archaeological material rotting because the amount of oxygen rises and the decomposition process accelerate. Other concerns are related to coastal erosion, resettlement and infrastructure damage.
greenland artifacts.jpg
Archaeological sites in Greenland. Source: National Museum of Denmark
More long-term consequences of permafrost thaw is of course increasing greenhouse gas concentration in the atmosphere, and in turn a warmer climate. Previous estimates have pointed to 120 ± 85 Gigatonne of carbon emissions from thawing permafrost by 2100, which could increase global temperatures by 0.29 ± 0.21 °C. However, we now know that permafrost starts to thaw much earlier than expected, so we need to start including this knowledge into climate models or we risk overshooting the 2°C warming limit. For example, the most recent knowledge on permafrost/carbon feedbacks are not included into IPCC climate projections.

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