Rising above the low of peak water
Peak water is a new concept that indicates that the era of easy access to water is coming to an end. Professor Malin Falkenmark of the Stockholm International Water Institute believes it reveals that a rethink is needed
A new concept – peak water – has emerged. It indicates that the era of easy access to blue water is coming to an end in many regions of the world. Increasing water pollution, depleted river streamflow, overdrawn groundwater, water usability threatened by salinisation, and water for ecosystems sinking below the acceptable minimum, all point to a peaking of blue water resources. This theme is highlighted in The World’s Water 2008-2009 from the Pacific Institute. There is also a widespread green water scarcity linked to soil and land degradation but generally discussed as desertification.
Human ingenuity, coping strategies and fundamental rethinking on water management are urgently needed to mitigate the drivers of peak water – whether blue or green – and adapt to their effects on freshwater and other natural resources.
Borrowing momentum from the peak oil debate, the peak water concept has appeared in environmental texts, predicting that as future demand for water grows, its availability in many places will shrink. The term itself is a new and apt name for the present and looming threat of amplified water scarcity. At the 2008 World Economic Forum in Davos, Switzerland, water scarcity attracted considerable concern. A CEO Water Mandate was formulated with the aim to assess the level of water insecurity.
The International Water Management Institute (IWMI) has shown that a man-made blue-water scarcity, manifested in terms of river basin closure, is a problem developing mainly in irrigated regions, but covers more than 15% of all continental land. Blue water scarcity has conventionally been conceptualised by addressing use-to-availability ratio – also called criticality ratio. The usual recommendation is for water demand management to bring down over-appropriation. The relative amount that should remain unallocated to maintain aquatic ecosystem health has been specified as environmental flow. The water quality dimension of the unallocated flow is frequently neglected but poses a serious problem for both human and ecosystem health.
As population increases, a second dimension of blue-water scarcity has to be taken into account. The population pressure on the available water, or the level of water crowding, is a phenomenon referred to as chronic water shortage. When combined with high water stress, this results in severe water shortage. By combining these two dimensions it has been shown that 1.4 billion people are already living in over-appropriated areas.
An estimated 1.1 billion of these people live in areas that are also suffering under severe water shortage. In such areas, demand management will not be enough. These areas will require import to achieve food security.
For each aspect of water scarcity, the populations affected are expanding. Following predictable climate change, it can be foreseen that by 2050, depending on the rate of fertility decline, the population in countries with chronic water shortage will be 3-5.5B.
Looking at the other dimension of blue water scarcity, expressed as use to availability ratio, the population in countries with high water stress may rise to 4.5-7B people.
Green water may also be scarce in different ways. This leads to problems for food production, especially in semi-arid regions. Green water in the soil is exposing quantitative deficiency in vulnerable regions. Man-made green-water scarcity, which results in land degradation conventionally called desertification, is a phenomenon that has remained high on the political agenda since the 1970s. Natural green-water scarcity in semi-arid regions is caused by a lack of rain, which may, but may also not, increase with climate change.
Problems of green-water deficiencies caused by meteorological factors such as lack of rain can be met by irrigation in areas that do not also suffer blue-water shortages. In situations where the deficiency is man made and land degradation has left the root zone too dry to meet the water needs of crops, the deficiency can be mitigated by soil and water conservation. The way forward may be triple-green agriculture: green-water based, green for increased production, and green in the sense of being environmentally sound.
Globally, producing food for the growing world population will be challenging. By mid-century, half of the world population may live in countries where national food self-sufficiency is impossible.
Food trade will therefore be essential to eradicate hunger. If fertility declined following the UN medium projection, world food trade would still have to double by 2050. In low-income countries, cropland expansion will have to be accepted to make a decent level of food security possible. Food production ambitions might be lowered, for instance by avoiding unnecessary food losses from field to fork. Many countries will still remain import dependent.
Today’s water crisis is seen as a crisis of management, not of water shortage. Many international organisations mainly focus on blue water, and are more concerned with water stress caused by high use-to-availability ratios than with chronic blue-water shortages.
Tomorrow’s water-resources management will have to address green and blue water together with the strong link between land and water. This is especially critical in the semiarid tropics where poverty, under nutrition and population growth dominate. In Australia, a long sequence of drought years linked to climate change is causing both green and blue water shortages and revealing the needed shift towards a blue-green and land–water integrated approach. Humans are exerting multiple pressures on the freshwater resources.
Population growth, economic development, increasing water demands, increasing water pollution, increasing food expectations and climate change are squeezing from all fronts. Future-water resources governance must sharpen its tools to avoid approaching tipping points that would unbalance a peaceful world.
The global change debate is now raising concerns. At the recent Tällberg Forum in Sweden, the possibility of formulating planetary constraints for human activities was analysed.
As the water cycle is central in the operation of the global life-supporting system, determining a maximum blue-water withdrawal to safeguard a minimum river streamflow was one of the ten items under discussion. Water shortages are mounting while demand and consumption rapidly accelerate. The urgency of this situation cannot be overstated. Yet, the need to anticipate, prevent, mitigate and adapt to this reality and potential peak water remain either poorly understood or greatly underestimated.
Measures to control the massive driving forces behind global warming, population growth and economic development that rapidly accelerate unquenchable demand for water must be crafted. Water resources management will have to address the original resource – precipitation – to steer land and water-related human activities that are compatible at the basin level and strive towards hydro-solidarity.
Blue and green water explained
Blue water is the visible water contained in rivers and aquifers. Green water refers to the invisible water in the soil, which comprises a huge, but often forgotten, portion of water resources. Both sources originate from rainfall captured within the water divide of the catchment. Climate defines the constraints to human activities in terms of evaporative demand, droughts, dry spells, rainfall seasonality and variability. The roots catch the infiltrated rain, which supports plant production and vegetation covers in forests, grasslands and croplands, and which transpires back to the atmosphere. Runoff, resulting from the climate, topography, and the ability of the soils to absorb the rain, impact the consumptive water use of the vegetation.
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