US cities could store billions of gallons of rain a day


In this map, blue indicates high amounts of annual stormwater runoff from urban areas, while red is low. States with relatively high rainfall And Large urban areas such as Texas and Florida are experiencing much greater stormwater runoff than Montana and Idaho, which have less precipitation and less urban coverage. But even if that were possible, no state would want to capture every drop of stormwater that falls on its cities, because the rains also need to replenish nearby rivers and lakes to maintain the ecosystem. Is required.

This measurement of 59.5 million acre-feet of annual stormwater runoff in the US comes from historical rainfall data. But moving forward, climate change is messing with that rainfall in two main ways. Like the US West, the drought here too has been intense, so there will be less rainfall in many places. And conversely, because a warmer atmosphere contains more moisture, rising temperatures result in heavier precipitation when it rains.

“Even in areas that are becoming drier, we're seeing more intense rainfall events,” says Heather Cooley, director of research at the Pacific Institute. “So the number it is generating is actually an average annual number. And we believe there is additional work to be done to look at the impacts of climate change on runoff.”

For example, the atmospheric river that drenched Los Angeles earlier this month was likely worsened by climate change. And L.A., of all places, is really leading the way for cities to better harness available stormwater as highlighted in this new report. Or, technically speaking, the city is doing the opposite—the idea is replace the Pavement with more dirt and greenery, which absorbs storm water.


A plain in Los Angeles, where rainwater slowly seeps into the ground.

Courtesy of Los Angeles Department of Water and Power

L.A. was able to collect 8.6 billion gallons of water from that atmospheric river in just three days, partly by diverting it into giant “spreading grounds” to seep into the dirt. “Across much of the country, we are expecting — and we are already seeing — larger, more intense storms that bring a lot of water in a short period of time, and then longer periods between storm events,” They say. Seth Brown, executive director of the National Municipal Stormwater Alliance, who provided input for the new report. “The trend is growing: let’s live with water, let’s embrace water where it is, let’s manage it and value it as a resource.”