Environmental ethics must give special attention to the water needs of the poor.
Humans obtain the majority of the water they use from their local drainage basin or watershed. People often collect that water by extraction from sub-surface aquifers (groundwater wells), direct diversion from rivers, and removal from reservoirs or retention ponds. Groundwater provides 20% of water for all uses worldwide. In Europe, groundwater provides between 50 and 70% of the potable water. In the United States, 75% of municipal supply systems draw from groundwater. The majority of countries outside the tropics rely on groundwater for agricultural production. In Saudi Arabia and the Libyan Arab Jamahiriya, 90% of the water used in agriculture is drawn from groundwater. India has nearly this degree of reliance at 89%, followed by Tunisia (85%), South Africa (84%), Spain (80%), Bangladesh (77%), Argentina (70%), the United States of America (68%), Australia (67%), Mexico (64%), Greece (58%), Italy (57%), and China (54%).
Human reliance on groundwater resources in many regions is so extensive that the rate of extraction greatly exceeds the natural rate of replenishment through the hydrologic cycle. This causes various problems. Rapid removal of water from aquifers has resulted in serious water shortage and health problems in countries like India and Bangladesh where the demand for water to irrigate crops has been so great that it has been necessary to dig deeper wells for potable water. The deep wells bypass the rechargeable layers of soil where water is naturally purified, and reach into non-rechargeable layers containing water which is sometimes contaminated with arsenic. Likewise, as the water table drops, many poor farmers’ hand-dug wells run dry and they are unable to afford to dig a deeper, bore well. Unfortunately, many families have lost their basic livelihood and slid into poverty this way.
Another problem occurs in regions resting over limestone formations. Limestone geology contains large subterranean caverns that hold groundwater. This is called karst topography. Excessive extraction of groundwater can result in the collapse of the cavern and the sinking of surface layers, creating sinkholes sometimes large enough to swallow up buildings (see Figure 14). From 1972-2000 over 42 Karst sinkholes opened underneath homes and roadways in Moscow, Russia alone.
The ethical ‘value of sustainability’ must inform how we use water so that it remains available for future generations.
River diversion provides water to areas that are without natural water sources. Because river flow is uni-directional, river diversion also reduces water availability to those living downstream, or can cause the water level downstream to fall so low that lake and river ecosystems can suffer or collapse. The Colorado River in the western United States, for instance, no longer flows into Mexico due to a century of water diversion by seven U.S. states. This has deprived Mexican people of water they had relied on for centuries.
Artificial reservoirs are created by damming river water into an artificial lake. Reservoirs are created for three main purposes: 1) for hydroelectric power production, 2) for flood control and 3) as a reliable water source for local communities. While reservoirs make water more accessible for local human use, they can create several local as well as down-stream water shortage problems. Primarily, dam construction increases the surface area of the retained water. This means that more water is directly heated by the sun and subsequently lost through evaporation. In every decade since the 1970’s, the amount of water lost through evaporation from reservoirs worldwide has exceeded the amount of water used for domestic and industrial consumption. Dams can also prevent nutrient-rich sediments from being transported downstream where they are necessary to build river deltas and maintain the fertility of floodplain soils. Water held in the reservoirs for use during low water periods can greatly reduce the water source to communities living downstream.
Finally, as reservoirs fill, they submerge dry land and its plant cover. Once submerged, the plants die and bacteria decomposes the plant material producing methane, a potent greenhouse gas. The decomposing vegetation can provide the ideal conditions for bacteria to convert elemental mercury (Hg) to methyl mercury (CH3Hg). This latter form of mercury is toxic to wildlife and humans. Even small amounts of methyl mercury in fish consumed by humans can impair the nervous system, especially in the developing fetus.