As the global demand for limited resources of fresh water increases, it seems obvious to turn to saltwater resources and desalination technology. Still, there are other considerations to make when evaluating the viability of desalination plants, just as there are for resources like fossil fuels or someday, even nuclear fusion. In fact, debate on these resources eventually comes down to a fairly basic set of questions:
Is the Source Renewable and Sustainable?
The global demand for freshwater resources is clearly unsustainable. As the world’s population grows and our industrial and agricultural activities increase to support that population, we have seen that freshwater sources such as rivers, lakes, and aquifers are extremely limited and vulnerable to overuse. Moreover, these sources are part of a deeply interconnected web of ecosystems, which means that damage to one part has a cascading effect far beyond what we can predict or even detect in the short term.
In most cases, while the water we use will eventually find its way back into the global ecosystem, the natural hydrologic cycle is substantially slower than our current rate of consumption. Barring any discussion of permanent contamination of water through other industrial processes, it’s reasonable to presume that the abundance of water on our planet is sufficient to meet our needs for the foreseeable future. Therefore, the issue is less that there is insufficient water available on the planet, rather that we have a flow problem, i.e., not enough fresh water is cycling through the system fast enough.
The most abundant source of water on Earth is clearly our oceans and seas. Purely from that perspective, ocean water appears to be an ideal resource for meeting our global needs, even if it is not immediately available in a usable form. We deal with many resources that require some form of processing (everything from processing iron ore to preparing Cassava for eating, for example) so it’s not unreasonable to consider a similar requirement for water.
What Are the Environmental Effects?
Harvesting Salt Water
Withdrawing saltwater from oceans doesn’t appear to be a concern with environmental scientists around the world, so long as collection spots are well distributed and collection methods designed for the least physical effect on vulnerable ecosystems. In fact, some scientists argue that large scale collection of ocean water and subsequent sequestration on land could help mitigate concerns about rising sea levels and associated reductions in ocean salinity. Certainly, the growth of desalination plants is insufficient to compensate for the enormous volume of water stored in the world’s ice caps, but it’s helpful to consider that the likely overall effect on the world’s oceans will be minimal.
Brackish water is another source targeted by desalination plants. Brackish water is generally found in underground aquifers that have been infiltrated by seawater or that exist in geologic formations that are naturally salty, such as those near ancient seabeds. Brackish water has a lower salinity level than ocean water, but it is still unsuitable for human consumption. While it seems to be to our advantage to clear out aquifers that hold “unusable” brackish water, this can be a risky process - sometimes ocean water is pulled into the void left as brackish water is withdrawn. In other cases, emptied aquifers may simply collapse. It is also difficult to predict the long-term effects of wholesale withdrawal of underground brackish water resources from the global ecosystem.
Salt and brackish water can also be drawn from sources other than oceans and aquifers, and it is a common byproduct or waste material from many industrial processes. These are not adequate sources, by themselves, to meet our growing demand for fresh water, but the ability to process salt water, extract valuable resources, and ultimately reduce the amount of generated waste is valuable on many fronts. Considering the various available sources for salt and brackish water around the globe, then, let us submit that saltwater as a resource is both renewable and sustainable.
