Fresh water is the ultimate renewable resource. And in large parts of the world it is the ultimate common resource too. The former is reason to be optimistic about future water security. After all, the world has an awful lot of the stuff. But most economists would raise a red flag of pessimism in respect of the latter. Fred Pearce, a British science writer and (ultimately) an optimist, does so too. The world would appear to be running out of water.
A problem with the renewable attribute of fresh water (97% of the planet's H2O is salinated and essentially poison) is that it doesn't necessarily get renewed in the right place or at the right time. Aquifiers (underground reservoirs, the largest sources of fresh water on Earth) do not get replenished by rain anything like as fast as they are mostly being emptied by human activity. Some wells today are sufficiently deep that they mine "fossil water" that will never be replaced, and in the meantime the porous rocks that previously retained groundwater suffer collapse and permanent capacity reduction. Many of the world's biggest rivers--part of the fast water cycle that brings it back into circulation a bit more quickly--are not where people can or want to live (inhospitable jungle or arctic tundra). Moreover the toxic stuff that natural processes (mainly evaporation) remove from untreated used water (salt, silt, sewage and industrial effluent) doesn't disappear but spoils the land it is often left on or the lakes it remains in.
Some activities use a lot more water than others. In the grand scheme of things, drinking, bathing and flushing toilets don't move the needle. Lawn sprinklers in developed deserts like Phoenix sound profligate perhaps. But growing rice, sugar, grains and livestock feed is far more water intensive. So is cotton. Yet much of the latter is grown in the most water-starved places on Earth. Pakistan--for example--is a major virtual water exporter via its cotton trade which relies on the flow from the Indus, and competes for it against other uses, including survival for some. This sounds both inefficient and ethically dubious. Israel's exports of fruit (a tiny part of its GDP) make for hydrological barminess given that the water needed to grow it is canalised from the Jordan, pumped from beneath its West Bank, or distilled out of the sea.
The commons attribute of water is largely inescapable, and its consequence is very visible at macro level--particularly in the case of large river basins that drain more than one country, which most of them do--and at micro level--with boreholes that plunder aquifiers ever deeper and drier.
In the macro case, persistent shortages and non co-operative abstraction by upstream states increasingly threaten water wars (the Six Day War in which Israel annexed Syria's Golan Heights--where the River Jordan rises--was allegedly one of these). In the micro case, Fred Pearce's global hydro-travelogue encounters numerous instances of tragic but rational over-extraction of unrefillable groundwater reserves, via the same logic that must have incentivised whoever cut down the last tree on Easter Island: "If I don't do it, someone else will, so I'm gonna".
Why has water demand increased so much to levels that cause Malthusian supply concerns? One reason is the agricultural green revolution, itself a cascade of innovations that solved the food equivalent of this issue two generations prior. Global food production doubled in thirty years thanks to that, but the water consumption required to achieve this outcome trebled; high-yield crops are productive with respect to land, but not at all with respect to water use, so as granaries filled, rivers emptied. A "blue revolution" to solve the resultant problem would be good at this point. There are straws in the wind, or drops in the ocean, that the author mentions.
The second reason is the predilection of governments to dam and divert rivers for irrigation (moving the water to the crops, rather than the reverse, and the crops are often the cash variety) and for production of hydroelectricity. The latter was long viewed as green energy by many, particularly in comparison to fossil fuel power, but the firm consensus today is that it isn't, particularly if the resulting drying basins fill with vegetation that decays releasing methane, which is a much more powerful greenhouse gas than the CO2 byproduct of burning carbon. Yet grand hydrological engineering projects are still popular, especially with more authoritarian regimes but not just with those. Dams and reservoirs have an alarming record of causing destructive floods amid prior promises of protecting against them--it is rather hard for them to be both water supply and sink simultaneously. And river beds reduced to a trickle poison the plains they used to irrigate naturally by depositing salt and silt that they previously carried away. The same happens with lakes and wetlands that dry up when their infall is diverted. Dessication, dust bowls and uninhabitable desert can be the result, with large scale irrigation often eventually creating bigger problems than it ever solved. The almost total destruction of the Aral Sea straddling Kazakhstan and Uzbekistan is one of the more striking examples of man made watergeddon in this regard.
Pearce holds out hope in his (2006) book for micro (bottom up) solutions rather than macro (top down) ones. Many of these are not innovations but traditional water management and "rain harvesting" methods of prior generations. Some such as drip irrigation are new, and point towards his hoped for blue revolution. Desalination is not likely to fly, or perhaps float, except in extreme situations (like Kuwait which already depends on it); it is too expensive.
Some reversal of big fixes is evident too, such as giving rivers more space by restoring flood areas. This is in recognition that rapid-drainage remedies for flood risk merely expose the weakest link (which overflowing water finds astonishingly quickly), and that they are also profoundly illogical in places like Los Angeles, a water starved desert city 70% encased in non-porous concrete, which is at simultaneous risk of both drought and floods.
Not a polemic by any measure, but a wonderfully informative education via many stories, this book is a fantastic window into apparent hydrological illogic, and sense. Should have read it years ago.
A problem with the renewable attribute of fresh water (97% of the planet's H2O is salinated and essentially poison) is that it doesn't necessarily get renewed in the right place or at the right time. Aquifiers (underground reservoirs, the largest sources of fresh water on Earth) do not get replenished by rain anything like as fast as they are mostly being emptied by human activity. Some wells today are sufficiently deep that they mine "fossil water" that will never be replaced, and in the meantime the porous rocks that previously retained groundwater suffer collapse and permanent capacity reduction. Many of the world's biggest rivers--part of the fast water cycle that brings it back into circulation a bit more quickly--are not where people can or want to live (inhospitable jungle or arctic tundra). Moreover the toxic stuff that natural processes (mainly evaporation) remove from untreated used water (salt, silt, sewage and industrial effluent) doesn't disappear but spoils the land it is often left on or the lakes it remains in.
Some activities use a lot more water than others. In the grand scheme of things, drinking, bathing and flushing toilets don't move the needle. Lawn sprinklers in developed deserts like Phoenix sound profligate perhaps. But growing rice, sugar, grains and livestock feed is far more water intensive. So is cotton. Yet much of the latter is grown in the most water-starved places on Earth. Pakistan--for example--is a major virtual water exporter via its cotton trade which relies on the flow from the Indus, and competes for it against other uses, including survival for some. This sounds both inefficient and ethically dubious. Israel's exports of fruit (a tiny part of its GDP) make for hydrological barminess given that the water needed to grow it is canalised from the Jordan, pumped from beneath its West Bank, or distilled out of the sea.
The commons attribute of water is largely inescapable, and its consequence is very visible at macro level--particularly in the case of large river basins that drain more than one country, which most of them do--and at micro level--with boreholes that plunder aquifiers ever deeper and drier.
In the macro case, persistent shortages and non co-operative abstraction by upstream states increasingly threaten water wars (the Six Day War in which Israel annexed Syria's Golan Heights--where the River Jordan rises--was allegedly one of these). In the micro case, Fred Pearce's global hydro-travelogue encounters numerous instances of tragic but rational over-extraction of unrefillable groundwater reserves, via the same logic that must have incentivised whoever cut down the last tree on Easter Island: "If I don't do it, someone else will, so I'm gonna".
Why has water demand increased so much to levels that cause Malthusian supply concerns? One reason is the agricultural green revolution, itself a cascade of innovations that solved the food equivalent of this issue two generations prior. Global food production doubled in thirty years thanks to that, but the water consumption required to achieve this outcome trebled; high-yield crops are productive with respect to land, but not at all with respect to water use, so as granaries filled, rivers emptied. A "blue revolution" to solve the resultant problem would be good at this point. There are straws in the wind, or drops in the ocean, that the author mentions.
The second reason is the predilection of governments to dam and divert rivers for irrigation (moving the water to the crops, rather than the reverse, and the crops are often the cash variety) and for production of hydroelectricity. The latter was long viewed as green energy by many, particularly in comparison to fossil fuel power, but the firm consensus today is that it isn't, particularly if the resulting drying basins fill with vegetation that decays releasing methane, which is a much more powerful greenhouse gas than the CO2 byproduct of burning carbon. Yet grand hydrological engineering projects are still popular, especially with more authoritarian regimes but not just with those. Dams and reservoirs have an alarming record of causing destructive floods amid prior promises of protecting against them--it is rather hard for them to be both water supply and sink simultaneously. And river beds reduced to a trickle poison the plains they used to irrigate naturally by depositing salt and silt that they previously carried away. The same happens with lakes and wetlands that dry up when their infall is diverted. Dessication, dust bowls and uninhabitable desert can be the result, with large scale irrigation often eventually creating bigger problems than it ever solved. The almost total destruction of the Aral Sea straddling Kazakhstan and Uzbekistan is one of the more striking examples of man made watergeddon in this regard.
Pearce holds out hope in his (2006) book for micro (bottom up) solutions rather than macro (top down) ones. Many of these are not innovations but traditional water management and "rain harvesting" methods of prior generations. Some such as drip irrigation are new, and point towards his hoped for blue revolution. Desalination is not likely to fly, or perhaps float, except in extreme situations (like Kuwait which already depends on it); it is too expensive.
Some reversal of big fixes is evident too, such as giving rivers more space by restoring flood areas. This is in recognition that rapid-drainage remedies for flood risk merely expose the weakest link (which overflowing water finds astonishingly quickly), and that they are also profoundly illogical in places like Los Angeles, a water starved desert city 70% encased in non-porous concrete, which is at simultaneous risk of both drought and floods.
Not a polemic by any measure, but a wonderfully informative education via many stories, this book is a fantastic window into apparent hydrological illogic, and sense. Should have read it years ago.
via International Skeptics Forum http://ift.tt/2atJCV9
Aucun commentaire:
Enregistrer un commentaire