Posts Tagged: Drought
This week much of California is under a heat advisory or excessive heat warning, with high temperatures estimated to range from 90 to 108 degrees. Many home gardeners are wondering how they can help their plants, trees, or shrubs survive the intense...
[From the Spring issue of the UC IPM Retail Nursery & Garden Center News] Most disorders impacting landscape trees result from abiotic (non-living) disorders rather than attacks from biotic (living) pests like plant pathogens, insects, and...
This time of year, deciduous trees go dormant, and evergreen trees such as pine are more visible in the landscape. Pine trees, like other plants, can suffer from attack by pests, whether on your property or in our forested areas in California. Pine...
Can you help fight the California drought by consuming only foods and beverages that require minimal water to produce?
Daniel Sumner, director of the UC Agricultural Issues Center at UC Davis, and research assistant Nina M. Anderson mine the details of this issue to help us all better understand just what impact our food choices can have on conserving California's precious water.
To begin with, not all water drops are equal because not all water uses impact California's drought, the researchers explain.
So just what water does qualify as California drought-relevant water? You can definitely count surface water and groundwater used for agricultural irrigation as well as water used for urban purposes, including industrial, commercial and household uses.
And here are a few examples of what water is not relevant to California's drought:
-- Water used in another state to produce young livestock that are later shipped to California for food production; and
-- Rain that falls on un-irrigated California pastureland. (Studies show that non-irrigated, grazed pastures actually release more water into streams and rivers than do un-grazed pastures, the researchers say.)
In short, California's drought-relevant water includes all irrigation water, but excludes rainfall on non-irrigated California pastures as well as any water that actually came from out-of-state sources and wound up in livestock feeds or young livestock eventually imported by California farmers and ranchers.
Also, the amount of water that soaks back into the ground following crop irrigation doesn't count – and that amount can be quantified for each crop.
Comparing water use for various foods
I think you're getting the picture; this water-for-food analysis is complicated. For this paper, the researchers examined five plant-based and two animal-based food products: almonds, wine, tomatoes, broccoli, lettuce, milk and beef steak.
In teasing out the accurate amount of water that can be attributed to each food, the researchers first calculated how much water must be applied to grow a serving of each crop or animal product. Then they backed off the amount of water that is not California drought-relevant water, arriving at a second figure for the amount of drought-relevant water used for each food.
They provide a terrific graph (Fig. 3) that makes this all quite clear, comparing total applied water with California drought-relevant water used for the seven food products.
Milk and steak top the chart in total water use, with 1 cup of milk requiring 68 total gallons of water and a 3-ounce steak requiring 883.5 total gallons of water.
But when only California drought-relevant water is considered, one cup of milk is shown to be using 22 gallons of water and that 3-oz steak is using just 10.5 gallons of water. (Remember, to accurately assess California drought-water usage, we had to back off rainwater on non-irrigated pastures and water applied out of state to raise young livestock or feed that eventually would be imported by California producers.)
“Remarkably, a serving of steak uses much less water than a serving of almonds, or a glass of milk or wine, and about the same as a serving of broccoli or stewed tomatoes,” write Sumner and Anderson.
Still skeptical? Check out their paper in the January-February issue of the “Update” newsletter of the Giannini Foundation of Agricultural Economics at http://bit.ly/1XKZxxC.
Street-side stormwater facilities are turning runoff once seen as a nuisance into a resource. Also known as bioretention areas, rain gardens, and bioswales, these small stormwater facilities provide a decentralized approach to alleviating peak stormwater runoff and subsequent flood damages. These are particularly critical functions in cities like San Francisco where the storm and sanitary sewer systems are combined because they help managers to prevent dreaded “combined sewer overflow” events. As a bonus, stormwater facilities have also proved useful in promoting groundwater recharge and filtering pollutants as water percolates through soils.
While street-side facilities are effective in helping to manage stormwater runoff, how the trees that are often planted in them fare is not as well-understood. In theory, trees in stormwater facilities serve many purposes, including stabilizing soils and improving water infiltration and uptake of nutrients and pollutants. They also provide the same well-known benefits as other urban trees: shade, carbon sequestration and storage, air pollution reduction, and aesthetic improvement.
The challenge is that trees have been expected to survive and even thrive in stormwater facilities, but there is little research available to guide the process. This is particularly true for climates like California's with distinct wet and dry seasons, where irrigation might be needed to keep trees alive during the summer. This is where Igor Lacan, a University of California cooperative extension advisor, comes in. He has spent much of the last several months outfitting locations in northern California with sensors that will help him to develop best practices for managing trees in street-side stormwater facilities.
Lacan says that tree survival in stormwater facilities likely depends on at least three factors: how long tree roots stay submerged during a storm event, the intensity of California's summer dry period, and the quality of the soil used. He notes that there are likely multiple trade-offs between these factors. He says, for example, that “a permeable sandy soil might drain well during rainy winter months, but would not help trees retain water during the hot, dry summer months. At the same time, a clay soil better at retaining moisture could become waterlogged during a large storm event.”
To better understand these trade-offs, Lacan first has to locate the facilities – a more challenging task he originally imagined. Many easily blend into the surrounding urban landscape, and are incredibly diverse in their design. “No two are alike,” says Lacan. He then identifies the trees, evaluates their size and condition, and installs soil moisture sensors. One of the biggest concerns about the research is how well the sensors – buried in the soils to help escape attention from passersby – will survive periodic immersion in rain water.
Lacan started the project after some casual comments from arborists who expressed reluctance about planting trees in stormwater facilities. He says the concern has now spread to local city foresters as well -- they worry about excessive tree mortality. At this point, he is excited to reassure managers that the “verdict is not yet in” and enlist them as study partners, with the hopes of optimizing tree survival.
After years spent researching stormwater facilities in rainy Portland, Oregon, he says that one interaction while doing field work epitomizes the need for more research on tree survival in California's Mediterranean climate. A man walking by a bioswale as the researcher dug around installing a sensor was asked by his toddler what was going on – the father casually explained that Lacan was fixing the irrigation system. “That one made me smile,” says Lacan. “It is of course natural to think that our California bioswales would come with an irrigation system.”
Post also available in Spanish: Estudian cómo sobreviven los árboles en zonas de retención de agua de lluvia
This research was supported in part through a grant to Principal Investigator Igor Lacan with the University of California, Division of Agriculture and Natural Resources from the California Institute for Water Resources in the University of California's Division of Agriculture and Natural Resources.