https://theconversation.com/how-ancient-water-management-techniques-may-help-prairie-farmers-experiencing-drought-168920
[images in online article]
This year witnessed one of the hottest and driest summers in recent
history for Western Canada and the American Southwest. The resulting
droughts adversely affected food supply and helped send meat prices
rising three times faster than inflation.
Despite the severity of these droughts, the worst may be yet to come.
Extreme weather events are expected to become increasingly severe and
frequent in the Prairies, with longer dry periods coupled with the risk
of floods from intense rainstorms.
While Canada benefits from a world-class agricultural technology
industry, lessons can also be drawn from low-tech solutions developed by
ancient societies that flourished in arid climates. One such society was
the Nabataean culture, which thrived in the hyper-arid deserts of
Jordan, northern Saudi Arabia and southern Israel 2,000 years ago. For
over a decade, I have worked on Nabataean and Roman archeological sites
of this region, exploring their building practices and innovative
strategies for overcoming environmental limitations.
Masters of hydraulic engineering
Known for their rock-carved monumental facades at the UNESCO World
Heritage sites of Petra (their capital) and Hegra, the Nabataeans grew
rich from trading incense between southern Arabia and the Mediterranean.
But it was another skill that allowed them to flourish in their arid
homeland.
Drawing on local techniques as well as those adopted from neighbouring
cultures, the Nabataeans became masters of hydraulic engineering. They
constructed complex water management systems that included dams,
catchment systems, underground cisterns and aqueducts. These systems
were designed to maximize the amount of rainwater collected and stored
during the wet winter months and to minimize the amount of water lost
through evaporation during the dry summer months.
At Petra, the Nabataeans constructed a network of dams to protect their
capital from flash floods and covered channels to deliver water to the
city centre. In the surrounding hillsides, they built terraces to absorb
runoff, mitigating flood risk and supporting agriculture. So effective
were these catchment and delivery systems that the Nabataeans built
open-air pools and monumental fountains in Petra as ostentatious
displays of their wealth and power.
South of Petra, at the archeological site of Hawara (modern Humayma),
Canadian archeologists have explored and documented the settlement’s
extensive water supply system. Here, catchment systems directed
rainwater runoff to large cisterns that stored it for use in the dry
season. These cisterns were roofed to prevent evaporation and were
furnished with settling basins to collect sediment. A 26.5-kilometre
spring-fed aqueduct also supplied this settlement with drinking water.
Much of this system is still in use today.
Ancient techniques for a modern problem
Despite being developed and constructed two millennia ago, efforts are
currently underway to revitalize the Nabataean water management systems
around Petra to help with flood control and support agricultural
development. Elsewhere across the globe, archeology has advanced our
understanding of sustainable farming and holds the potential to
contribute meaningfully to contemporary water politics. While
implementation of these historical solutions may not by themselves solve
the complex issues we currently face, they will likely play an important
role in helping us adapt to a warmer and dryer climate.
Although the climate and hydrology of the Canadian Prairies are very
different from the deserts of northern Arabia, some similarities exist.
Just as winter rains in northern Arabia sustained life during the summer
months, runoff from snow melt in the Prairies plays an important role in
recharging groundwater and represents a significant portion of stream
flow during the spring.
Like the underground cisterns built by the Nabataeans, excavated
depressions known as dugouts are an important source of water for
Prairie farmers. While these human-made reservoirs can be supplied by
groundwater, they often rely on spring snow melt. During the drought
conditions of this past summer, however, many of these dugouts dried up,
forcing many farmers to rely on pumped groundwater, which comes with its
own set of issues.
Adopting sustainable practices similar to those used by the Nabataeans
to maximize the amount of water collected and minimize the amount lost
to evaporation can help increase the effectiveness of these reservoirs.
Just as the Nabataeans placed their cisterns to maximize the catchment
of runoff, dugouts should be strategically located in fields to collect
as much snow melt as possible. The amount of snow melt captured can be
further increased by the use of well-designed shelterbelts, which
comprise rows of trees and shrubs that act as a windbreak and can also
encourage the accumulation of snow.
Settling tanks such as the ones the Nabataeans built to prevent the
accumulation of sediment in their cisterns, could also be used to
prevent sedimentation in dugouts, improving both storage capacity and
water quality.
The Nabataeans were also careful to avoid evaporation, and modern
dugouts may benefit from being covered to minimize water loss. Global
studies have shown the effectiveness of physical covers at slowing the
rate of evaporation, and recently California proposed covering its
canals with solar panels to help conserve its water supply while also
producing green electricity.
Part of an integrated strategy
While greater investment in water storage systems will improve water
security in the Prairies and mitigate the affects of prolonged droughts,
these storage systems may also have the added benefit of reducing flood
risk by retaining runoff.
Although the adoption of these low-tech and sustainable solutions will
not by themselves drought-proof the Prairies, when combined with
innovative cropping techniques they may play an important role in
helping Canada’s farmers mitigate the growing impacts of climate change.
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