The Wonder Down Under

We live in a valley surrounded by hills, crisscrossed by Alameda Creek and numerous arroyos, dotted with thriving cities and flourishing vineyards. All this is part of our watershed-the land over which water flows on its way to the Bay, or percolates down to the Livermore-Amador Valley Main Groundwater Basin.

Called the "ultimate recycled resource," this water has been reused and recycled over the millennia. That gushing from your kitchen tap, in fact, comes from the same overall supply that mastodons drank from prehistoric lakes. Thanks to the hydrologic cycle, it continually evaporates, travels through the air as water vapor, and falls back to earth as rain, snow, sleet or hail, to begin the cycle all over again.

But as water recycles through Nature and flows across our Upper Alameda Creek Watershed, it picks up impurities, some of which are the direct effect of our own everyday activities. Because we are all part of this interlocking system, our actions can have a lasting impact on the environment miles downriver, or many feet below the earth's surface. During times of high flows, pollutants that find their way into Alameda Creek may reach the Bay, harming fish and other wildlife. During the dry summer months, there is little or no outflow to the Bay, so dissolved solids ("salts") and pollutants remain in our watershed and adversely affect our groundwater-the Valley's single most important local source of drinking water (see box).

GROUNDWATER AND NATURE'S WATER CYCLE

Contrary to popular images, groundwater is not found in underground rivers or lakes. It is stored in porous formations (aquifers) made up of sand or gravel, with layers of silt or clay above and below. As it travels through the aquifer, groundwater may come to the earth's surface in a spring or swamp.

As an important part of Nature's hydrologic cycle, groundwater is continually replaced by a supply that percolates downward from the surface, either naturally or intentionally. Just a few of the ways water reaches the basin are natural recharge from streams, as water percolates through sand and gravel in the stream bed; crop and landscape irrigation; and manmade percolation ponds and injection wells.

Years ago, groundwater was considered relatively impervious to pollution, because it was believed that the soil above filtered contaminants. Within the past 20 years, however, major advances in chemical detection have shown this is not the case. Just like our more readily observed surface waters, groundwater also must be protected from pollution.

One of the many remarkable aspects of living in this valley is that we work and play on top of a major water source. Beneath our feet lies a vast underground basin that stores over 225,000 acre-feet of usable groundwater. (An acre-foot is approximately 326,000 gallons, enough water to serve the indoor and outdoor needs of one to two households for a year.)

Our groundwater basin serves as a "savings account" from which water can be withdrawn and replaced. During years of normal rainfall, it contributes about 15 percent of the Valley's supply. In the event of a prolonged drought, enough water can be stored there to supplement surface water supplies to meet the needs of the entire population for seven years or more.

But just because it's out of sight doesn't mean it should be out of mind. Once groundwater becomes contaminated, it is difficult and costly to clean. We can ill afford to abandon such a valuable source of water, which would only place that much more pressure on heavily tapped surface supplies.

The bottom line? The actions you take above ground have a direct impact on surface and underground water sources. By protecting one, you're protecting both!

Pesticides and fertilizers, oil and grease, soaps and detergents. . . all are products of everyday life, and all can wind up in our surface water and groundwater supplies.

You've seen the stenciled warnings near many gutters: "No Dumping! Drains to Bay." Those grates on the gutters lead to storm drains that carry excess water from streets and yards directly into Alameda Creek and local arroyos, with no treatment. Not only is this water then channeled to the Bay, it also percolates down to the groundwater below. Whether deliberately dumped into a storm drain or accidentally washed into the gutter by rainfall or over-irrigation, pesticides, oil and other pollutants can reach both surface water supplies and our groundwater basin.

Residential landscaping is a source of pride here in the Valley, with its lush green lawns and showy gardens. How you control pests and irrigate your landscaping can have an impact on water quality. Below are just a few of the steps you can take to make your yard and garden watershed-friendly.

Physical and cultural controls are your first line of defense against pests. These simple measures literally bar pests from your garden-or give them the boot.

The key is moderation. Studies have shown that many homeowners apply at least twice as much water as their lawns and gardens actually require. Not only does overwatering wash pesticides off plants and leach fertilizers out of the root zone and into water supplies, it results in shallow, unhealthy root systems. Overirrigated grass grows faster and must be mowed more frequently. Overwatering encourages diseases, which require chemicals to control. Plus, it wastes a precious resource!

Evapotranspiration (ET) is the amount of water evaporating from the soil and transpiring through the leaves of plants. By predicting how much water is leaving your lawn, you'll know how much is needed to replace it. ET figures vary according to the type of plant, temperature, soil type and other variables, but the California Department of Water Resources has developed some basic information to help homeowners determine how long to leave lawn sprinklers on. An ET watering chart and directions for performing a sprinkler system audit can be found in a Sunset magazine reprint ("How Much Water Does Your Lawn Really Need?") available from Zone 7 Water Agency. ET information specific to the Tri-Valley area can also be found on Zone 7's web site (www.zone7water.com).

Other choices you make around your home can affect our water supply and surrounding environment.

We all know they cause air pollution-but did you know cars are a major source of water contamination? Particles contained in exhaust fumes are picked up by rain or drift earthward, to be washed off streets and into Alameda Creek and local arroyos. Likewise, leaking fluids and toxic residue from tires and brake pads become storm-water pollution.

Zone 7 Water Agency has numerous public committees and programs aimed at managing and protecting both surface water and groundwater supplies.

Zone 7 recently took responsibility as the lead agency working toward protection of the Alameda Creek Watershed. The Alameda Creek Watershed Management Program is guided by a steering committee made up of many interested parties who meet the first Wednesday of each month at 1:30 p.m. in the Zone 7 Board Room (5997 Parkside Dr., Pleasanton). The public is invited to attend.

This brochure was produced as part of a grant to Zone 7 to inform the public of the local groundwater resource and what can be done to protect the watershed. The grant project includes activities such as workshops, field trips, school programs and presentations to civic groups. The grant, which is a share of funds from the U.S. Environmental Protection Agency to the State Water Resources Control Board, is administered through the Regional Water Quality Control Board.

Additionally, Zone 7's Groundwater Management Program helps ensure that acceptable water levels within the basin are maintained by artificially recharging (refilling) the basin and monitoring water levels. A Groundwater Management Advisory Committee (GMAC), made up of local citizens, was formed by Zone 7 in 1995 to address groundwater-related issues that could potentially impact the Valley. Zone 7's Salt Management Program further safeguards groundwater quality, as does its well-permitting program, which provides an early warning system for toxic sites within the basin.