Stormwater lessons from Southern California – Introduction

An underground cistern in Studio City, California. Source: Southern California Water Committee.

This is the first in a three part series by MPC research assistant Matt Nichols.

Considering their very different climates and histories, southern California might seem like an odd source of inspiration for the Midwest when it comes to innovative water planning.  Additionally, the Los Angeles River – a habitat more suited to filming Hollywood car chase scenes than supporting wildlife – has long been an example of an urban watershed subsumed by grey infrastructure. However, the urgent water crisis in southern California has spurred recent stormwater management efforts that should serve as a model for the rest of the country.  The Southern California Water Committee’s 2012 report, Stormwater Capture: Opportunities to Increase Water Supplies in Southern California, offers a glimpse at the feasibility of implementing green infrastructure projects in an urban setting not unlike Chicago.

Los Angeles and Chicago are both large, coastal cities, but while Chicago has always relied on Lake Michigan for the majority of its potable water, L.A. does not have the benefit of abundant fresh surface water.  Thus, nearly the entire water supply for its 17.6 million residents must come from groundwater.  Considering the region’s rapid population growth – as well as its arid climate and heavily paved environment – drawing down aquifers faster than natural processes can recharge them is a serious concern.  It’s a concern that many communities in Chicagoland’s Northwest Water Planning Alliance (NWPA) share, because they constitute the 19 percent of municipalities in the region that obtain their water from aquifers, not Lake Michigan – aquifers that are also at real risk of going dry in the coming decades.

When it does rain in southern California, it typically rains heavily, so much so that flash floods, serious erosion, and even mudslides are not uncommon along creeks in the foothills above Los Angeles.  This pattern of long periods of dryness punctuated by severe rain events should sound familiar to Chicagoans.  It’s exactly what we experienced during 2012’s record-breaking drought, and unfortunately, we can probably expect more summers like it due to a changing climate. This is all the more reason to invest in green infrastructure that helps us make the most of our finite water resources and prevent costly flooding during major storms.

Southern California is taking steps to do just that, using municipal permit applications as a tool to require more efficient use of water resources. To obtain the necessary permits for new construction or a major renovation, developers in Southern California must demonstrate a plan to “infiltrate, harvest and re-use, evapotranspire, or bio-treat a specified volume…of stormwater on-site” using low impact development (LID) techniques. Of those multiple management options, the mandate to “infiltrate” water is arguably the highest priority for Southern California due to the tenuous state of the region’s aquifers. Reusing rainwater on-site for non-potable uses like watering landscaping or flushing toilets works toward the same goal from the opposite direction: decreasing demand for potable water by substituting an appropriate, under-utilized resource.

Green infrastructure is not a one-size-fits-all solution to water supply and stormwater management issues on a regional scale, but rather a diverse toolbox that can turn under-utilized elements – or even potential liabilities – in the urban environment into real assets.  The next installment in this series will examine how some of those tools have promoted groundwater recharge and water reuse in Southern California – and how we could do the same in Chicagoland.