Water

water

"Water is the driving force of all nature."
- Leonardo di Vinci

introduction

Water is a vital, life-giving force in the garden that should not be overlooked when planning and caring for your space. Learning how water flows across your property, how it is used by plants, and how it can be conserved and saved for periods of drought are all pieces of knowledge that will assist in creating a water-wise garden.

How Plants Use Water

Water typically constitutes 85% to 90% of the weight of a plant, and supports essential life processes that occur within plant cells. It plays an important role in transporting dissolved minerals from the soil and sugars from the leaves to all cells in the plant, maintains cell turgor, or rigidity, and indirectly regulates growth. The importance of water to plant life can really not be understated, no matter how drought-tolerant the plant is. Water enters the soil through precipitation (rain, snow, and the like) or irrigation, and then enters plants alongside nutrients drawn from the soil. After the plant has used what water it needs, the rest is released into the atmosphere in the form of water vapor. This process is called transpiration.

A second way that garden water is lost to the atmosphere is by evaporation. Evaporation is the process by which liquid water turns into gaseous water (water vapor), and is then taken up into the atmosphere. Evaporation happens when heat energy breaks apart the molecules that hold water together. Most of the water in our atmosphere comes from water that has evaporated from bodies of water, such as oceans, lakes, and rivers. The rest of the moisture in the air comes from plant transpiration (and a little bit is due to sublimation - water transforming from its solid state (ice) directly into a gaseous state. In the garden, evaporation occurs when water in the soil heats to a temperature at which it is then pulled from the soil and lost to the atmosphere. The total amount of water lost within a garden is called evapotranspiration, or ET (evaporation and transpiration combined).

Quick Question: How does water travel from the roots to the top of a plant?
It seems remarkable that water can travel against gravity up through the interior of a plant, sometimes 50 to 100 feet or more. Water molecules have strong bonds within themselves and with other neighboring water molecules. This produces a great tensile strength. Water molecules form a chain up the interior of a plant through the system of channels of xylem that exist within stems and leaves. As the molecules move towards the exits (stoma) of leaves, they pull their neighboring water molecule with them, and so on and so forth along the water chain down to the roots. As water is lost through evaporation through stomata, more water is pulled from the other end of the water molecule chain into the plant.

Evapotranspiration (ET) rates vary among plant species, and is driven by the sun and other environmental factors such as heat, humidity, and wind speed. It is expressed in units of depth (either inches or millimeters) or volume (either gallons or liters) per length of time (days, weeks, months, or years). The rate of evapotranspiration when graphed creates a bell curve through the year, with higher rates in the middle of summer and lower rates in the middle of winter. The chart shown here illustrates this trend, showing monthly average ET for various zones in California.

ET rates also vary depending on soil types, with sandy soil holding on to 1/4 to 1/6 of the amount that clay soil can hold. A plant in clay soil requires just as much water as the same plant growing in sandy soil, but because the soils hold water differently, they will need to be watered differently. Because there are so many factors at play in estimating ET rates, location-specific data has been collected and published for quick reference. To use this data, begin by finding your ET zone on the map of California. Then, find that zone on the ET average rate chart.

the way of water

The initial entry of water into soil is called infiltration. The infiltration rate represents how quickly water enters into soil, expressed in inches or centimeters per hour. It is determined by soil qualities like structure and type, the type of cover on the surface of the soil, the slope of the land itself, the current water saturation of the soil, and water quality. How readily water moves downward through the soil profile is referred to as percolation or permeability. For example, the same volume of water will travel downward through soil farther in sandy soil than it would in clay or loam soil. Good infiltration and permeability are very important factors in the garden because they ensure that required water reaches the root zone of plants, that runoff and erosion are mitigated, and that air can move efficiently into soil pore space.

When the application rate of an irrigation system is greater than the infiltration rate of the garden soil (or if the soil is already fully saturated when the irrigation is applied), runoff occurs. Runoff is an issue for a few reasons. It is wasted water that will not be used by plants, and it can cause soil erosion. Additional water can also be lost underneath the root zone, where it is not accessible by plants; a process called deep percolation. If there is no slope to the garden, water can also form pools of standing water on a property, and if this occurs where plants are situated, they can drown.

The drainage situation on a property can be measured using a simple test. First, dig a hole 12-18 inches deep and fill the hole with water. If your soil is dry to start with, allow the water to drain out of the hole completely, and then fill it again. Monitor how long the water takes to drain out of the hole. If all water is gone from the hole within a few hours, drainage in the garden is considered adequate for most plants. If the hole takes 24 hours or more to drain, drainage is slow and your plants may be suffering as a result. In this latter situation, soil will need amending with organic matter in order to create a welcoming environment for plant roots. Slow drainage in garden soil can be caused by the soil being clay-rich, restrictive horizons or claypans, dense or compacted layers, abrupt changes in soil texture in a short distance, or a high groundwater table. For information on how to amend soil in these situations, see the Soil module.

IRrigation systems

Irrigation (also referred to as watering) refers to the artificial application of water to soil through a variety of systems. There are many ways to apply water to a landscape, including surface irrigation (or gravity irrigation), sprinkler irrigation, micro irrigation, drip irrigation, and sub-irrigation. Irrigation has been a vital aspect of agriculture and gardening for the past 5,000 years, and has been developed by many cultures around the world.

The History of Irrigation

The earliest archaeological evidence of irrigation in farming dates back to 6,000 BC in the Jordan Valley. Around this time, agriculturalists in Egypt were also creating formal irrigation systems to provide additional water to crops to support a growing population. The earliest pictoral representation of irrigation is found in Egypt dating back to 3,100 B.C. From these areas, the use of irrigation systems spread through Persia, the Middle East, and along the Mediterranean Sea. Irrigation systems also appeared around this time in Pakistan, India, China, and in the Inca, Maya and Aztec civilizations. Irrigation was first introduced into the United States in what is now Arizona, in the 13th and 14th centuries. Some of these irrigation systems stood the test of time, but sadly others caused irreparable damage to the landscape and surrounding ecology. In areas where irrigation systems proved successful, additional water-centric engineering projects were created, including dams, canals, dikes, and water storage facilities. During the 20th century, the amount of irrigated land doubled; at this time, about 18 percent of the world's land area is formally irrigated, and these areas feed approximately 80 percent of the world's population.

Modern Irrigation Systems

There are many techniques that have been developed over the history of human civilization to irrigate landscapes. In this section, we will describe how water is used in residential landscapes and for kitchen gardens. Disregarding which irrigation system is used, there are a few overarching rules to making sure it is functioning correctly and in the right capacity. Correctly installing and maintaining your watering system is critical for the long-term success of the surrounding ecosystem, the health and development of your plantings, and for conserving water. The following tips will ensure that an irrigation system performs efficiently.

Irrigation lines that feed sprinkler heads or drip emitters should be placed perpendicular to slopes rather than parallel to them. Spray heads should also be placed perpendicular to slopes. This will ensure that water does not simply roll down the hill on the surface of the soil instead of being absorbed into the root zone of irrigated plants.

The irrigation system should be designed in a way so that each valve or station supplies water to an area of plants that have similar water needs. Grouping plants of similar water needs will reduce wasted water, and ensure that plants are getting the moisture they need.

Install heads and emitters of the same make on each irrigation valve or station and replace them with like products when repairs are required. Place the spray heads so that their water output fully overlaps the output of adjacent heads in the system.

Automated Sprinkler Systems and Weather-Sensing Controllers
These state-of-the-art watering systems are widely used by home gardeners across California. These automatic systems provide multiple irrigation programs and cycles, can adjust in response to weather and climate conditions, and some can even interface to your computer or smartphone. They can be used with many different water delivery methods, including drip, sprinklers, and hoses. Specialized weather-sensing controllers automatically adjust waterings depending on weather conditions with the goal of conserving water. These systems usually require some tweaking by experienced horticulturalists to work at peak efficiency.

Hose-End Sprinklers
Using hose-end sprinklers is a common practice among many Californians who use them to water lawn areas and other plantings. To cover large swaths of land, multiple sprinklers can be used or a single sprinkler can be moved periodically during the watering cycle. Using this type of irrigation requires some ongoing upkeep and monitoring, including:

Checking for leaks between the faucet and hose. Sometimes, new rubber washers may be needed to replace degraded ones. These washers are inexpensive and easy to install.
Placing the sprinkler head in a central location surrounded by the plants intended to be watered. Avoid placing these sprinklers near sidewalks, driveways, and structures unless their flow can be directed so that water is not wasted on these hard surfaces.
Using sprinklers responsibly so that their spray does not come into contact with tree trunks, and so that the output is directed towards their intended targets.
Using a separate type of irrigation for trees and established shrubs that allows for a slower, deeper soak.

Furrow Irrigation
This technique is best used for fruit and vegetable plantings, and does well in raised beds. This technique is valued because it does not wet the foliage of plants, decreasing the risk of fungal diseases.

Drip Irrigation
This popular type of irrigation rests on the fact that it is best to frequently and slowly irrigate landscapes. Emitters in this system are spaced along delivery lines 1/2 inch in diameter. Basic drip systems have three parts: a flow control, pressure regulator and filter; a system of flexible plastic hose, and emitters. Drip irrigation waters a limited area of soil, a portion of the plant's root systems, reduces water waste in the area between plants and minimizes water evaporation, and prevents germination of weed seeds in between plants. Drip irrigation systems work well for many areas of the garden and for a wide variety of plants, including vegetables, ornamental and fruit trees, shrubs, vines, and containers. Soaker hoses are a related form of irrigation, but they do not provide as uniform waterings as does a true drip system. Drip irrigation systems have many benefits. Water gets more accurately and efficiently placed in the root zone. Runoff is minimized due to the slow speed at which water is dispersed. The foliage of watered plants remains dry, reducing disease. The space between plantings also remains dry, giving gardeners more space to work in the garden. There are some issues with this type of system, including the initial cost required in labor and materials, as well as the ongoing maintenance required to keep the system in working order. Otherwise, drip irrigation is ideal for most garden water needs. For more information on setting up a drip irrigation system, visit the page linked here:

Drip Tips

Basin Irrigation
For tree or shrub plantings, basin irrigation is recommended. This method requires building up a doughnut-shaped basin around the base of the plant with a berm under the drip irrigation line and a second berm closer in to the trunk to prevent water from touching the trunk itself.

irrigation tips and best practices

There are many ways in which irrigation systems can be managed to best maintain healthy landscapes and gardens and save as much water as possible. The following concepts and guidelines are some of the best ways to ensure that as little water as possible is wasted in the garden.

Create Hydrozones
Plants with similar water needs should be grouped together in irrigation zones. An irrigation zone refers to an area watered by the same valve and controller station. Grouping plants in this way allows the correct amount of water to be applied to plants at the correct time, and leads to healthier planting beds overall. Planting beds with plants that have differing water needs will need to be manually watered to ensure that each plant is getting adequate water down to its root zone.

Apply the Correct Amount of Water
In general, overwatering plants is much more common than underwatering plants. Research shows that many plants are overirrigated by 20-40 percent or more. Even on hot summer days, many plants are overwatered. This is partially due to the fact that California soils are clay-heavy, and hold more water and dry out more slowly, making them more susceptible to being overwatered. To judge whether a garden is being overwatered, a simple test can be done. The main piece of information needed to determine how much water a landscape needs

If plants are watered manually with a hose, turn it on at the force that is commonly used for watering, and time how long it takes in minutes to fill a one gallon container. This will be the rate of water application for this method. If a drip system is used, they are usually designed to deliver between 1 and 3 gallons of water per hour. A gallon of water adds 1.6 inches of water over a square foot of dry land and wets the area to a depth of 1.5 inches (though this integer depends on soil texture and existing soil water content when the water is added). Another way to look at it is that 0.62 gallons of water applies an inch of water to square foot of garden soil. A handy equation to use to estimate water application rates is:

inches of water =

gallons

(sq. ft. of planting area x 0.62)

The right amount of water needed for your landscape and garden plantings will depend on the ET rates in your area (which depends on your specific microclimate). There are eleven established zones in California that have distinct average ET rates depending on the month of the year. This data is contained in the table found in the 'How Plants Use Water' section above.

Water Plants Deeply and Infrequently
The soil should be wet to just beyond the root zone of established plantings, and the soil should be allowed to dry out a bit in between irrigations. By engaging in this practice, root rot diseases are discouraged, and a water reservoir is established, providing adequate water for all plants in the area when they need it. In areas where there is little rainfall, such as deserts, extra water must be applied occasionally to leach salts out of the root zone so that it does not harm plant roots. If using a drip irrigation system, schedule with short intervals between irrigations in order to keep soil adequately wet. Knowing the root depth of your plants is a key piece of information needed when determining how deep you need water to percolate into the soil. In general, the following plant categories will have different rooting depths:

Leafy Vegetables and Annual Bedding Plants
Roots from 6 inches to 1 foot down.

Cool-Season Turfgrass and Flowering Perennials
Roots from 6 inches to 1.5 feet down.

Shrubs, Trees, Groundcovers, Vines, Warm-Season Turfgrass, and Non-Leafy Vegetable Crops
Roots from 1 to 6 feet down.

Although plants vary in their rooting depths by species and variety, they can be classified into these three groups generally. There are many limiting factors that can affect a plant's genetic rooting potential, so it is best to sample soil around a given plant to more accurately estimate the exact depth of its root system.

Water Early in the Morning
In the early morning, conditions are perfect for applying water to a landscape. There is generally less wind and conditions are cooler, reducing evaporative water loss and disruption of sprinkler pattern uniformity. Because watering early in the morning usually means watering when no one is around, it is important to check irrigation systems regularly for broken or inoperative components and leaks that may otherwise go undetected. The exception to this early watering guideline is with drip systems, whose water is released in such a slow, direct manner to the soil surface. These systems can be efficiently operated at any time of the day, without much reason to worry about water loss through evaporation.

Avoid Deep Percolation and Runoff
Overwatering can lead to both deep percolation and runoff, both of which are wastes of garden irrigation water. Deep percolation refers to significant water movement below the root zone of plants. This water is not available for uptake, and is therefore wasted. Applying water for shorter periods of time can substantially reduce this issue. Due to the structure of some soils, there is more of a problem with runoff than with deep percolation. Runoff occurs when soil infiltration is poor; the water simply hits the soil surface and 'runs off'. Applying water at lower rates, for example using a drip system instead of hose watering, can greatly improve runoff issues in the garden. Cycling water can also reduce runoff. This process involves splitting waterings into multiple irrigations rather than one, spaced several minutes to an hour apart while the soil is still moist but able to take in more water.

If issues with runoff are present in a garden, a great way to establish a healthy watering schedule is to apply water every hour for 5-10 minutes or until runoff begins. Repeat this cycle as many times as it takes to wet the soil to the depth of the surrounding plants' root systems. Although this will take some time investment to begin with, after an ideal irrigation schedule is built, it can be followed with ease and tweaked for seasonal changes. Runoff can also be avoided by not using high-output fixed-head sprinklers, which usually apply water more quickly than it can be absorbed into the soil, especially in sloped areas of the garden. Choosing rotating spray or stream heads that apply water very slowly. Although these types of irrigation need to be run for much longer to apply the same amount of water, the water applied is actually able to be used by plants. In sloped areas, drip irrigation is highly recommended, as well as low-volume micro- and mini-sprinklers.

Apply Water Uniformly
Even applications of water over a planted area reduces water loss and improves the health of plants. This tip is especially useful to consider when applying irrigation to a lawn area. When sprinkler systems are not balanced properly, some areas of a lawn will receive much more water than others, as illustrated in the photograph shown. Brown, drought-stressed grass areas will develop, inviting weeds to take hold and creating a less-than pleasing look. Many homeowners will simply run their sprinkler systems for longer periods of time in the hope that the water will simply just 'spread out' and cover the entire lawn, but instead can cause overwatering problems as well as drought problems across the entire lawn.

A homeowner's sprinkler system that is applying water half as evenly as their neighbors' will require about twice as much water to ensure that all areas of the lawn are properly saturated. Over the course of a summer season, this can lead to both higher water bills as well as a high amount of wasted water due to runoff. Regularly conducting can tests can ensure that uniformity problems are detected, and possible hardware issues can be corrected.

Maintain and Adjust Irrigation Controllers and Systems
When seasons change, the ET rates and water needs of plants change, as well. Lower amounts of water are required over the late fall, winter months, and early springtime and more is required in summertime. Adjusting irrigation according to these seasonal changes can decrease water use over the year by up to 50%, and also can enhance plant health. Areas with established deciduous trees and shrubs need hardly any water over the winter months, as long as rainfall is near normal. Many landscape trees, shrubs, ground covers, and lawns are overwatered during fall and winter because automatic irrigation systems are not adjusted.

Checking irrigation systems regularly for physical and operational problems is key to preventing water waste in the garden. A simple way to check an irrigation system is to turn it on and walk around the yard, taking note of anything that looks out of the ordinary. Correcting issues in irrigation systems can reduce water waste by between 20% and 50% and can also improve plant health.

Apply Mulch
Planting beds benefit greatly from a layer of mulch applied 2-4 inches deep on the surface of the soil. This is one of the most beneficial things a homeowner can do for their garden; the use of mulch can help insulate soil from drastic changes in temperature, suppress weed growth, provide slowly-leaching nutrients (if an organic mulch is used), and, most importantly for this discussion, reduce water evaporation from the soil. Intervals between irrigations can be lengthened with the use of mulch; yards using mulch will require less frequent waterings than those with bare soil. When applying mulch, it should be kept away from plant trunks and stems by several inches, and extend outward toward the drip line. Soil under the mulch layer should be checked periodically to ensure that water is penetrating the soil through the mulch. Drip lines should be installed underneath the mulch layer.

Amend High Sand or Clay-Content Soil
Soil high in clay content tends to repel water, leading to issues with runoff and poor percolation. Amending this type of soil with organic matter will improve structure, and therefore allow more water to reach the root zone. Sandy soils have issues with deep percolation, where water passes right through the root zone and is not available to plants. Sandy soil amended with organic matter will hold more water and require less frequent irrigation.

situation-specific Water management strategies

Because there are so many variables that affect how water flows across a property and is used by plants in the garden, it is a good idea to create different irrigation practices for each distinct area. The following tips and considerations will assist in planning out or tweaking an already existing irrigation plan depending on the types of plantings present in the garden.

Annuals and Perennials
Newly installed beds of annual and perennial plants require frequent and uniform supplies of water while their roots are getting established in the soil. It may be necessary to apply water one or more times during warm or windy weather. Once established, irrigations can be reduced. For mature beds, water can be applied every two to three days at about 75% to 100% of ET. During cool weather, irrigation can be applied 1-2 times per week. Enough water to rewet the root system should be applied at each planting.

Vegetables
Veggies require on average about 75% to 100% of ET and must be watered regularly throughout their growth cycle to produce well. There are differences in watering requirements depending on the time of the year they are grown, the size of the plant, and the variations in length of the plant's growing seasons. Irrigate vegetable seeds, seedlings, and recent transplants frequently as they are getting established to promote uniform, healthy growth and optimum yields. Maintaining a uniform soil moisture is also important for established plants. Shallow-rooted crops will need more frequent irrigation than deep-rooted ones. Adding a layer of mulch around vegetable plantings will help maintain even soil moisture and has the added benefit of suppressing weed growth, as well. The irrigation systems recommended for use in vegetable gardens include drip irrigation, soaker hoses, or careful hand-watering. Foliage should be kept as dry as possible to reduce disease issues.

Fruit Crops
Most fruit crops require between 75% and 100% of ET to produce well. Newly planted trees will require more frequent irrigations, while established plants perform well with infrequent, deep waterings. It is useful to irrigate fruit crops using drip lines or basins. Maintaining consistent soil moisture in root zones until trees and vines become established is important, though soil can be allowed to dry out between waterings without adverse effects while plants are young. With established crops, however, water stress can cause issues with yield and fruit size. Soil moisture must be maintained while fruit is setting and growing, though soil should not be fully saturated. Mulched trees require significantly less water than trees growing in bare soil; mulch should be kept about 2-4 inches away from the trunk of fruiting trees and should be 2-4 inches thick on top of the soil. During extended periods of drought, fruiting plants are susceptible to developing issues with insect infestations and diseases if they do not receive adequate amounts of water. Although some can survive due to drought-resistance and can survive on one or two summer deep waterings, others like plums and peaches will be overly stressed. For more information on specific water needs of fruit crop species, see the individual listings in the Plant Identification modules.

Landscape Trees, Shrubs, and Ground Covers
Many commonly grown woody plants and non-turf ground covers need about 50%-60% of ET once they are established. New plantings require frequent irrigation so that their root ball and the soil around it are adequately moist during the first season. In the first month, these newly installed plants may need daily waterings, lessened to 1-3 times per week for the remainder of the first year in the ground. As these plants mature, deeper and less frequent irrigation is recommended at a depth of 1-3 feet. This will encourage deep, healthy root systems to form and make them more drought-resistant as a result. Tree roots spread out laterally beyond the drip line of a tree, so they should be irrigated outward as well as downward. The objective here is to water slowly so that moisture extends into and just beyond the root zone. What will happen with established trees if they are watered for short periods of time is that they will establish more shallow root systems, which can lead to water stress more quickly in drought situations.

Every 10 to 14 days in the summertime, mature trees should receive enough water to wet most of their root zone. Lawn sprinklers will not provide enough water to adequately irrigate these trees. Trees growing in turf will need additional waterings every 4 to 6 weeks or so in the summer, depending on temperature and how much water the lawn around them is receiving. In spring and fall, trees require less water and during wintertime, irrigation can be reduced greatly. Mulch should be applied 2-4 inches thick around these plantings and be kept 2-4 inches away from plant parts. If possible, trees should be watered separately from surrounding plants, as they have very different water needs. A garden hose, micro- or mini-sprinkler, deep-root irrigator, or drip system works well for trees. Lawns and other plants should be kept at least a foot away from tree trunks to discourage waterborne disease and reduce water competition. Special considerations should be made for trees and other woody plants growing in close proximity to building walls, driveways, sidewalks, or other structures. Re-radiated heat in these situations can increase the water demand for plants. Another factor that increases water needs for established plantings is fertilizing. Avoid applying fertilizer routinely to established trees, and also avoid engaging in unnecessary pruning during times of drought, as these activities will increase water needs.

Lawns
Lawns take the most water to keep healthy out of any plantings in the garden. This is in part due to incorrect, uneven watering. Cool-season grasses like tall fescue, annual and perennial ryegrass, bluegrass, and bentgrass require 20% to 30% more water than do warm season grasses like bermudagrass, zoysiagrass, and St. Augustinegrass. Cool-season turf requires 80% (65% for minimal coverage) of ET and warm-season turf requires around 60% (36% for minimal coverage) of ET. Significant water conservation can be achieved if a cool-season grass lawn is converted to a warm-season grass lawn. For a full guide on watering lawns, see the page linked below.

Lawn Care

Watering during drought restrictions

Plants that do not receive enough water will eventually show signs of water stress, like wilting, yellowing and browning of leaves, and poor fruit production. Water-stressed plants must be provided with water at an early stage of deficit to prevent irreversible damage, and it is crucial to regularly check plants for signs that they are water-stressed. These symptoms will be most noticeable in the afternoon. Symptoms to look for include:

Wilting or drooping leaves that do not return to normal by the evening.

Curled or chlorotic (yellow) leaves that may fold or drop, or foliage that becomes greyish and loses its green luster.

New leaves that are smaller than normal.

Lawn grasses that keep a footprint for more than a few minutes.

An important phenomenon to note is temporary wilting in hot, dry days. Even when plants have enough soil moisture, they sometimes on these extremely warm days will exhibit some wilting. Roots of these plants (which tend to be broadleaf ornamentals, bedding plants, and large-leaf veggies like cucumber and squash) cannot physically take in enough water quickly enough to replenish what is lost through stoma on leaves. Affected plants will recover when temperatures cool down in the evening and overnight. Adding additional water to these plantings will not correct the problem, and it may saturate the soil so much that plants are deprived of oxygen. There are other ailments that can mimic water stress in plants, such as verticillium or fusarium fungal infections, or other plants and diseases that damage plant vascular and root systems. Checking soil moisture in the root zone of the pant is necessary to determine whether wilting is due to water stress or these other issues. If soil is moist or the plant does not respond to watering within a day, other causes of wilting may be at work.

Under drought restrictions, plants may begin to get water-stressed, though most mature perennial plants can and will survive short periods on lower amounts of water, especially if adequate amounts of water are applied during the other seasons of the year. Mature trees can survive one season with only one or two deep waterings to 1-2 feet deep towards the drip line, though they will endure severe drought stress and even death if two years pass on this minimal watering schedule. Drought-stressed trees are very susceptible to damage from diseases and insects. Fruit and nut trees grown for harvesting will not produce nearly as much during years of drought as they will in normal watering years. The main goal with these trees is to simply keep them alive during the drought years; harvesting can wait until water is more available.

Most established shrubs will be able to hang on through long periods of dry soil. Thorough springtime waterings and one or two deep waterings in summertime should be sufficient to keep them alive and performing well for at least one season. Established warm-season grass lawns will go dormant in the summertime if water is not adequate, but will rebound with lush growth when rainfall increases. They can survive on 20%-30% of optimal water requirement for moderate periods of time. Cool-season grasses will show drought symptoms earlier; they require about 20% to 30% more water than warm-season grass lawns. These lawns will enter dormancy quicker and thin out under prolonged water stress. The recovery of these lawns is directly related to how long they were drought-stressed. Other groundcovers can survive on about half of the amount of water they would normally receive under optimal conditions, although some dieback can be expected. These plants should be watered at least once every 3-6 weeks from the months of April through September. Large beds with vegetables or annuals (or a combination) are tough to keep alive during drought restrictions, as these plants require more water than others. It may be necessary during times of drought to sacrifice these plantings or reduce their size in order to allow available water to be directed to more valued or expensive long-term perennial plantings.

graywater use in landscapes

In California, the use of graywater to irrigate landscapes is growing in popularity. The term graywater refers to wastewater from clothes washing machines, bathtubs, showers, and sinks (and excludes wastewater from toilets, kitchen sinks, and dishwashers). Under our safety code, graywater is defined as:

"Untreated wastewater that has not been contaminated by any toilet discharge, has not been affected by infectious, contaminated, or unhealthy bodily wastes, and does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes."
- Health and Safety Code 17922.12

The use of graywater is considered a green alternative to irrigating landscapes with water out of the faucet, and can lower water bills dramatically (depending on how much water you're using to irrigate your property). About 90 gallons of graywater are produced in the average household of 2.6 people each day, and while this may not be enough to irrigate all landscapes, those gardens that are low-water use without turf can be well-covered.

All About Graywater

building runoffs and drains
planning irrigation in your landscape

water conservation

Water management is a task that stretches far beyond the confines of our gardens. How water flows across land is of vital importance to communities and cities across our state and country. In addition to the water cycle of plants, there is an environmental water cycle, as well. This water cycle shows the continuous movement of water within the Earth and its atmosphere. It is a very complex system that includes many different processes, and is affected by myriad variables. In its most basic form, liquid water evaporates into water vapor, which then condenses into clouds, and precipitates back to earth in the form of rain and snow. Water, like soil, is a fragile natural resource that many people take for granted. Luckily, there is an entire industry dedicated to studying and conserving water resources. The study of how water runs across landscapes is known as hydrology, which is a very important sister science to horticulture in the gardening world.

As horticulturalists, we are concerned with the flow of water across landscapes, and how water infiltrates the soil to support plant life. However, there is another large factor to consider when planning, caring for, and providing water to a garden that affects the entire ecosystem. Runoff is the draining away of water and the substances carried in it from the surface of the ground or another building or structure built on the ground. Runoff occurs when there is more water than the land can be expected to absorb.

Runoff typically is highest during human activities like irrigating gardens or washing cars, and also occurs during rainstorms. Every city handles their runoff differently, due to the unique geographical and topographical qualities of the area. Runoff typically ends up draining into lakes and rivers through smaller creeks, drainage systems, and tributaries. All of the bodies of water in a given area plus the land that surrounds them are collectively called a watershed. Watersheds are all around (and sometimes underneath) us, and are commonly called catchments or river basins. They typically are areas of land surrounded by higher elevations (called drainage divides) from which water drains into a common body of water like a lake, river, ocean, bay or wetland area.

Watersheds consist of all surface water, including lakes, rivers, streams, reservoirs, and wetlands, and all of the underlying groundwater, as well. Watersheds are important to understand because the flow of water and the water quality of a watershed is greatly affected by the activities occurring on the surface of the land. There are many attributes and processes of watersheds that impact both water quality and availability. Both humans and the wildlife around us depend on the water within a watershed, but in order for this water to be useable, it has to be of good quality. Sources of pollution within watersheds are classified as either point source or nonpoint source pollution. Point sources are places that discharge to waterways directly from a pipe or other containment.

Businesses and industries that produce chemical waste that have the potential to pollute waterways have point sources that are regulated by federal and state agencies under the US EPA's Clean Water Act. The laws, regulations, and voluntary efforts by businesses have helped to clean up major water quality problems by reducing the amount of pollutants directly discharged into surface water and groundwater. However, a third of our country's water sources are not meeting water quality standards. Nonpoint sources are the culprits behind this failure. Nonpoint sources, as the moniker suggests, do not come from a specific source. Instead, this water originates from many places or from a widespread runoff area. It is often quite difficult to trace the exact origin of these pollutants because they result from a wide variety of human activities on the land as well as natural characteristics of soil, climate, and topography. Nutrients, microorganisms, and toxins are some of the most common contaminants of water, which can taint aquatic habitats and even our drinking water.

During rainfall, water quality is usually impacted because as rain flows over impervious surfaces like hard-paved roads, driveways and parking lots, or buildings and other structures, it can't soak in to the material, and instead runs over the surface, picking up whatever particles had previously settled there. These particles and other items include trash, debris, pet droppings, pesticides, fertilizers, herbicides, oils, soaps, ash, and other contaminants, which are then all dumped into the nearest waterway. The first rain of the season, usually after several months of dry weather, is especially toxic, and can be particularly problematic for water quality and aquatic life in urban streams and other runoff areas.

In addition to surface water quality being affected by nonpoint sources, groundwater can be impacted as well. The ability of pollutants to reach our water sources is enhanced by the amount of precipitation and urban runoff present in an area. During these activities, pet waste, decaying organic matter, and fertilizers dump unnatural levels of nutrients into our waterways. While small amounts of nutrients can actually be somewhat beneficial for aquatic plant life, larger amounts can lead to poor water quality, algal bloom outbreaks, and associated fish die-offs.

Water in California

Water is a critical resource in any state, but in California, it also drives and shapes our culture and economy. The growth of the state has been historically tied to the development of its water resources, starting with the arrival of immigrants from the eastern areas of the country in the late 1800's and early 1900's. It quickly became apparent, with this increase in population, that certain regions' water supplies could not support large groups of people. California receives most of its water (about 75%) through rain and snow received north of Sacramento, but 80% of the demand for water comes from the lower 2/3 of the state. Most of our rivers are also in the northern part of the state, and the most active agricultural areas (which bring in a lot of California's revenue) are in the center of the state. These areas of abundance and need are balanced through an intricately planned system of canals, dams, reservoirs, pumping plants, and aqueducts.

In the 1930's, the federal government built the Central Valley Project (CVP) to support the fertile agricultural lands in California's Central Valley. This project transports water from Lake Shasta in northern California down to Bakersfield in the southern San Joaquin Valley. This 400-mile multi-purpose network reduced flood risks while supplying needed water to residential and agricultural developed land. The Colorado Aqueduct, also built around the 1930's transports water from the Colorado River to Southern California's Metropolitan Water District.

In the 1960's and 1970's the State Water Project (SWP) kicked off, set to supply water to more than 27 million residents and 750,000 acres of farmland. This is one of the world's most extensive systems of dams, reservoirs, power plants, pumping plants, and aqueducts and boasts the world's tallest water lift at the Edmonston Pumping Plant.

In addition to this system of artificially-directed water, California has 190 watersheds (and many more sub-watersheds), ranging in size from small creeks to the San Francisco Bay. These watersheds are all divided into ten major hydrologic regions. More can be learned about each of these individual regions on the California Water Library website. Although California is a state that prides itself on green initiatives and has one of the most sophisticated water infrastructures in the world, it struggles to keep its waterways clean. The state of California is ranked ninth among all other states with the most estimated urban runoff in the country. Due to the amount of pollution that is transported in runoff, this creates a large ecological problem in the areas into which our watersheds empty. Individual homeowners are some of the biggest contributors to this pollution, which also means that the avenue for restoration of local healthy ecosystems is also in the hands of residents.

Tips and Practices for MAnaging Runoff

Gardeners around the globe have an amazing opportunity to greatly improve the water quality in their immediate surroundings by both reducing the amount of runoff they produce and increasing the quality of water that drains from their property. The following ideas can easily be built into the practices of residential gardeners:

Fix leaky faucets and other irrigation equipment to cut down on wasted water.

Ensure that during irrigation, runoff is not occurring. All applied water should be absorbed into the soil on the property.

Plant native plants that use less water to survive in the area.

Add large plants and shrubs to the property to increase soil moisture retention.

Do not allow workers on your property to dump wastewater into the gutters on the street.

Pick up pet droppings as soon as possible after they are deposited, or at least before the next irrigation occurs.

Plant species that are known for preventing erosion, especially if the property is sloped.

Create catchment areas for water on your property to allow more time for on-site percolation.

Reduce the square footage of paved or nonpermeable ground on your property.

Dispose of unused household chemicals safely and correctly.

Keep the soil on your property healthy and able to absorb water.

Dispose of any trash on the property promptly and correctly.

Place catchment pans under leaky cars or other machinery, especially in outdoor areas.

Use rain management systems to reduce water runoff during storms.

Recycle used antifreeze and motor oil instead of dumping them down the drain.

Carry doggie bags with you during walks, and dispose of them properly.

Opt for using compost over synthetic fertilizers to provide nutrients to plants.

Where possible, use natural materials for landscaping projects.

Avoid plastic furniture and dyed fabrics when choosing patio sets.

Stormwater Management Systems: Rain Gardens and Bioswales

Stormwater is the water that runs off of the ground after precipitation (rain, hail, or snow), and is considered to be a neighborhood nuisance because it can carry with it a lot of pollutants. Managing the stormwater that flows across a residential property is a critical step in reducing flooding in the area, cutting out pollutants that enter our waterways, and can also help to lessen the additional water needed to irrigate a landscaped space. Both Rain Gardens and Bioswales seek to manage rainwater runoff by mimicking nature, but there are some key differences in their applications. Rain Gardens are types of basins that are designed to capture and infiltrate storm runoff. The general idea is that a shallow depression is excavated and lined with an easy-draining soil mixture of topsoil, sand, and compost. Then, hardy native plants are added to the mix. When a storm passes through, precipitation is collected in the garden, is filtered through the spongy soil, and is slowly released back into the ground. In short, these types of garden areas are aesthetically pleasing ways to ensure ecological health. The bonus is, they are simple to install and virtually effortless to maintain.

Bioswales are similar in that they slow down rainwater flowing across a landscape, but they are arranged in a long channel or trench-like configuration. These areas also have vegetation planted in them and are aesthetically pleasing, commonly used in lettings such as along roadways, in large business parks, or other shared public spaces. While they are popularly used in many situations, the makeup and structure of Rain Gardens are more suitable for residential landscaped areas. For more information about creating these ecologically-sound landscape features, see the page linked below:

Stormwater Management

pools, ponds, and water Features

Managing water in a garden also refers to the creation and maintenance of water features like pools, ponds, waterfalls, fountains, and sources of drinking and bathing water for wildlife. Garden water features can enhance the aesthetic, auditory, and relaxation aspects of a space just from their presence, and also have added benefits like a cooling effect, air quality improvement, noise reduction, increased property value, and

Fountains
There is a large market for garden fountains; they can be found just about anywhere nowadays. Fountains are one of the most common types of water features for homeowners across the United States, due to their ease of installation and maintenance. Fountains do a great job at providing auditory relaxation (and possibly noise-cancellation) and can be designed to be as large or as small as is desired.

Water Gardens and Fishponds
Water gardens are gardens (or areas of the garden) with plants that live in and around water. These features are best incorporated into natural landscapes, and enable homeowners to add plants like water lettuce, water lilies, horse tail, blue iris, and sweet flag to their landscapes. Fishponds are also incorporated into natural settings, and contain many of the same plants. An added bonus of these water features is that they can house beautiful species of fish that are mesmerizing to watch. Fishponds can add expense and more maintenance, due to the fact that live animals are being kept. Beyond stocking the pond with fish, a pump will be needed to circulate water, and vegetation will be necessary to add oxygen to the water and provide a natural food source. Fishponds, depending on where they are located, may also need some netting or other protection from predatory animals like birds, coyotes, and even neighborhood cats. On the plus side, these features will also bring in non-predatory wildlife to the yard.

Waterfalls and Streams
These larger water features create a natural, meandering setting that can help connect areas of the landscape. Functionally, these features can also double as bioswales or rain garden catchment areas. These features are a little more difficult to install, and typically require professional help.

Water for Wildlife
There are many features that can double as useful places for animals and insects to drink, bathe, and raise their young. Ponds attract a variety of wildlife, from frogs to water insects to songbirds and even birds of prey. Herons have been known to visit larger backyard water features. Bird baths and other shallow dishes provide places for birds to bathe and can also double as bee and butterfly water stations. Check out the ideas below for some inspiration:

Best Practices for Backyard Water Features
Water features are relatively low-maintenance parts of landscapes, though there are a few things to keep in mind when designing one for your space to make care and cleaning a breeze:

Cleaning. Water features should be cleaned every one to three months. Adding liquid algae products is also useful in keeping these water features clean, as long as the products are safe for wildlife and pets. Larger water features like ponds, pools, and troughs should be deep cleaned every spring and fall.
Inspection. Inspect water features regularly for issues like algae growth, cracks or leaks, water level, and temperature.
Checking Pumps. Pumps can easily become clogged with debris that falls into the water feature. Filters and screens can reduce this issue, but do not completely eliminate it. If screens are used, they should be cleared of debris regularly. If there is any change in water level or any noise emitted from the pump, check it immediately. If water features are turned off for the winter, store the pump indoors to prevent it from being damaged by the expanding and contracting quality of freezing and unfreezing water.
Keeping Water Moving. Static features such as ponds that are meant to be still should have water circulated with a pump. Aerating water reduces algae buildup and prevents mosquito larvae from hatching. It can also attract birds more effectively than a stagnant pond of water. If there are fish in the pond, they will need a certain level of aeration to breathe properly. Each fish species varies in their needs for water aeration, so make sure to talk to an aquarist about the specific needs of the fish you keep.
Shading. Providing shade for a water feature decreases the water evaporation it will experience - especially in the warmer months of the year. Ideally, about 60% of the water feature should be shaded. Typically, it is normal to lose about 2-5 inches of water per week, depending on weather, pond size and location. Shade around water features can be achieved through placement near a building or other structure, adding a shade screen above the feature, or adding plants, shrubs and trees that will provide shade. Shading a water feature also has the benefit of keeping the water temperature down and discouraging algae to grow.

Plants for In and Around Water Features
There are many plants that will do well around water features like ponds and streams. These plants prefer to 'dip their toes' from time to time, and enjoy moist soil conditions. Plants with very little leaf and flower litter (as well as those who don't drop sap) will be best for planting around water features, as less cleanup will be required to keep the pool and its pump system clean. Some great California native plants to install around water features include: