Mitigating Drought Impact through Rainwater Harvesting

On June 16, NASA released satellite data that shows we are depleting more than half of the world’s largest aquifers at a rate greater than they can be replenished.  If you’ve ever used well water in your life, it has come from an aquifer.  At the same time, California is in the midst of an unprecedented four year drought that is placing significant strain on reservoirs throughout the state.  What is happening above ground in California is happening below ground the world over.

How did water scarcity become so important to California and the world and what can be done about it?  There are several factors that are contributing to this shortage of drinking water.  The two principal causes are the increasing effect that climate change is having on extreme weather events, such as droughts, and the clean water demands of an ever increasing population.  But there is a third factor that, while less significant, contributes to the decline in aquifer reserves around the world, though it could be turned into a solution with the proper policy and financial incentives.  This factor involves the removal of rainwater from impermeable surfaces, such as roads and buildings.

In the United States, legislation to encourage harvesting rainwater is virtually nonexistent outside of Rhode Island and a handful of other states. Arizona, one of the driest states, had a tax credit equal to 25 percent of the cost of the rainwater system until it lapsed in 2012.  Collecting rainwater is so marginalized, in fact, that it is even illegal in states like Colorado, where a principle known as prior appropriation is written into the state constitution to protect existing water rights.  This is a natural resource that the environment, quite literally, dumps on our heads.  It is estimated that a 1000 square foot roof will collect 600 gallons of water from a 1-inch rain storm.  And yet, this is a free resource that we can’t get rid of fast enough.  What lands on the roofs, roads, and sidewalks in a city of thousands of buildings is promptly carried by gutters and then storm drains underground.  From there the runoff is dumped into the nearest body of water having gathered a myriad of pollutants along the way.  What was originally a relatively clean source of water that could be repurposed for residential or commercial use is discarded as a waste product.

This is where the problem of rainwater disposal could be turned into part of the solution for drought mitigation.  Instead of viewing rainwater as waste to be discarded, homeowners, companies, and municipalities could be conserving rain to their benefit.  For the residential homeowner and commercial businesses, installing a cistern near your building could provide a significant source of landscaping water during the drier months of summer.  Fitting that system with a filter would provide you with a significant source of drinkable water during the warmer months of the year and lower your monthly water bill.  For municipalities, rainwater can be collected from public buildings and used to recharge local shallow aquifers through the use of infiltration basins or injection wells.

Making more efficient use of this limited resource could collectively save individuals and governments billions of dollars in construction of deep wells, municipal water treatment, and expensive desalination plants during times of water scarcity.  In addition, collecting and storing rainwater would allow an area to become more resistant to droughts by prolonging the lifespan of local reservoirs.

This is not a unique solution to fresh water availability.  Beginning in 2001, Australia, already the driest inhabited landmass in the world, witnessed the start of an unprecedented 12 year drought.  This crisis caused the Australian government to rethink how they view water.  Instead of water being a cheap and easily obtained fixture of life, the country began to treat water as a resource to be conserved and traded.  Whereas the typical garden rain barrel in the U.S. is 50-100 gallons, it is not unheard of for residents of Australia to have large rainwater cisterns capable of holding 5000 gallons of water at a time.  This has helped the country to preserve the Great Artesian Basin aquifer on the eastern side of the continent and it is currently one of the most sustainable large aquifers in the world.

It is a given in economics that as a resource becomes more scarce, its value increases accordingly.  Does the rest of the United States really have to wait for a financially devastating catastrophe like California’s or Australia’s to institute policies that favor water conservation systems?  As more people come to accept the concepts of climate change and resource scarcity, will legislators develop and implement policies, such as tax credits and project funding, in a greater number of states to preserve this precious resource?  I certainly hope so.