Lucy Tait of Arlington, Virginia, writes:
Every time I turn on the TV, I see something about a flood or a drought somewhere in the world. Do we really have a water scarcity issue when there is so much flooding? And is there anything we can do to even out the flooding and droughts?
Jeff Opperman, of The Nature Conservancy's Global Freshwater program replies:
The world is so vast, with such varied climates and weather patterns, that both droughts and floods can always be found somewhere on the planet. And at that global scale, the huge volumes of floodwater in one place can't "make up" for the excessive dryness in another place. So some regions of the world suffer from water scarcity even as other regions contend with too much water.
The recent big floods in Pakistan, Australia and Brazil do not change the stark reality that many parts of the world are severely straining their water supplies. Even more concerning, scientists predict that some currently water-stressed places will become even more prone to drought due to climate change, including regions, such as sub-Saharan Africa and India, that still have high population growth rates.
One of the more challenging—and counterintuitive—impacts from climate change is that many regions may experience an increase in the frequency of both droughts and floods. With warming temperatures, rainfall patterns are predicted to become increasingly "flashy"—that is, much of the year's total rainfall will be concentrated in more intense downpours, with longer intervals of dry weather in between the deluges.
These occasional intense floods will increase risks for people and may only temporarily relieve drought conditions, just as the current Australian floods may be just a short departure from that continent's chronic challenge of water scarcity.
How can we deal with these various water challenges? A key strategy will be maximizing the use of "green infrastructure"—such as forests and wetlands—to complement existing traditional infrastructure, such as dams, reservoirs and levees. For example, floodplains along rivers absorb floodwaters and so protecting or restoring these important ecosystems can reduce flood risk for other areas.
Ensuring that land is well managed can also help offset a "flashier" rainfall pattern. Forests tend to soak up rainfall in their soil, while rainfall tends to rapidly run off of degraded land. Thus, planting a forest on overgrazed grassland will increase the amount of rainfall that infiltrates into the soil. Rather than quickly running off the land, contributing to flooding, this water can now slowly move through the soil and into streams to increase their flow during dry periods. Wetlands also store and slowly release water, helping to even out extremes of rainfall.
The Nature Conservancy is promoting conservation projects that will help society cope with challenges of both too much and too little water. We work to protect or restore floodplains and are advancing the concept of water funds, which generate revenue to support land management practices that protect drinking water supplies.