Water: The Epic Struggle for Wealth, Power, and Civilization - Steven Solomon (2010)
Part I. Water in Ancient History
Chapter 1. The Indispensable Resource
Earth has aptly been called the “water planet.” It is, like ourselves, 70 percent water. Alone among the solar system’s apparently lifeless planets and moons, it contains abundant surface water in all three of its natural states—solid ice, gaseous vapor, and, most important, flowing liquid. Water’s pervasiveness and indispensable capability to transform and transport other substances played a paramount role in forging Earth’s identity as a planet and the history of all life upon it. Its deceptively simple molecular architecture of one oxygen and two hydrogen atoms possesses a mighty range of powers and functions unique among Earth’s substances. Water is the planet’s universal solvent: its extraordinary capacity to saturate, dissolve, and mingle with other molecules to catalyze essential chemical reactions makes it Earth’s most potent agent of change. It is water that conveys the life force of nutrients and minerals upward against gravity to crops, treetops, and the blood vessels of human beings. It is water that enabled the earliest forms of life to evolve and help create the planet’s oxygen-rich atmosphere. Water’s anomalous property of becoming less dense and more expansive as it freezes helps fracture rocks to promote geological change and fortuitously means that an insulating layer of ice forms first over the top of lakes and rivers, protecting the water-living creatures below.
Movements of liquid water and ice sheets over eons likewise carved many of Earth’s geographic landscapes and defined the changing characteristics of its habitats and climates. It is water’s exceptional capacity to absorb great amounts of heat before heating up itself that moderates seasonal surface temperatures and prevents the planet from becoming a perennially steamy hothouse like Venus or a frigid desert like Mars. It is the absence of water in the soil that causes deserts to suffer the extremes of heat in daytime and intense cold at night, while it is water’s presence that maintains comfortable ranges in temperate zones. Moving water creates and constantly redistributes the planet’s skin-thin layer of fertile topsoil, which when cultivated and magically watered in the right amounts yields civilized man’s daily bread—primarily wheat in the Mideast and Europe, rice in south Asia, maize and potatoes in the Americas, and tubers in Africa.
Among water’s most indispensable qualities is that it is Earth’s only self-renewing vital resource. Evaporated water precipitates in a desalinated and cleansed form over the planet through Earth’s continuous water cycle to restore natural ecosystems and make sustained human civilization possible. Although the remarkably constant total volume of accessible, self-renewing freshwater is infinitesimally tiny as a virtual few droplets of the planet’s total water, it has sufficed to provide all of the water needed to support mankind throughout the entirety of human history—until today.
Water appeared on Earth early in the planet’s infancy over 4 billion years ago, possibly through collisions with ice-bearing comets. Over time it assumed its familiar forms, such as oceans, ice sheets, lakes, rivers, streams, and wetlands on the surface, rainfall, snow, and water vapor in the air, and the invisible subsurface of shallow groundwater systems, soil moisture, and deep reservoirs of confined aquifers. Transmutations between water’s three natural states help drive Earth’s climate change cycles, prominently including the long fluctuations between cold, dry ice ages and warm, wet interludes like the present era.
Earth’s last great ice age lasted some 90,000 years and reached its zenith about 18,000 years ago with ice covering one-third of the planet, compared to about one-tenth today. With so much water locked up in ice, global sea levels were about 390 feet lower. Now separate landmasses were traversable on foot. As the ice sheets melted and receded over the next several thousand years, they enriched the soil, filled underground aquifers, and created the contours of our present geography of lakes, rivers, and harbor-rich coastlines and filled in the shallow seas and channels—the English Channel, for instance, land-bridged England and continental Europe as recently as 9,000 years ago. Thick forests grew in the new temperate zones left behind by the glaciers, particularly in the Northern Hemisphere, where the glaciers had been concentrated. Then, about 10,000 years ago, the planet entered an anomalous interlude in which the climate became both warm and unusually stable. It was under these highly favorable climatic conditions that human civilization made its debut on Earth’s stage.
Basic water conditions of aridity and moisture, seasonality and variable predictability patterns of precipitation, and river flow signatures and navigable lengths are defining elements of the planet’s diverse range of habitats to which each occupying civilization tried to gainfully adapt during its few moments in history. Heat dispersal by ocean currents and the blanket of warm atmospheric water vapor help keep Earth habitable for humans from the equator to the subarctic latitudes. Within these boundaries are a half dozen main landscapes, each with a unique hydrological identity: Near the poles is the bitterly cold, low-rainfall, high-permafrost, and poorly drained tundra. The taiga, featuring large coniferous forests, lay south of the tundra in the Northern Hemisphere. Temperate forests, with good soil, ample rainfall, and rich flora, follow next, moving toward the equator. Then comes a belt of semiarid grasslands with less-fertile soil and erratic rainfall, such as in the barely cultivatable prairie of the North American Great Plains, Africa’s savanna, and the steppes of central Asia. Interspersed among these regions are transition zones, notably one stretching from the Mediterranean to the Indus Valley and another in northern China, marked by drying, semiarid climates and several large rivers that flood over wide plains—the eventual cradle habitat of the ancient irrigation-farming-based civilizations. Between the 30-degree latitudes lie large deserts; around the equator are vast tropics with extreme rainfall, high temperatures, and rapid evaporation. Both are among the most water-fragile habitats on Earth—the former due to its dryness, and the latter due to its inundating, ever-soggy excess. Water also governs the crucial microclimates that exist within each basic zone. The seas play a dynamic role: it is the warm Atlantic Gulf Stream current that flows northeasterly from the Gulf of Mexico that keeps northern Europe wet and warm despite being at the same latitude as Canada’s frigid Hudson Bay, just as the swift, northeasterly Kuroshio, or Japan Current, in the Pacific Ocean warms North America’s coastal northwest. The Gulf Stream, in turn, also influences the prominent summer monsoons of Africa and Asia. Climatologists today postulate that the global conveyor belt circulation of deep and surface ocean currents acts as a key on-off switch of ice ages and is triggered by shifting mixtures of oceanic salinity and heat, particularly at the delicately balanced turnaround point in the North Atlantic. Similarly, the early signs of global warming are expected to express themselves in the form of more extreme precipitation events—more intense, frequent, and seasonally unpredictable storms, melts, and droughts. In short, every aspect of the past, present, and future of the planet and its inhabitants has been and will be powerfully influenced by water’s pervasive impact.
Despite Earth’s superabundance of total water, nature endowed to mankind a surprisingly minuscule amount of accessible fresh liquid water that is indispensable to planetary life and human civilization. Only 2.5 percent of Earth’s water is fresh. But two-thirds of that is locked away from man’s use in ice caps and glaciers. All but a few drops of the remaining one-third is also inaccessible, or prohibitively expensive to extract, because it lies in rocky, underground aquifers—in effect, isolated underground lakes—many a half mile or more deep inside Earth’s bowels. Such aquifers hold up to an estimated 100 times more liquid freshwater than exists on the surface. In all, less than three-tenths of 1 percent of total freshwater is in liquid form on the surface. The remainder is in permafrost and soil moisture, in the body of plants and animals, and in the air as vapor.
One of the most striking facts about the world’s freshwater is that the most widely accessed source by societies throughout history—rivers and streams—hold just six-thousandths of 1 percent of the total. Some societies have been built around the edges of lakes, which cumulatively hold some 40 times more than rivers. Yet lake water has been a far less useful direct resource to large civilizations because its accessible perimeters are so much smaller than riversides. Moreover, many are located in inhospitable frozen regions or mountain highlands, and three-fourths are concentrated in just three lake systems: Siberia’s remote, deep Lake Baikal, North America’s Great Lakes, and East Africa’s mountainous rift lakes, chiefly Tanganyika and Nyasa. Throughout history, societies have also widely accessed shallow, slowly flowing groundwater, which is the underground counterpart of surface rivers and lakes.
The minuscule, less than 1 percent total stock of accessible freshwater, however, is not the actual amount available to mankind since rivers, lakes, and shallow groundwater are constantly being replenished through Earth’s desalinating water cycle of evaporation and precipitation—at any given moment in time, four-hundredths of 1 percent of Earth’s water is in the process of being recycled through the atmosphere. Most of the evaporated water comes from the oceans and falls back into them as rain or snow. But a small, net positive amount of desalted, cleansed ocean water precipitates over land to renew its freshwater ecosystems before running off to the sea. Of that amount, civilizations since the dawn of history have had practical access only to a fraction, since two-thirds was rapidly lost in floods, evaporation, and directly in soil absorption, while a lot of the rest ran off in regions like the tropics or frozen lands too remote from large populations to be captured and utilized. Indeed, the dispersion of available freshwater on Earth is strikingly uneven. Globally, one-third of all streamflow occurs in Brazil, Russia, Canada, and the United States, with a combined one-tenth of the world’s population. Semiarid lands with one-third of world population, by contrast, get just 8 percent of renewable supply. Due to the extreme difficulty of managing such a heavy liquid—weighing 8.34 pounds per gallon, or over 20 percent more than oil—societies’ fates throughout history have rested heavily on their capacity to increase supply and command over their local water resources.
Some societies developed in landscapes that offered relatively abundant, easily accessible, water resources with reliable availability and moderate variations; others have been hindered by more water-fragile and arduous habitats marked by dearth or excess and, worst of all, frequent, unpredictable shocks like extreme droughts and floods that overwhelmed otherwise sound hydraulic planning. Each unique environment imposed opportunities and constraints that helped shape that society’s organizational patterns and history.
Adaptation is a constant necessity because water conditions are in flux. As historians Ariel and Will Durant have written, “Every day the sea encroaches somewhere upon the land, or the land upon the sea; cities disappear under the water…rivers swell and flood, or dry up, or change their course; valleys become deserts, and isthmuses become straits…Let rain become too rare and civilization disappears under sand… let it fall too furiously, and civilization will be choked with jungle.” Natural secular climate change alters conditions slowly, but dramatically, over time. As recently as 5,000 years ago the Sahara Desert was verdant grassland with hippopotamuses, elephants, and cattle herders, whose water has since evaporated and seeped away into deep, fossil aquifers, while today’s desiccating, windblown northern plain of the Yellow River was a watery swampland at the time it was a cradle of ancient Chinese civilization. Almost everywhere civilization has taken root, man-made deforestation, water diversion, and irrigation schemes have produced greater desiccation, soil erosion, and the ruination of Earth’s natural fertility to sustain plant life.
How societies respond to the challenges presented by the changing hydraulic conditions of its environment using the technological and organizational tools of its times is, quite simply, one of the central motive forces of history. Repeatedly, leading civilizations have been those that transcended their natural water obstacles to unlock and leverage the often hidden benefits of the planet’s most indispensable resource.