What does a careful analysis of our Mediterranean climate, historic climate patterns, and water supply reveal about our future here in Butte County? Specifically, what does the historical climate record tell us about for precipitation and temperature? How have groundwater levels changed over time? What do these trends and changes portend for our future?
California: A Floristic Hotspot in a Mediterranean Climate
A “Hotspot” is a region that is rich in biodiversity and also threatened with destruction. To be termed a Hotspot, a region must have at least 1,500 species of vascular plants that are endemic (not found in any other location) and must have experienced a loss of at least 70% of its original natural vegetation. In addition, Hotspots support half of all plant and animal species, and more than half of endemic species, on Earth. The California Floristic Province stretches from southwest Oregon to northern Baja, and from the coast to the Sierra Nevada.
Of the five global Mediterranean regions, California has the greatest biological diversity, due to a unique combination of topography, climate, geology, and soils.
Extreme variability in rainfall is the norm for California's climate patterns. Most important is timing: when rain falls (or is absent) throughout the year. A few storms can make all the difference. We receive the majority of our rain (up to 75%) in just five months, and 50% of that in just three months. Atmospheric rivers provide a full 40% of our annual rainfall, and when high pressure ridges (such as the one aptly named the Ridiculously Resilient Ridge) keep these weather events from releasing their load of water onto our thirsty state, we experience one of California's historically common cyclical droughts, as has happened over the last few decades. Recently, droughts have been more frequent and more severe.
Water Supply, Temperatures, and Groundwater
One-third of our annual supply of water for agriculture and urban use comes from the Sierra Nevada snowpack. Frozen water melts gradually as the weather warms, filling rivers and lakes, and replenishing groundwater supplies. This is nature's way of helping us get through our dry, hot summers. We will likely continue to experience a decrease in annual snowpack due to climate change and the associated uptick in average temperatures.
According to NASA, the last decade has been the hottest on record with 2020 tying 2016 for the hottest year ever. In fact, in June 2021 over a thousand daily temperature records were broken, making it the hottest June recorded in North America. Low nighttime temperatures are warming faster than daily maximum temperatures. More nighttime temperature records were broken than daytime highs this June (NOAA,Global Historical Climatological Network). The rise in low temperatures during dormancy has implications for fruit trees that need a certain number of chill hours to produce fruit. Tip: When buying new fruit trees, select varieties that require a low number of chill hours.
As temperatures rise and the snowpack decreases, mountain soils dry out faster. These dry soils absorb more of the snowpack runoff that historically has filled our reservoirs. This spring, runoff was greatly reduced as the dry soils and vegetation soaked up any runoff before recharging our reservoirs.
Groundwater is a crucial resource. The combination of low precipitation and high temperatures is especially damaging to our groundwater supplies. This underground storage system took tens of thousands of years to accumulate. In California, groundwater normally supplies 40% of our water needs. In dry years, groundwater accounts for 50% to 75% of our water use. The Chico urban area is 100% dependent on groundwater, and dry years here result in an even greater reliance on our groundwater aquifer.
Lack of rain and low snowpack means aquifers have less recharge since reservoirs do not fill, rivers have reduced flow, and surface water users have a reduced supply. When rainfall is scanty and snowpack is low, we naturally pump more groundwater for our daily needs. When drought cycles last for several years, groundwater supplies are diminished beyond the normal annual rainfall's replenishment capability. Several wet years are needed to see improvement in groundwater levels.
In a 15-year program that ended in 2017, NASA's Gravity Recovery and Climate Experiment (GRACE) satellites showed that between 2003 and 2013, some aquifers in California were depleted by up to 50% - a direct result of pumping groundwater. In some areas, particularly in the San Joaquin valley, we've consumed twice as much groundwater as has been replenished through rain and snow. In the Central Valley, applications for well drilling permits have skyrocketed, and wells have been deepened. Five wells in Kern County were recently drilled down to 2,500 feet! Practically speaking, well depth is limited by water quality and economics of pumping. At levels below 1,000 feet in the Sacramento Valley, groundwater becomes saline, a result of ancient marine sediments.
To better understand the structure of our local aquifer system, Butte County Water & Resource Conservation formed a partnership with Stanford University and CSU Chico to conduct an Airborne Electromagnetic Method (AEM) survey in 2018. Using a helicopter, the survey took an “MRI” of the ground to map the layers of sand, gravel, silt, and clay down to 1,500 feet. For an awesome video representation of the findings go to: https://mapwater.stanford.edu/. The California Department of Water Resources has an excellent two minute video explaining how AEM leads to a better understanding of our aquifer structures and soil layers.
By measuring the electrical resistivity, the composition of soil layers can be determined, leading to a better understanding of our aquifers and groundwater system. Local well data was used to aid in interpreting these findings. The information is being used to improve the hydrogeologic model for development and management of the Groundwater Sustainability Plans required by California's Sustainable Groundwater Management Act (SGMA). We are very fortunate that Butte County is ahead of the game in implementing SGMA.
Studies completed by the US Geological Survey showed that the water table dropped 100 feet in the Modesto area and 500 feet in the Tulare basin in recent drought years. In some areas of the Sacramento Valley, groundwater levels have dropped up to 13 feet.
In basic terms, the ground deep beneath our feet is filled with sediment, layers of clay, sand, and gravel from ancient lakes and streams. These layers hold water. In some areas, a layer of clay separates the shallow groundwater storage pockets from deeper aquifers. Over-pumping deeper formations can compress clay layers, due to the weight of the overlaying land, and they can permanently lose some of their ability to hold water. This has been particularly problematic on the west side of the San Joaquin Valley. Fortunately, deep monitoring wells in Butte County have shown no evidence of subsidence due to the geological structure of the Tuscan aquifer.
In economic terms, the damage to infrastructure can amount to hundreds of millions of dollars: subsidence damages canals that transfer water; buckles roads and bridges; causes pipeline damage; and can create fissures and depressions in the land itself.
How Did We Get Here?
Why do we plant thirsty plants and large, lush lawns, in a dry climate that is regularly threatened by drought, and irrigate them with a limited resource?
California has over 5,200 species of native plants, of which almost 30% are endemic, having evolved strategies to survive and thrive with sporadic rainfall, and through long dry summers. From wildflowers and shrubs (like poppies, Ceanothus, and manzanita), to our majestic oak woodlands, the Central Valley, foothills, and mountains of California are populated with a rich tapestry of sun-loving, drought resistant plants. But people moving west, particularly in the last century, longed for landscapes that reminded them of home, a look very different from the plants that covered the valleys and hills of California.
In the 1840's pioneers from the Eastern US began settling in California. The Gold Rush from 1849 through the 1850s and completion of the Transcontinental Railroad in 1869 led to a great influx of people from different climates. Settlers from the East arrived with their favorite agricultural seeds and plants tucked into their luggage. Fortunes gained from mining, agriculture, and timber harvesting allowed the development of ornamental landscapes using familiar, yet foreign, exotic plants. The Eastern landscape style brought to California by emigrants originated primarily from northern Europe and the eastern U.S. – where it not only rains a lot, but rains throughout the year.
Where Do We Go from Here?
Currently common irrigation practices and landscape designs are not sustainable. We've only gotten by with our present level of water use through our groundwater supply. Once that's evaluated and potentially limited by SGMA, changes will be required. The water resources needed to maintain our landscaping must become balanced and sustainable.
Historically, no one really knew the state of our groundwater supply. With the scientific tools we have now, we have a better grasp of our conditions. Satellite images, tree ring analyses, and AEM technology all give us a much better sense of climate trends, and how they all interact. Because of the latest technology, we can gain a good understanding of the conditions underground. The cool digital visuals allow us to understand in stark terms what's going on with groundwater. We can talk all we want about it, but it really hits home when we look at the graphs.
The UC Master Gardeners of Butte County offer many resources to encourage the shift from water hogging to more appropriate landscape choices. Our website, past and current Real Dirt articles, and Demonstration Garden all provide information and examples for making these changes in your own yard. Particularly helpful resources on our website include a list of Climate Appropriate Plants for the Northern California Landscape and a wealth of tips for Drought and Water-Wise Gardening.
In previous drought years we saw the start of a move to a more sustainable model: converting lawns to drought-tolerant landscaping; turning towards native plants; and minimizing water usage. This is encouraging. Social change moves slowly, but it's beginning. By understanding our climate, hopefully we can learn to garden within our means.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at firstname.lastname@example.org (preferred) or call (530) 538-7201.
By John Smith, Butte County Master Gardener, June 19, 2015
To check your water usage, first locate your meter. Bring a screwdriver, a flashlight, and pen and paper with you. Use the screwdriver (or similar lever-type tool) to wedge into the slot on the “lid” over the meter, and lift it off; then shine the flashlight inside to make sure no black widows or other dangerous creatures are lurking in there. You will probably have to brush some debris off the face of the meter. When you do, you will be looking at a large circular dial, a smaller blue dial, and, below them both, a series of numbers. Write those numbers down. This is the base you will begin with. Once you have those numbers, you can start to calculate your daily water consumption.
Each full number in front of the decimal point on that gauge represents one unit which is 1Ccf or 748 gallons of water. The numbers to the right of the decimal point are in 1/100s (one-one-hundreths) of 748. The larger dial moves clockwise, indicating water use up to 748 gallons; when that number is reached, the full number on the gauge increases by one. The smaller blue dial indicates that water is being used at that moment. If all of your water is shut off, the blue dial should not be moving. If it is, you have a water leak or water on somewhere on your property.
There are several ways to use this information to become a more informed water user and to reduce overall water consumption.
- If you note down the water gauge number late on a night when you are not irrigating, then check the gauge again in the morning, you should be able to tell if you have a water leak somewhere on your property. –If the gauge tells you that water has been used when you have not, to your knowledge, used any water, somehow water is leaking out.
- Test how much water you actually use when hand watering with a hose. It certainly seems like hand watering uses much less water than sprinklers – but does it really? Check the number on your water meter, then, using a stop watch, see how much water you actually use in one minute with the hose on full force. Or see how many seconds it takes to fill up a five-gallon bucket watering can.
- Check that water meter number, then take your usual shower, and check that number afterwards. Subtract the smaller number from the larger and multiply that decimal number times 748. Your answer will be the number of gallons used.
- If you have an automatic watering system, record your pre and post irrigation meter readings, then use procedure above to calculate gallons of water used each time your irrigation system runs.
Those living in the Paradise Irrigation District (PID) have access to a more advanced individual water-usage information system than those with Cal Water. The water meters of PID customers are green (easy to spot). A system known as "Aqua Hawk Alerting" reports water use every hour on the hour. This information is updated online every 24 hours. PID customers can log in online to view their previous day's water use. This system allows users to look at a daily water use graph which is helpful in evaluating the effect of their water-saving strategies. Aqua Hawk will notify customers by phone, text, or email if it detects a possible leak. This system also allows customers to specify an amount of water (in gallons) or an estimated bill amount (in dollars) that they don't want to exceed. If water consumption or bill amount exceeds or is projected to exceed the threshold value,AquaHawk will send a notification. This is very helpful in meeting water budgets.
Cal Water has not adopted this reporting technology, but by logging in their account number online, Cal Water customers can view graphs of their monthly water usage, comparing 2013 and 2014 usage with the newly-reduced monthly targets.
By Eve Werner, Butte County Master Gardener
California Water Service is offering rebates for those in single-family residences who remove lawn and replace it with drought-tolerant plants. This is a great opportunity—it is not difficult to realize landscape water savings of over 80% through careful plant selection, site preparation, and accurate application of irrigation. .
However, the current rules for the rebate require that homeowners complete their lawn removal project within 120 days of gaining approval to start work. Please note that four months is not enough time to properly kill many Chico lawns, especially those which contain Bermuda grass. If the lawn replacement project is started during the summer, the time restriction on the rebate forces replanting during our hot season, which can result in the stress or death of the new plantings.
The optimum time to plant a dry garden is between November, when the first rains begin to fall, and February. Planting during that period gives plants a chance to establish roots before the summer heat arrives, and before the soil begins to dry out.
In the meantime, you can properly kill your lawn. Our next Real Dirt column will explain how to do just that.
By Brent McGhie, Butte County Master Gardener, February 7, 2014
Since this is shaping up to be one of the driest years in California history, it's appropriate to look at ways to conserve water in the home garden. A good starting point is the garden soil itself. Sandy soils tend to drain too rapidly, while heavier clay soils may drain poorly and not provide sufficient oxygen for plant roots. Adding organic compost to the soil will help rectify both of these situations. Organic material increases the water-holding ability of sandy soils and loosens clay soils, so that they are better aerated.
A lawn is normally the single greatest water-user in the home landscape, so unless it serves a specific purpose, such as entertainment, or a play area for pets or children, you might consider replacing it. Lawn substitutes can include planters, ground covers, mulches or hardscape features such as decks or patios. If you choose to have a lawn, the type of turf will affect water use. Warm season grasses such as Bermuda grass, St. Augustine grass, or zoysia grass typically require about 20 percent less water than cool season grasses like tall fescues or bluegrass. Water only when necessary. If you step on the lawn and it springs back when you move your foot, it doesn't need water. Aerating the lawn will maximize water penetration and the duration of watering should be timed so that excess water does not run off of the lawn due to saturated soil. Adjust sprinklers so that water does not end up on concrete or gutters where it is wasted. For lawns and all landscape plants, watering in the early morning hours when wind and temperatures tend to be low means less water will be lost to evaporation.
If you are deciding what to plant, California natives from our climate zone are a good choice. They will need regular watering at first, but can often survive with little more water than they receive from average rainfall after they are established. Try to limit the use of plants that require frequent irrigation and, for efficiency, group them in areas where they can be watered together.
All plants should be watered only when necessary. Check on soil moisture and adjust your watering schedule frequently to reflect seasonal variations in temperature, wind and rainfall. Any plants with similar watering requirements should be grouped and watered with separate valves. Although sprinklers are the best way to water lawns, the most efficient way to water other plants is with drip or soaker hoses. This minimizes water loss through evaporation or runoff. Infrequent, deep watering results in deeper root growth, which in turn allows plants to develop greater tolerance for hot, dry weather. It is important to maintain your irrigation system, checking for leaks, broken sprinkler heads, clogged drip emitters and other problems that could result in wasted water or stressed plants.
A drought year is not the time to engage in excessive pruning. Such pruning can lead to heavy plant growth and a resulting increased demand for water. Light pruning during the winter can shape a plant without stimulating excess growth. And early summer pruning reduces vigor, leaf area and water demand without stimulating excessive growth.
Over-fertilizing can also result in excess plant growth and extra water consumption.
There are several advantages to mowing lawns slightly higher during hot weather. Their growth rate is slowed (reducing water demand) and deeper root growth is encouraged. Taller grass also shades the soil, which lowers evaporation and reduces weed seed germination.
Finally, think twice before running water. Indoors, for example, flush the toilet only when necessary. Turn off the tap while brushing your teeth. Capture water in a bucket or a large pot while the shower or the dishwater is warming up and use it to water garden plants. Using a broom instead of the hose to clean a driveway can save hundreds of gallons of water. Leaving the hose running while washing a car can waste 150 gallons of water; instead, re-fill a bucket with water as needed, and turn off the hose. It's often just a matter of common sense.
Geisel, Pamela M. "Pub. 8036 Water Conservation Tips for the Home Lawn and Garden." Anrcatalog.ucdavis.edu. UCANR, n.d. Web. http://anrcatalog.ucdavis.edu/pdf/8036.pdf
"Water Conservation in Your Garden & Landscape Checklist." Colusa County Farm Bureau. UCCE, n.d. Web. http://cecolusa.ucanr.edu/files/65442.pdf
Kim, Dohee. "Questions and Answers about Water Conservation." UC Cooperative Extension Connection. UCANR, n.d. Web. http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=5356
Water Conservation Suggestions for Your Home Vegetable Garden." UCCE Master Gardeners of Trinity County, n.d. Web. http://cetrinity.ucanr.edu/files/180197.pdf