From Stanford: Future Water Resources
California isn't running out of water,” says Richard Luthy. “It's running out of cheap water. But the state can't keep doing what it's been doing for the past 100 years.”
Luthy knows. As a professor of civil and environmental engineering at Stanford, as well as director of a National Science Foundation center to re-invent urban water supply (known as ReNUWIt), he has spent decades studying the state's metropolitan areas.
In a new journal article, he argues that California cities can no longer rely on their three traditional water-coping strategies: over-drafting groundwater, depleting streams and importing water from far away. His analysis focuses on several strategies that, taken together, can help cities provide for their growing population with prudent public policies and investments:
Conservation is cheap, says Luthy. Eliminating lawns or taking shorter showers are behavioral changes that don't require new spending on infrastructure.
Some cities have already made great strides. Los Angeles, for example, added 1.1 million residents between 1990 and 2010, but kept total water consumption flat through conservation, as homeowners and builders install things like low-flow toilets and high-efficiency washing machines. Similarly, two dozen San Francisco Bay Area cities cut total consumption by about 23% between 2004 and 2016 even as their populations grew by 10%.
But conservation isn't enough to match population growth. Although Southern California water officials recently predicted that by 2040 expanded conservation efforts should save enough water to supply about 2.3 million new residents, officials also expect population to grow by 3.1 million by then.
California can do more, Luthy says. About 10% of water distributed in urban areas is lost to leaks. Since the last drought, California utilities have conducted water loss audits to curb such waste. “Conservation is essential to help meet urban water demand, but we also need other measures to increase supply,” Luthy says.
The reuse of non-potable water for irrigation or other purposes has a long history in California. More than a century ago, cities like Fresno were reusing sewage water to irrigate surrounding farms. In the 1980s, the Irvine Ranch Water District built a dual-distribution system that now delivers 25 million gallons per day of purified non-potable water to farms and businesses.
Cities could do the same today, but to recycle non-potable water, planners would have to build pipe networks to separate the non-potable water from the drinking water, at a cost of between $1 million to $10 million per mile.
Most short-distance opportunities have already been implemented. That still leaves new opportunities for smaller, decentralized projects where wastewater is generated and needed. The Salesforce Tower in San Francisco, for example, will soon be recycling about 30,000 gallons of wastewater a day for all purposes except drinking. Distributed non-potable reuse is also catching on with tech campuses in Silicon Valley.
The real future, says Luthy, is potable reuse – making recycled water pure enough to drink.
Potable reuse is a process that begins by purifying wastewater in treatment plants and then feeding this cleansed water back into reservoirs or underground aquifers. Water utilities then mix the recycled water with new, fresh water to meet the standards for potability.
A number of counties and municipalities are already making advances in this area.
Orange County Water District has been a leader in potable reuse and the practice of “full advanced treatment” since 2004, and many other cities have plans to recycle at least some highly treated wastewater for drinking. For example, Los Angeles is currently considering an ambitious project to recycle virtually all its wastewater to eventually make it available for potable reuse by 2035 at a cost of $8 billion. A comparable project for the San Francisco Bay Area would involve expensive upfront infrastructure, but those initial outlays could ultimately be worth it as the supply of water imported from the Sierra decreases due to climate impacts and ecosystem needs, and the cost climbs, as expected, by 60% over the next decade.
Billions of gallons of storm water simply pour into the ocean annually. That needs to change, Luthy says. California's coastal cities were historically engineered to flush out storm water to reduce flooding, but today cities want to capture as much as possible and put it to use. Los Angeles already gets 10% of its water from storm water runoff, and hopes to more than double that by 2035. Like potable reuse, however, storm water capture often requires big investments in pipes, storage sites and treatment facilities. The capital costs of such infrastructure vary widely, depending on local conditions. But the median project cost is often cheaper than costs to import water in the future, even assuming it will be available, Luthy says.
The ocean has virtually limitless water, and some communities are taking advantage of desalination to meet their needs. San Diego Water Authority's desalination system, built at a cost of $1 billion, already delivers 50 million gallons per day – about 8% of its needs. But desalinating seawater is costly and energy intensive, and can harm marine life, which is why Luthy says other communities are desalinating brackish water from estuaries where rivers meet the sea. (Brackish water has a lower salt content than ocean water, which makes it easier and cheaper to treat.)
Alameda County already produces about 10 million gallons of drinking water per day by desalinating brackish groundwater in Newark. A partnership of five agencies in the Bay Area is considering a $200 million plant that could desalinate about 20 million gallons of brackish water per day from the North Bay estuaries for about the same cost per gallon as consumers currently pay to import water from the Hetch Hetchy Reservoir.
It's an ancient story that climate change makes increasingly common: too much rain and snow in wet years, and not enough in dry ones. One way to deal with these extremes is to “bank” extra water from wet years in underground aquifers. This is possible because the state's major metropolitan areas are linked by the 400-mile California Aqueduct. Cities in the north can “deposit” water in wet years by not taking withdrawals from the aqueduct and allowing that water to be pumped out and stored instead in Kern County, heart of the agricultural region near the end of the aqueduct. In dry years, northern cities could make “withdrawals” by taking extra water from the aqueduct and rely on the water stored in Kern County to be pumped back into the aqueduct, to make sure that enough water continues to flow to cities in Southern California.
“No single one of these measures will work in isolation, but if we plan wisely now, urban water will be available when we need it,” Luthy says./h2>/h2>/h2>/h2>/h2>/h2>
What Can Happen With Too Much Rain?
Rain is wonderful stuff. If it comes and washes the accumulated salts of the last several years out of the root zones of citrus and avocado, that's a good thing. But what happens if there is a little too much of the good stuff? In the winter of 2005, Venture got over 40” of rain, which is 200% of what is normal. The last time big rains occurred prior to that was in the winter of 1997-98. That year the rains were evenly spaced on almost a weekly basis through the winter and into the late spring and over 50" fell. That year we had major problems with both citrus and avocados collapsing from asphyxiation. The same occurred in 2005, but not so pronounced.
This April we have had a lot more rain than we normally see and in some young trees with poorly developed root systems, we have seen some collapse from asphyxiation. Avocados tend to be more susceptible than citrus, and some rootstocks more than others.
Asphyxiation is a physiological problem that may affect certain branches, whole limbs or the entire tree. Leaves wilt and may fall, the fruit withers and drops and the branches die back to a greater or lesser extent. The condition develops so rapidly that it may be regarded as a form of collapse. Usually, the larger stems and branches remain alive, and after a time, vigorous new growth is put out so that the tree tends to recover. Young trees can be harder hit, but sunburn damage from lack of leaves may be more of a problem.
Asphyxiation is related to the air and water conditions of the soil. The trouble appears mainly in fine-textured or shallow soils with impervious sub-soils. In 1997-98, this even occurred on slopes with normally good drainage because the rains were so frequent. When such soils are over-irrigated or wetted by rains, the water displaces the soil oxygen. The smaller roots die when deprived of oxygen. When the stress of water shortage develops, the impaired roots are unable to supply water to the leaves rapidly enough and the tree collapses. The condition is accentuated when rainy weather is followed by winds or warm conditions. These are exactly the conditions we saw in the last weeks of April and beginning of May - wet weather and then 90 degree heat. Boom. hence some of the problems in young orchards on heavier soils.
It doesn't take standing water to have asphyxiation occur.
Canopy treatment in less severe instances of asphyxiation consists of cutting back the dead branches to live wood. If leaf drop has been excessive, the tree should be whitewashed to prevent sunburn. Fruit, if mature should be harvested as soon as possible to prevent loss. In the case of young trees, less than two years of age, recovery sometimes does not occur, and replanting should be considered if vigorous regrowth does not occur by July. As soon as defoliation is evident, whitewashing should be done to protect them to give them a chance for recovery.
Asphyxiation can be reduced by proper planting and grading. If an impervious layer is identified, it should be ripped prior to planting. The field should be graded so that water has somewhere to run off the field during high rainfall years. Heavier soils might require planting on berms or mounds so that the crown roots have a better chance of being aerated.
Hindsight is always great. Post-plant, if an impervious layer can be identified and is shallow enough to break through, ripping alongside the tree or drilling 4-6 inch post holes at the corners of the tree canopy can improve drainage. It is important that the ripper blade or auger gets below the impervious layer for this technique to be effective. If there is a thick layer of mulch reducing soil evaporation, pulling it back to allow the sun to help dry it out faster will help. It's not a lot of work with small trees, but big time work if it's big trees with thick mulch.
Asphyxiated tree that has been whitewashed
The MOST Cited irrigation articles for 2018-19 in the journal Irrigation Science was just announced. Check them out. One that interested me was conducted in Southern California and looked at the costs of recycled water use in nurseries. The cost aspect makes this water source possible if it is subsidized.
In the U.S., container plant growers use high-quality water sources which can be expensive. The use of recycled irrigation runoff water could save growers money. The objective of this study was to compare the cost of recycled irrigation water with the cost of untreated municipal water at a nursery in Southern California over multiple years. Water cost for municipal (Western) supplied water ranged from $2.26 to $2.91 per 1000 gallons (3785 L). Water capturing and recycling system construction and infrastructure costs accounted for a large portion of recycled water cost. However, water provider rebates and a Natural Resource Conservation Service (NRCS) grant reduced total and per volume recycled water costs. Without considering rebates from water providers and a NRCS grant, the cost of recycled water was between $0.92 and $1.21 per 1000 gallons (3785 L). With consideration of rebates and the grant, the cost of recycled water ranged between $0.43 and $0.53 per 1000 gallons (3785 L). Thus, recycled water is a viable alternative to many high cost water sources and public funds facilitate adoption of recycled water for irrigation by containerized plant growers.
I just came across a wonderful summary of the different methods that can be used to schedule irrigations based on plant sensors. In th past this is has been labor intensive and not easily adapted to commercial agriculture. This review covers some of those problems and how they have or not been overcome by new technologies. Of course, plant-based techniques are the not the only way to schedule and may only be part of the variety of methods used, such as soil-based ones like tensiometers; or weather-based ones, like ET. A shovel and just looking at trees helps too.
Plant-Based Methods for Irrigation Scheduling
of Woody Crops
The increasing world population and expected climate scenarios impel the agricultural sector towards a more efficient use of water. The scientific community is responding to that challenge by developing a variety of methods and technologies to increase crop water productivity. Precision irrigation is intended to achieve that purpose, through the wise choice of the irrigation system, the irrigation strategy, the method to schedule irrigation, and the production target. In this review, the relevance of precision irrigation for a rational use of water in agriculture, and methods related to the use of plant-based measurements for both the assessment of plant water stress and irrigation scheduling, are considered. These include non-automated, conventional methods based on manual records of plant water status and gas exchange, and automated methods where the related variable is recorded continuously and automatically. Thus, the use of methodologies based on the Scholander chamber and portable gas analysers, as well as those of systems for measuring sap flow, stem diameter variation and leaf turgor pressure, are reviewed. Other methods less used but with a potential to improve irrigation are also considered. These include those based on measurements related to the stem and leaf water content, and to changes in electrical potential within the plant. The use of measurements related to canopy temperature, both for direct assessment of water stress and for defining zones with different irrigation requirements, is also addressed. Finally, the importance of choosing the production target wisely, and the need for economic analyses to obtain maximum benefit of the technology related to precision irrigation, are outlined.
- Author: Linda Chalker-Scott
- Author: Jim Downer
Washington State University and UCCE - Ventura County, respectively
Horticultural myths, found extensively in print and online resources, are passed along by uninformed gardeners, nursery staff, and landscape professionals. Occasionally myths are so compelling that they make their way into Extension publications, used by Master Gardeners as educational resources. In this article we deconstruct seven widespread gardening myths by way of reviewing research-based literature. We also provide scientifically sound alternatives to these gardening practices and products. Our hope is to arm Extension educators with the educational resources necessary to battle misinformation that ranges from the merely useless to that which is actively damaging to soils, plants, and the surrounding environment.
Home gardeners and landscape professionals are a rapidly growing audience for extension educators as they seek science-based information to support their activities. However, many are not familiar with current research and cannot assess whether the information they find in print, on the internet, or through social media is accurate. In addition, some products and practices are meant for agricultural production, not for maintaining home gardens and landscapes. The combination of misinformation and misapplied information means that this audience risks damaging their plants and soils through overuse of fertilizers, misuse of pesticides, and poor management practices.
The field of urban horticulture, including arboriculture, is expanding with new insights about plants and soils in residential and public landscapes. However, there are few Extension educators who have an academic background in environmental horticulture and may be as confused as the public about what constitutes sound, science-based recommendations.
The authors of this article are state Cooperative Extension educators and researchers with many years of experience in translating science for use by home gardeners and landscape professionals. Our goal is to assist other Extension educators by providing reliable information for them to share with the gardening and landscaping public.
The purposes of this literature review article are:
- to identify some common beliefs homeowners and landscape professionals have about managing landscape plants and soils;
- to provide a brief, science-based explanation on why these beliefs are not accurate;
- to provide links to published, peer-reviewed information that supports the explanation and can be distributed to clientele; and
- to suggest strategies based on current and relevant applied plant and soil sciences for managed landscapes.
And here is the article:
Garden Myth Busting for Extension Educators: Reviewing the literture on Landscape Trees