WaterManaging urban stormwater runoff better

As meteorologists monitor the El Nino condition currently gaining strength in the Pacific Ocean, Californians look with hope to the much-needed rain and snow it could yield. But if Californians are going to make the most of the precipitation, they need to put a LID on it.

LIDs, or low-impact development technologies, mimic pre-urban stream functions. Examples are green roofs that absorb and evapotranspire rainfall; rainwater tanks attached to homes and other buildings; and permeable pavement for roads, driveways and parking lots. Rainwater could even be used in the home for toilet flushing and laundry.

These are just some of the strategies suggested by an international group of experts who recently collaborated on a review article in the American Chemical Society journal Environmental Science & Technology.

UCI reports that Stanley Grant, senior author of the paper and professor of civil & environmental engineering at the University of California, Irvine, brought together academics from three UC campuses (UCI, UCLA, and UC San Diego) and Australia’s University of Melbourne; water managers from Orange County Public Works; and engineers from consulting firm Michael Baker International to examine how urban population centers could better meet water supply needs while protecting natural stream ecosystems.

“This team offers a key example of the significant role that University of California scientists can play in finding innovative solutions for major state problems,” said co-author Lisa Levin, a Distinguished Professor at Scripps Institution of Oceanography. “With drought so pervasive, California cannot afford to waste its precious stormwater; nor can it afford to send contaminants into the ocean. The options addressed in this article tackle both of these issues.”

Managing stormwater runoff in urban environments is a challenge for engineers and water officials. During pre-industrial times, rainwater gradually seeped into the ground and, from there, into rivers, lakes and oceans. Humans, however, have replaced forests and grasslands with a lot of impermeable surfaces that send runoff in a torrent directly to the closest waterways. “The massive volumes and pollutants associated with stormwater runoff are a deadly one-two punch for streams and lead to a condition known as ‘urban stream syndrome,’” said Asal Askarizadeh, lead author and UCI graduate student in civil & environmental engineering.

Symptoms include erosion, flooding, and rising stream temperatures; an imbalance in nutrients, carbon and oxygen in the water; and an increase in unwanted sediments, chemical pollutants and human pathogens.