To anyone who has considered a map of the world it is hard to consider how water is a resource that may at some point be in short supply. Most of what we see though represents the water in the oceans. We may be able to put out fires with it, but we cannot drink it. Indeed, 97-98% of all water on Earth is present in the oceans, some inland seas, and in salty ground waters. We cannot live on salt water unless we first remove its salt Fresh water in flowing rivers fed from either underground sources, glaciers or mountain range hard snow packs represent most of what we drink and use for a variety of needs. In addition, we find reasonably large amounts of ground water, some of it buried very deeply long ago. In some cases as long ago as the Pleistocene age or buried in renewable aquifers more recently. In some cases we dig deep wells to bring it up to feed the crops, hopeful we will not use it up too rapidly or that it will be renewed by water seeping back in from surrounding rock, put there by the rains which come from atmospheric moisture condensed into rain clouds which result in the rains coming back down over the earth. In total, all this fresh water represents a little over 2% of all the water on the Earth. Fresh water flows into the oceans, but the ocean’s waters evaporate when conditions are right, condense in the clouds and come back to us in many areas principally as rain and snow. Collectively, all aspects of natural water movement over the Earth, over land and sea, represents the hydrological cycle. We know a lot about it but to the extent the movement of water around the Earth may become more complex as the Earth warms, we need to know more.
Humans depend on fresh water to live. It is hard to imagine a more precious resource. Unhappily, fresh water is not evenly divided. For our survival we need an unsalted, nontoxic source which does not harbor toxic parasitic organisms.
Human tribes, kingdoms and later nations have always had disagreements over water rights, but have almost always negotiated their joint use. Wars fought over water rights may be equivalent to a death sentence for the losers, who would not live for long absent access to fresh water.
While only about one 50th of the fresh water on land is usable, this is actually a lot of water, but, of course, the water is not equally distributed over all of the lands on the Earth. In some locations the hydrological cycle will not bring it back to us as fast as we use it. These may be areas where rains from ocean storms are not plentiful, or where we, in fact experience long periods of drought; or years with few rains to bring the used water back to us. Some Scandinavian countries for example may have as much as 100 times as more reusable fresh water as some countries in Central Africa.
As the population of the Earth has risen issues of water availability and distribution become increasingly important. More people will use more water, and supplies will have to rise when, in many cases, they are dwindling. With the absence of summer ice in the Arctic, we see more precipitation in the northern hemisphere, but also more warming and the gradual removal of glacier ice and snow pack. Major rivers around the world are slowly losing their capacity to provide fresh water supplies to cities or groups of cities with increasing populations. Aquifers with low replenishment rates are drying up.
Serious attention needs to be paid to recovering large amounts of desalinated water from the seas and creating a means for distributing it to those in need. While this is already beginning to happen in some locations a more comprehensive and thoughtful plan will clearly have to evolve to address the developing problems in many locations where conditions are serious if not dire already. Water availability also affects the ability to grow crops to provide food, as well as our current ability to generate the energy we need.
As the century proceeds there are many issues related to the ready supply of fresh water which become even more critical even while they are obvious now. We will consider some of these maters in later posts.