That water is critical to all life on our planet, humans included, is well understood by all. Much less appreciated is water’s influence on the wide range of natural cycles on Earth from energy to weather to climate. In fact, water – it’s movement, forms, availability, and transportability – has directly shaped and continues to define the future of this planet and all of its inhabitants.
We believe our planet Earth to be at least 4.3 billion years old. That’s the reading that showed up on the Sensitive High Resolution Ion Microbe Probe or SHRIMP, based on the decay rate of uranium in a Western Australian rock discovered in 1982. The oldest marine fossil was dated a half a billion years later, 3.85 billion years old, in a Greenland stone. The life form detected was not a visible fossil but rather simply a chemical residue detecting that life was once present. Victoria Bennett, its discoverer, said “we can only guess what the organism might have looked like. It was probably about as basic as life can get, but it was life nonetheless. It lived. It propagated.” And it appeared just as the Earth was cooling enough to develop a solid external crust.
Scientists believe that conditions at the time were highly unsuitable for life as we know it, little oxygen, abundant hydrochloric and sulfuric acid in the atmosphere, and little sunlight. Yet as Dr. Bennett stated “ …there must have been something that suited life. Otherwise we wouldn’t be here.” Classic experiments in 1953, tried to mimic that ancient primordial mix. A flask of water mixed with a flask of methane, ammonia and hydrogen sulfide gasses, and an electric spark thrown in, delivered a thick green soup within a few days. Analysis revealed amino acids, fatty acids, and sugars. Suddenly we could imagine an ancient world and our own beginning. Some fifty years later, theories have been refined. First we believe the atmosphere was more hostile to life, a blend of nitrogen and carbon dioxide less inclined to react to energy. Second, rerunning the experiment under these conditions yielded more primitive, simple amino acids. Still, as Dr. Bennett suggested, something suited life back then.
We know today that all life is built primarily around four elements, two of which are included in water. They are carbon, hydrogen, oxygen and nitrogen. Lesser amounts of sulfur, phosphorous, calcium and iron complete the palate and allow creation of three dozen plus combinations from which you can build anything that lives. And regardless of which of the many scenarios of life’s beginnings you wish to embrace, water is a central feature to all.
If life began 3.8 billion years ago, little occurred over the next two billion years. During this time, it is felt that bacteria dominated and thrived. Very early in this period the primitive blue-green algae mastered hydrogen extraction from the water bodies, and in the process released oxygen into the atmosphere. Scientists Lynn Margulies and Dorian Sagona termed it “undoubtedly the most important single metabolic innovation in the history of life on the plant.” Why? Because, over the first 2 billion years of Earth’s life, these blue-green algae, ran a photo- synthesis factory that bumped up oxygen levels in our atmosphere to modern concentrations. And with that, the air and oceans, lakes and rivers changed, and a new type of complex cell, with a nucleus, and organelles, multiple protective membranes, the capacity to replicate and the ability to build proteins appeared.
Life evolved and here we are. The planet Earth, its waters and its oxygen rich atmosphere, have supported our many diverse life forms most of which thrive because their chemistry is advantaged in an oxygen and water rich world. We have sprung from and are dependent upon each other. The bacterium today is 75% water and, depending on type, either must have or must be shielded from oxygen to survive. We on the other hand, have an absolute requirement for oxygen and are 65% water. What we ingest to sustain ourselves, whether steak (74% water when alive) or tomato (90% water), also require water and engage in the oxygen cycle.
Water is built through the loose bonding of water molecules. Each molecule consists of one relatively large oxygen atom connected to two smaller hydrogen atoms (H20). The three atoms connection to each other is strong and resists separation. In contrast, the connection of one H20 to another is relatively weak, with molecules pairing and unpairing billions of times a second. If one were to look at a body of water, only 15% of the H20 molecules would be “touching” each other at any one time. This allows water to be parted easily by a boat, or a swimmer or a diver. That said, the rapidity and number of recurring bonds create enough “solidity” to allow water drops to form, surface tension to exist, water bugs to walk, and skipping rocks to skip on water.
Water has no taste or smell. It is formless and transparent. It can freeze and scald. Most of the water on earth is saltwater existing in the oceans. Some 3.8 billion years ago our oceans reached their current volume, capturing and containing 97% of the planets water in salt form. The Pacific Ocean contains 53% of this salt water, the Atlantic Ocean 24% and the Indian Ocean 21%. This leaves a little over 3% of the salt water for all the other oceans on earth. The Pacific Ocean itself is massive, covering ½ the planet, a surface area larger than all of our land masses combined. (Table 1.1)
The average ocean depth is 2.4 miles with the deepest point some 7 miles below the surface at Mariana Trench in the Western Pacific, 250 miles from Guam. As for the water itself, it only contains about 2 teaspoons of common table salt per liter, but much larger amounts of other minerals and salts that make ingestion of it by humans deadly. This is largely due to the ability of ingested salts to draw water rapidly out of our cells and trigger rapid dehydration and organ failure. That said, in certain parts of the body, we demonstrate strong affinity with the sea, creating sweat droplets and producing water tears that are remarkably similar in composition to seawater. Yet if we humans dare ingest seawater directly, we seal our own fates, for the size of the total salt load in ocean water is not small. In fact, our oceans contain a mass of salts large enough to bury all land to a depth of 500 feet. But, other species seem to do quite well in seawater. In fact some estimates suggest our seas support over 30 million species spread unevenly with sites like coral reefs – rich in warmth, light, and organic matter – occupying only 1% of the ocean surface but supporting 25% of the ocean’s fish population.
The understanding that our land, its surface waters, and we human inhabitants can positively or negatively impact the future of our oceans, is a relatively new insight. Back in 1890, when T.H Huxley headed a British Royal Commission examining the collapse of the herring industry, he openly ridiculed those who suggested that humans were adversely impacting the marine environment. At the time, we had a very poor understanding of the nature and volume of pollutants, of runoff, and territorial contributions to our oceans.
Through the years, oceans have carried a mystique of deep, dark, unexplored, impenetrable, and therefore some how safe from us. How is it possible that anything that large could be harmed? But increasingly we are viewing our ocean waters in a scientific, rather than a mythological context. We know that seawater is 80 times as dense as air, which allows it to support tremendous biomass at low expenditures of energy. We know this medium is a comprehensive life support system. It transports, provides food, and allows for reproduction. Seawater is biologically bred for life. It is a great buffer and a good solvent. It manages temperature well. A 20 degree shift in air temperature alters surface sea temperature by only a degree.
Though ocean waters are large, they do move. They acquire particulates, good and bad, from surface land runoff and vertical upwelling from the ocean floor. In a single month, an object will travel 700 miles. The path the object will take is effected by tidal currents, weather and atmosphere and ocean geology. Life in the ocean is columniated. The upper surface is highly productive with access to sunlight. Species feed on phytoplankton and on each other. They transport, nourish, support eggs and larval, and generally propagate. Some migrate extensively like tuna, while others are stationary like coral. Each species chooses or is chosen by a habitat. The habitat provides unique life conditions, shelter and protection. Surface conditions may vary widely, but these species are shielded compared to their terrestrial cousins. The ocean flow systems are distinctly 3 dimensional, while the land based river and lake catchment systems are more 2 dimensional, with a relentless one way flow to the oceans. Water may be trapped along the way due to soil or sediment buildup, flooding beyond catchment boundaries, blockages in mountain ranges, or human flow diversion.
We think we know the sea, but most of its life forms – abundant and microscopic – are invisible to us. The sea carries mystery, as fish and invertebrates move in and out of territories. Part of that mystery is the myth that the supply of life is endless, non-consumable, and inexhaustible. In the latter half of the 20th century, this has been generally been recognized as illogical and self-destructive. We now know that our capacity and technologically aided skills at catching fish exceed the fish communities reproductive capacity. We know that actions in fresh water catchbasins can undermine the health of coastal ecologic systems. And we appreciate that healthy oceans are a common good. Governance on the oceans is fundamentally different from territorial oversight. Oceans all collectively owned, must be stewarded to survive and thrive, and require guiding principles, laws and regulations which in turn require enforcement.
If the amount of water stored in oceans is remarkably large, the amount contained in the atmosphere is comparably small. In fact, only .001% of Earth’s water supply exists in the clouds. Most of these millions of gallons evaporate from our oceans returning to land or sea in an average 12 days. The time above does not however match the time below. A water molecule in the sea on average will remain as part of the sea for some 100 years. If part of a lake, the tour is somewhat less, an estimated 10 years. If landing in fertile soil, a water molecule can plan to be absorbed by a plant and re-released to the atmosphere in hours or days. But without the aid of plants, should the molecule join others as part of the ground water, there it will be for many years. If oceans deliver water, they also deliver oxygen into the atmosphere. Algae and microbes in the ocean water produce and release around 150 billion kilograms of oxygen per year.
Three quarters of the fresh water existing on earth exists as ice, and is largely unavailable to humans. The South Pole alone contains some 6 million cubic miles of ice. Here the ice is 2 miles deep, compared to only 15 feet of ice on the North Pole. And were it all to melt, the world’s oceans would rise 200 feet. By comparison, were all the atmospheric moisture to fall at once as rain, we would gain 1 inch at most. For all the ice we have, we used to have more. 25,000 years ago, 30% of our land was covered by ice. Today, 10% of the land has ice cover and 14% permafrost cover.
The fresh water then, largely evaporating from ocean seawater, is constantly on the move, condensing, freezing and thawing; moving up and down, side to side, in and out. On the land it travels on the surface or below the surface at widely different speeds, forming streams, rivers with river basins, and eventually draining into the seas. Along the route, some penetrates the earth to recharge underlying aquifers or water reservoirs hidden below the earths’ crusts. Others will be drawn out at river basins to enrich soils and support agriculture, or cool turbines at manufacturing sites. At the end of the day the ground water and surface water, less that 1% of all the water on Earth, represents our potentially accessible fresh water supply. And on this fragile system, the blossom of human life survives.
It is understandable then that humankind has taken care not to wander far from our water sources. In fact civilization has carefully settled largely next to seas and river basins, supplemented these with man-made canals, and has grown in numbers as a result. The water today not only sustains life but also generates food, energy and products. What happens at the river level often magnifies what is happening on the atmospheric level. For example, the regional drought that gripped Africa during the 1970’s and 1980’s was marked by decreased precipitation levels of 25% but reduced annual river flows in the region by 50%. Or approaching it from the other direction, in areas where sea levels rise, brackish water (a combination of sea and fresh water) moves further and further inland, significantly effecting the lives and livelihood of humans in these river basins.
The hydrological cycle itself, throughout human history, has been dynamic. It is now generally accepted that the assessments of the Intergovernmental Panel on Climate Change have accurately identified that global temperatures will rise 1.4oC to 5.8oC between 1990 and 2100 largely as a result of the emission of greenhouse gases especially carbon dioxide (CO2). In response, ocean levels will rise, more energy will exist in the climate system, and the global hydrological cycle will intensify. How will this be expressed? We’ll see changes in amount and intensity of precipitation, in seasonal distribution, and in frequency. These events in turn will lead to changes in magnitude and timing of water runoff, intensity of floods and droughts, regional water supply levels, levels of surface and ground water. In short, “terrestrial components of the hydrological cycle amplify climate input.” Translation, when it comes to water, weather matters.
Precipitation across the globe is highly variable from highs of 2400 millimeters per year in the tropics to lows of 200 millimeters or less in the subtropics. Near the poles and at high elevations, the precipitation falls as snow, some 17,000,000,000,000 tons worldwide per year. Extremes in precipitation mean floods on the one hand and droughts on the other. Rates of evaporation are largely driven by availability of surface water exposed to air. Rates are at approximately 2000 millimeters per year in the subtropics decreasing to about 500 millimeters per year as you approach the poles.
Soil is a significant reservoir for water. Amounts are not only driven by the rates of precipitation and evaporation but also by soil type and depth, vegetation, topography, and seasonality. Within a small area, levels of water absorption and soil moisture are highly variable. The top two meters contain the majority of the moisture, estimated at 16,500 cubic kilometers. Significant water also collects in subterranean spaces. The presence of stored ground water is often revealed by surface springs. The supply of fresh water throughout human existence has greatly exceeded our ability to access it. That said, ground water has been critical to human development and in the past 50 years, with advances in drilling and pump technology, groundwater has rapidly become the worlds “most extracted raw material”. Whether city (70% of the piped water supply of the European Union) or rural (sub-Saharan Africa), manufacturing or agriculture (Asia’s green agriculture revolution), groundwater is a major driver in human development as we enter the 21st century.
The challenge remains how best to scientifically manage this raw material to assure long term sustained development. This requires a better understanding of how the ground water systems function, their recharge processes and their relationships to surface water bodies. It also means managing and protecting the purity and integrity of the resource, a knowledge of the geology, better monitoring of groundwater levels, and real-time data of depth, flows, and extraction levels. But for the effort, the rewards are high. Groundwater is the predominant strategic reservoir on Earth, some 30% of the global fresh water total and 98% of the drinkable and potential accessible supply. And compared to surface water, there is very little loss to direct evaporation.
While humankind can greatly benefit from wise management of ground water sources, they can equally place itself at great risk by mismanagement of this resource. From 1950 to 1970, the developed world invested heavily in groundwater exploration. Over the following two decades the developing world weighed in as well. Today, groundwater provides 50% of the worlds’ drinkable water, 40% of that used by industry, and 20% of that used for agricultural irrigation. Its economic benefits include local availability, drought resistance, and good quality. Approximately 1.2 billion urban citizens worldwide subsist on well, borehole or spring water. In countries like India, every sector is reliant. 80% of rural domestic supply and 70% of India’s agriculture output is the result of groundwater extraction. In some areas such as the North China Plain and among some 100 Mexican aquifers, extraction rates of 5 to 10 km3/year are clearly not sustainable. In such areas, urban needs already complete with those of agriculture, and lack of waste water management and careful integrated planning further complicates the modern picture.
As water seeps into groundwater aquifers it also seeps out through watercourses, wetlands and coastal zones. Recharge rates are highly variable and affected by changes in surface vegetation, surface water diversion, changing water table levels, and climate cycles. Sustainability issues include inefficient use, social inequity, unsustainable extraction, icy weather reductions, aquifer damage, land compaction, and ecosystem damage. All of the above are under human control. Aquifers are far more resistant to contamination than are surface water bodies. But once contaminated, aquifer damage is difficult to reverse.
As with most enlightened policy, good planning and prevention pays off. Sound system design, proper land use rights, ongoing investment in technology, stakeholder participation, and careful monitoring, design and operation are critical. But what’s unique about water is that water flows. And in flowing, it crosses multiple jurisdictional borders. So proper management and planning require intergovernmental cooperation. This holds true to some extent for surface water supplies as well. River basin networks cover 45% of the earth’s land and nourish locations that support 60% of our global population. There are over 15 million lakes and reservoirs on the planet, though the 145 largest hold 168,000 km3 of water or 95% of the total lake water on Earth. Of this, approximately half is fresh (91,000km3) and half is salt-water (850,400km3). The Caspian Sea, one of the world’s largest lakes, contains 91% of the Earth’s inland salt water. (Table 1.2)
Where there are lakes, there are dams. These are built for flood control, to support irrigation, to replace over consumption of ground water, and to support recreation among other things. As of 2000, there were 47,655 large dams (a height of more that 15 meters) and more than 800,000 smaller ones. Dams have been around for at least 5000 years. In 2004, some 300 dams over 60 meters in height were under construction. More are expected in the future to meet demand. In addition there are 633 large reservoirs with a total volume of 5000 km3 (63% of the total reservoirs storage volume) which capture approximately 40% of the earth’s fresh run-off water and 30% of river sediment. The reservoirs not only capture surface water but also increase surface area evaporation of some 200 km3 of water per year. (Table 1.3)
By comparison river volume of surface water is quite small, but highly strategic. In many parts of the world, river water is the most accessible and certainly most overutilized and stressed fresh water resource. While most rivers reach the ocean, some do not, including those draining into the Caspian Sea (a lake), the Arabian peninsula, central Australia, North Africa, and Middle and Central Asia. These feed 20% of the Earth’s land surface but contain only 2% of its fresh water run-off. In contrast, the Amazon River in Latin America, the world’s longest river captures 16% of the world’s runoff; and the Amazon, Ganges (India), Congo (Central Africa) Yangtze (China) and Orinoco (Venezuela) together capture and transport 27% of the runoff, all to the sea. The average total flow per year from land to sea for all rivers was 42,800 km3. This runoff occurs mainly (60 – 70%) in spring and early summer. Most flooding occurs during this time and carries large amounts of sediment and organic material with it. While large year to year variations in flow occur, careful studies over 65 years show no significant trends.
Before extensive human interventions, surface water quality varied as a result of land use, geology climate, biologic activities, and geography. But today there are few examples of natural surface water bodies. The impact of industry, agriculture, wastewater mismanagement and urbanization have affected the chemical composition of average river water. Comparing natural to actual water concentrations of various chemicals reveals the human impact on the chemical nature of our surface water. (Table 1.4)
The human touch has left its mark. From industrial heavy metals to acid rain, from leaking storage tanks, accidental spillage, and domestic sewage, to municipal waste and agro-industrial effluent, people and water definitely do mix. Besides affecting the quality of drinking water, secondary impacts have become common. For example, the discharge of organic material, high in nitrogen and phosphorous, into surface water fosters abnormal and explosive plant growth depleting oxygen and affecting the entire ecosystem and the life forms it supports. Twentieth century ecosystem degradation has resulted in the loss of 50% of our wetlands and 20% of our fresh water species. (Table 1.5)
The river waters can not be separated from solid and particulate sediment. Some of this exists in the river beds, disturbed and activated by flows and floods. Much exists as suspended matter, actively in motion. In fact, more than 50 billion tons of suspended sediment is carried by river waters to the oceans each year. What lands in surface water and ground water bodies is increasingly a function of human action and planning. For example, creation of solid surfaces increases volume and rate of runoff, downstream flooding, and human chemical deposits into surface water. Over-mining of ground water impacts water levels and the capacity to live off the land in stressed locations around the world. High surface runoff carries with it expanded sewage runoff in urban environments. Poor liquid waste disposal and hazardous chemical spills travel rapidly above the ground and easily penetrate below the ground in many locations. And as these collective actions impact lakes, rivers and streams, habitats and species diversity declines.
There is then a natural, interconnected, and crucial water cycle upon which all life on earth depends. Humans have always required a dependable water supply to survive and thrive. As we have grown in numbers and in concentration; as we have built and infiltrated among, and at times, in opposition to other life forms, we have created future health challenges that must now be addressed. To do so, each of us must better understand the nature of water, and its relations to weather, ecosystems, agriculture, industry, urban planning, sanitary systems, and value of Integrated Water Resource Management (IWRM).