Soil as a Sponge To Reduce the Impacts of Drought: A Least Cost Water Conservation Opportunity

California is in its third year of a historically acute drought – 2014 was the driest year on record. In compensating for the reduced surface water supplies, Californians are relying heavily on groundwater to get us through the crisis.  Local government land use policies have an important role to play in ensuring this precious water supply does not disappear, thus protecting California’s economy. Soils are critical to this effort.

Understanding the Role of Soil as part of the Working Landscape

The expression “dirt cheap” tells a sad story.  It implies that over the years, our soils (or dirt) have been taken for granted.  Today, understanding and appreciating the many important functions of the soil is crucial.

Permeable soils, uninhibited by pavement or other hardscape, can work magic.  Soil acts like a sponge: soaking up water, filtering out pollutants, and replenishing groundwater supplies.

The California Economic Summit, an organization of California businesses and nonprofits, is now referring to undeveloped land as Working Landscapes.  They are focusing on the economic value of open space for the multiple services they provide: wildlife habitat, agriculture, forestry, recreation, and importantly, soils for groundwater infiltration.

US EPA Factsheet, Protecting Water Quality from Urban Runoff, Feb 2003

It is easy to overlook the value of undeveloped land; far too many communities still do. Revenue from development project proposals catch policy-makers’ attention, perpetuating the sprawl of houses, big box stores, roads, and parking lots on the edge of their communities, paving over undeveloped soils that could otherwise soak up rainwater, filter it, and replenish the aquifers below. The irony in this model is that per acre local government tax revenues from compact development far exceed those from sprawling development on the urban fringe. The Economic Impacts of Development Patterns in the San Joaquin Region Factsheet PDF

Economic Impacts of the Drought

Senior Engineering Geologist, Chris Bonds from the California Department of Water Resources monitors flow rate from a groundwater well. CREDIT: John Chacon/CA DWR

Despite the rains that fell in December, California is still in the midst of one of its worst droughts in recorded history. And it’s likely to persist.

Currently, the drought is negatively impacting California’s economy, from the farm gate, to food prices, to recreation and tourism, to jobs, and more. UC Davis Researchers have estimated the total statewide economic cost of the drought in 2014 to be $2.2 billion.

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The water shortage is also hitting many households in the pocket book. Water bills are outpacing inflation, rising more rapidly than home heating and cooling costs.

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For the sake of our State’s economic well-being, we must make every effort to capture and store the rain when it does fall.

Groundwater: A Low Cost Water Collection and Storage Opportunity

Droughts (and floods) have always been part of life in California. But climate projections forecast increasing frequency and severity of those droughts. If California is to continue growing, our economic future depends upon using water wisely, and stretching our existing supplies to the max!

It is groundwater – nature’s own savings account – that is helping us weather the current crisis.  Compared with reservoirs and desalinization plants, increasing groundwater recharge is by far the least-cost option for improving our water supply reliability. Replenishing our dwindling groundwater reserves – by putting water back in the ground – costs roughly half as much as building a new dam, and costs 1/3 as much as building a desalinization plant.

Overused; California’s Groundwater is in Crisis

Electric pumps take groundwater out faster than it can be naturally recharged. Image public property, Department of Water Resources

In the past, natural recharge was enough to maintain a balance between water pumped out of the ground and surface water – from streams and precipitation – percolating back into the aquifer. But beginning in the 1920s with the arrival of powerful electric pumps, Californians started taking water out of the ground faster than nature could put it back in.

In order to restore this balance, we must use our water more wisely. By increasing conservation, and implementing new technology for water use efficiency, we can greatly reduce the insatiable demand for groundwater supply. However, conservation and technology alone cannot reverse the deficit we have created.

Some regions of the state are withdrawing groundwater at twice the rate of natural recharge. To make matters worse, many of the open spaces that could help refill aquifers continue to be covered over with houses, roads, and parking lots. We must reverse this trend to ensure that nature is able to do its job.

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We are living off our reserves. And just like a savings account, ignoring our rate of withdrawal is perilous.  According to UC Irvine professor Jay Farmiglietti, “People need to truly understand groundwater is disappearing. Without intervening, that water is not coming back.”  When groundwater is depleted, the land subsides – essentially dissolving that sponge. Once groundwater storage capacity is lost, it cannot be recovered.

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The Critical Role of the Ahwahnee Principles

The Ahwahnee Principles provide a blueprint for regional sustainability. Providing suggestions for how and where we grow, the Principles prescribe compact, walkable, water-use efficient urban growth that preserves open space.  This growth pattern allows permeable soils, uninhibited by roads, houses and parking lots, to do their job: act as a sponge, soaking up water, filtering out pollutants, and replenishing groundwater supplies.

The EPA has calculated that a compact, smart growth development pattern, surrounded by non-urbanized open space, can reduce runoff by two-thirds compared to low density, sprawl development.  But once impervious surface coverage exceeds 10 percent, the ability of the land to absorb and store water is significantly compromised.  Beyond 10%, the stormwater runoff increases while water percolation through the soil decreases. A study of the 20 regions that sprawled the most over the period of 1982 – 1997 shows that they now lose between 300 and 690 billion gallons of water every year, water that would otherwise have been captured and stored in the ground.  Download the Ahwahnee Water Principles Guidebook

When it comes to our water supplies, land use policymakers must take into account the property value of soil as a sponge: soaking up water, filtering out pollutants and replenishing groundwater supplies.

AB 1739, signed into law in September 2014 will require agencies in charge of groundwater supplies to produce a Groundwater Sustainability Plan.  In the future, when a city or county adopts or substantially amends a general plan, its consistency with a locally adopted groundwater management plan will have to be evaluated.

LGC is holding listening sessions this month to update the 2005 Ahwahnee Water Principles Guidebook to address new regulations.

Local Communities Taking Action to Preserve Working Landscapes

Decisions to preserve a working landscape are made at the local level, often led by cities, counties, local agency formation commissions (LAFCOs) and local water agencies. There are many steps municipalities can take to ensure working landscape soils can collect, purify, and deliver their water to the underground aquifer. Here are some examples:

LAFCOs – established in 1963 and modified in 2000 – are required to “discourage urban sprawl” and “preserve open-space.”  Some LAFCOS have been taking this responsibility very seriously.  For instance:

Kings County LAFCO, in 2007, reduced the area that can potentially be annexed by the cities and community services districts in their region. This has saved almost 11,000 acres of working landscapes from urbanization.

Monterey County LAFCO now requires applicants to illustrate how their proposals will preserve open space and agricultural lands.  Working with landowners, this LAFCO has protected a significant amount of land by negotiating permanent conservation easements and buffer zones.

Cities and counties are also playing a critical role:

More than a decade ago, the Association of Bay Area Governments identified sixteen cities in the Bay Area and Northern San Joaquin Valley that had adopted urban growth boundaries.  Some of these boundaries are permanent; others can only be breached by a vote of the residents.

The Fresno Council of Governments (COG) is developing a “San Joaquin Valley Greenprint” to map the Valley’s natural resources and working lands. The aim of the Greenprint project is to serve as a guide for local land use decisions, and to help municipalities recognize the many public benefits of their natural assets, including groundwater recharge.

Arcata, CA:  A series of bonds floated by the City of Arcata in the first half of the twentieth century helped this innovative community obtain title to 2,134 acres of second growth redwood forest, the source of the City’s water supply. Development in the Arcata Community Forest is prohibited, allowing naturally-occurring low fires to burn, without risking residents’ homes.  The city also removes shallow rooted, highly-flammable vegetation, increasing the likelihood that deeply rooted trees, (which use less water) will help deliver their precious water resources back to the aquifer.

Through careful management, the Arcata Community Forest generates annual revenue through sales of forest products of $500,000 to $700,000 – more than is needed for it to be self-supporting.  At the same time, the community enjoys the cleanest, freshest water possible at bargain rate prices.

Austin, TX:  In Texas, Travis County and the City of Austin – with the assistance of federal funds – are purchasing 600 homes located in a flood plain, at risk from severe flash flooding.  The City and County plan to restore 206 acres adjacent to the creek to their natural state, enabling the land to soak up water, filter out pollutants and replenish groundwater supplies.  Other co-benefits of purchasing this land include recreational opportunities and habitat for a wide diversity of animals.

Growth boundary policies are increasingly becoming common.  The counties of Ventura, Napa, Yolo, and Stanislaus, as well as many of the cities within, have established similar growth planning boundaries.

To make urban growth boundaries feasible, city policies must ensure it is both legal and cost effective to accommodate increasing population in already developed areas through infill development.

Sadly, infill development in most communities today is still more difficult and more expensive than sprawl. To address these barriers to infill development, local jurisdictions need to change their general plans, zoning ordinances, parking and street width standards, and other such policies and permitting processes so that building and renovation in already developed areas is both legal and cost effective for the development community.

Download A Policymaker’s Guide to Infill Development

Addressing the Needs of the Future

A recent study by UC Davis further illustrates the fact that drought is something Californians must learn to live with. In the future, water supplies will become ever more stretched, and the cost of delivering that water will continue to rise. It is critically important that we implement low cost strategies for capturing rainwater and ensuring it recharges our aquifers.  Maximizing the role of the soil as a sponge and preserving our working landscapes that soak up precipitation is a feasible, least-cost opportunity for assuring future water supply reliability.

Special acknowledement for this issue of the Livable Places Update goes to LGC Founder, Judy Corbett as the main contributor to this article.