Not a Drop to Drink: Our Shrinking Freshwater Supply

Freshwater is one of humanities most vital natural resources. We can survive for weeks without food but no more than seven days without fresh water. Freshwater is a renewable resource but it is finite. Considering the abundance of water on this planet, comprising 70 percent of the earth’s surface, a freshwater shortage runs counter to general expectations. Previously, I assumed water to be an unlimited resource, as this is a common perception in the United States; but freshwater comprises less than 3 percent of the earth’s water and only 13 percent of that freshwater is in liquid form, (most of it is locked up in ice caps and glaciers). Water use has increased about twice as fast as population growth over the past century. Globally, we already appropriate over half of the available excess runoff and over 1 billion people currently lack access to clean drinking water (Jackson, Carpenter, Dahm, McKnight, Naiman, Postel, & Running, 2001). Groundwater depletion, low or nonexistent river flows, and worsening pollution levels are among the more obvious indicators of water stress (Postel, 2000). The three main uses of freshwater are irrigation of cropland, industrial and commercial activities, and residential needs. On a global scale, environmental policy changes need to be made along with increases in water productivity, especially in these three areas of consumption, if freshwater reserves are to support future generations.

Freshwater is produced by the hydrologic system (the cycle of water as it moves through the environment): water evaporates, falls as rain or snow, passes through living organisms, and returns to the ocean to repeat the process). Groundwater aquifers are large subterranean areas of porous sand and gravel, which are saturated with freshwater. These aquifers are replenished by rainwater and runoff as they filter through soil layers. Groundwater aquifers naturally store about 99% of the earth’s liquid freshwater that is made accessible to humanity by wells and pumping (Jackson et al., 2001). In many regions, groundwater aquifers have been over-pumped due to agricultural and urban demands. Unfortunately, aquifers can become permanently damaged. In costal regions, over pumping can lead to saltwater intrusion as ocean water gets sucked into the vacuum created by receding groundwater. Also, the porous sand and gravel layer, which houses the groundwater, can become condensed from over pumping. This irreversibly shrinks storage capacity and causes surface land to sink. For example, the San Joaquin Valley has sunk 30 feet due to these causes (Miller, 1996). And, as aquifer water levels drop, wells must be dug increasingly deeper to access the water: “A hundred years ago you could drill 5 feet down and water would come gushing out. Today, you'd have to drill 200 feet to even reach the water," Robin Grossinger, of the San Francisco Estuary Institute, says of the Alviso Creek area” (Miller, 1996).

Worldwide, agriculture claims about 70% of the total water withdrawal (Cunningham and Cunningham, 2006). After the Second World War, developed countries made major advances in irrigation technology, namely sprinkler and drainage systems. The most efficient form of irrigation is the drip system, which has the potential to double crop yield per unit of water, but it is only used in about 1% of the world’s croplands. Many farmers are reluctant to modernize irrigation systems, as it is expensive and energy intensive to do so. In underdeveloped nations, the funds, technology, and infrastructure necessary for irrigation modernization are lacking. The most common techniques used by these farmers are to flood the entire field or run water in rows between the crops, causing much water to be lost to evaporation and runoff. Additionally, shifting to more water-efficient diets might also ease water demand. Calories from animal products require 4 to 16 times more water than a comparable amount of calories from vegetable products.

In addition to massive water consumption, agricultural and commercial farming pollute water, which in turn diminishes usable water supplies (Postel, 2003). Fertilizer and pesticide runoff from fields, forests, roadsides, golf courses, private lawns, and farms, enter freshwater systems and harm humans and aquatic life. Fertilizers are rich with nitrogen and phosphorus, elements that stimulate algae and plant growth, which can clog waterways and use up oxygen resources in the water, thus depriving organisms of oxygen and killing them. The EPA estimates that 50,000 metric tons of pesticides are used in the United States each year and much of this material washes into the nearest waterway (Cunningham and Cunningham, 2006). Also, commercial livestock produce large amounts of animal waste. This animal waste, also nitrogen and phosphorus rich, often harbor pathogenic organisms that are hazardous to