Select Page

California Case

When winter 2016-17 brought extraordinary rainfall to California, following punishing years of drought, many decried the lack of storage facilities to capture some of that excess, frustrated that opportunities for new dams are limited, often fraught with complex environmental conflicts and, especially, daunting costs.  

During the preceding drought years, the “race to the bottom” in groundwater pumping caused likely irreversible loss of aquifer storage space in some basins.   Our own “Tragedy of the Commons” precipitated California’s  historic 2014 Sustainable Groundwater Management Act (SGMA).  

It simultaneously revealed just how dependent on groundwater we really are, with impacts beyond just water supply quantity and aquifer capacity.  Land subsidence due to “too many straws” penetrating deeper into the aquifer has also impacted the integrity of Central Valley Project infrastructure.

Perhaps partly because implementation of SGMA, ongoing as Rainfall to Groundwater emerges, has been necessarily rapid, certain sound, cost-effective  strategies for maximizing groundwater recharge have been overlooked.  

A larger influence seems the recalcitrance of 20th Century engineering paradigms that blind their adherents to other opportunities.  After all, that paradigm may best be encapsulated as “moving water off the land as quickly as possible”.  It doubtless takes some time to shift gears.  

Other strategies have been proposed, namely this one, but apparently require a broad-scale paradigm shift to be fully recognized, embraced and implemented.

Rainfall to Groundwater aims to facilitate that shift.  See Alternate Paradigms.

As we emerge, the prevailing notion of water storage remains dams and surface water reservoirs, which have their limitations, as noted above.

Recognition of “the soil profile as a natural reservoir” (Hursh and Fletcher 1942) has been lost to collective memory.  Rainfall to Groundwater aims to bring it back to full consciousness and action to benefit us all.

Key is understanding the difference between Retention vs Detention Storage.

The basic idea is that we restore detention functions to historically degraded watersheds aka catchments.

Route more precipitation into the ground right where it falls.  Attenuate peak flood flows by enhancing infiltration and percolation on watershed uplands, as well as along the drainages, so that some of that excess otherwise “lost to the ocean” during winter will stick around into summer to help sustain groundwater and baseflows.  And fend off seawater intrusion where applicable.


Restoring appropriate native vegetation to historically degraded watersheds will restore detention functions over time.

It will doubtless be the least expensive and most sustainable option for augmenting groundwater recharge.  

Evidence suggests that such work could begin to enhance groundwater recharge and baseflows relatively quickly in some cases – within five years or so.  

But the native woody and perennial root systems, associated soil ecosystems and the detention functions they confer will continue to develop and evolve over decades and centuries . . .

Expanding the storage capacity of the vadose zone “sponge” far into the future . . .

California is our initial case study because that’s what we know most about here at Rainfall to Groundwater.  But we’ve considered some other landscapes.  

If you’re outside California and anything here rings a bell with you, please make your own extrapolations.  And let us know about them!  Contact


Opportunities to Restore Detention Storage

In California the most obvious, expansive example of historically degraded lands is nonnative annual grasslands, dominated by Mediterranean-origin grass species brought here by Europeans.

California’s “golden, rolling hills” (Kate Wolf 1977) are among the prominent landscape features of northern and central California especially, occupying smaller portions of the “southland”, as well.  They are recognized by their bright green in winter, fading to gold and beige as the land dries out by summer and fall.

According to the The California Gap Analysis (Davis and colleagues 1998), the total area of nonnative annual grasslands in California is surpassed only by cumulative agricultural cover types.  

Nonnative annual grasses have also come to dominate oak woodland understories, altering their detention functions, among other ecological and ecohydrological relationships.  

So ample opportunities are available to expand water storage by restoring degraded watershed detention storage functions – especially (coincidentally?) within the watersheds of overdrafted groundwater basins who have recently established Groundwater Sustainability Agencies, pursuant to developing Groundwater Sustainability Plans under California’s Sustainable Groundwater Management Act.

California Native Plant Society colleagues would point out that those nonnative annual grasslands may host relictual native species of some importance.  Such instances must be documented and considered in restoration planning.  They may hold important clues to potential vegetation.  But in general these current rangelands represent, at most, mere echoes of what once was.  

Especially ecohydrologically.

Those imported annual grasses were pre-adapted to California’s Mediterranean-type climate of wet winters / dry summers.  Likely also to imported European land management styles.  

And they took over wherever the land was disturbed – by managed (or not) burning, physical removal of trees and shrubs, even natural disturbances.  And by plow when dryland wheat farming briefly became the new Gold Rush.  Until the land gave out.

Their human-facilitated conquest of the land coincided with the decline of native soil ecosystems and the detention functions they afford.


Vegetation Restoration Goals

A common assumption is that lands currently clothed by California’s nonnative annual grasslands were prehistorically covered by perennial grasslands.

Verna recalls Jon Keeley’s 1992 presentation, “Native grassland restoration: the initial stage – assessing suitable sites” (published 1993) as the first to publicly question that assumption, correlating natural vegetation with soil types and other environmental factors.  

At the time, Environmental Impact Reports routinely accepted restoration of perennial grasses as mitigation for impacts to nonnative grasslands.  Perhaps some still do – ?  

But that was just as, expedited by listing of the California gnatcatcher, coastal sage scrub restoration became all the rage, applied to many existing annual grasslands in southern California – in recognition that these actually represented historically degraded shrublands.  Combined conservation and regulatory impetus.

While it’s unclear how broadly this awareness penetrated the culture as a whole, it absolutely enlightened Verna’s perspective from the moment she heard Keeley’s talk.

Couple that with her own field exposure and learning some of the history and even prehistory of human land management and one wonders whether she would even recognize California prior to all human influence.

See California “Grasslands” vs. Altered State(s) for more on vegetation considerations, see blog post 4. Think Outside the Basin for more on historic and prehistoric human influences.

Restoration of native vegetation types, especially including woody species, for the detention functions they catalyze must be based upon sound site analyses and correlation of site features and influences with what is known about suitable vegetation.  This will be the foundation of sustainability, as well as of watershed/ catchment functions.  And then adaptive management must see the transition onward to self-sustaining landscapes within human ecosystems.

Much will not be known at the outset but Rainfall to Groundwater offers strategies for embracing the unknown, adaptive management, among others.

See Learning Program Vision and Collaboration & Play.

California Ecohydrological Economics:

What’s in this for water users?

What’s in this for ranchers?

Why might farmers, others voluntarily relinquish riparian and floodplain lands?

What’s in it for steelhead & salmon?  mentions the Salinas River, whose greater watershed/ catchment is among those most likely to benefit from the Rainfall to Groundwater approach.

See more under Ecohydrological Economics

Especially see, Who owns the Rainfall?  A legal frontier?


Further Reading:

Davis, F. W., D. M. Stoms, A. D. Hollander, K. A. Thomas, P. A. Stine, D. Odion, M. I.
Borchert, J. H. Thorne, M. V. Gray, R. E. Walker, K. Warner, and J. Graae. 1998.
The California Gap Analysis Project–Final Report. University of California, Santa
Barbara, California, USA.

Hursh, C. R. and P. W. Fletcher. 1942. The soil profile as a natural reservoir. Proceedings
Soil Science Society of America 7:480-486.

Keeley, J. E. 1993. Native grassland restoration: the initial stage – assessing suitable sites.
Pages 277-282 in J. E. Keeley, editor. Interface between ecology and land development
in California. Southern California Academy of Sciences, Los Angeles.