The Watershed Approach to Landscaping – Part I

Editor’s note: This is the first in a multi-part series on Watershed Landscaping from our partners at G3, Green Gardens Group. This post covers the basics of the watershed approach, including definition, importance, and residential approaches.

By Pamela Berstler

Swales or dry creek beds serve an important function in the landscape. Photo: Tara Collins
Swales or dry creek beds serve an important function in the landscape. Photo: Tara Collins

We know that our individual landscapes play a critical role in the health of both the watershed we live in and the earth as a whole, yet we often don’t see how the simple practices of gardening in our front yards could possibly influence climate change! We’re too little and the problem is too big, right?

The Watershed Approach (WA) to landscaping allows us to change landscapes, which are often thought of as “ornamental,” into multi-benefit environmental solutions.   But why the heck are we calling it “watershed” approach? It sounds so weird, and we’re used to “water wise.”

The use of the term “watershed” allows us to shift away from a water conservation-centric discussion of landscaping (which honestly feels like a lot of sacrifice) into a more integrated resources conversation (which feels like a change with big benefits).

The best thing about using the Watershed Approach on individual properties is that those properties now become part of a bigger solution, acting together to make communities more resilient.

What is a watershed

The Environmental Protection Agency defines a watershed as:

“An area land that drains to a common waterway, such as a stream, lake, estuary, wetland, aquifer, or even the ocean.”

Using this definition, any area of land, every property, regardless of size or land use (every front or back yard, every roof top) can be described and regenerated as a “mini-watershed” using agreed upon principles of watershed management.  These principles unite water managers, watershed managers and flood control, developers, landscapers, horticulturalists and property owners behind one mission that goes beyond sustainable and water wise principles. The best thing about using the Watershed Approach on individual properties is that those properties now become part of a bigger solution, acting together to make communities more resilient.

Why is the Watershed Approach important

The Watershed Approach sets new priorities for landscapes; these are:

  1. The intention to gather as much rainwater as possible in every landscape, and
  2. The intention to optimize the availability of water for cycling back into the atmosphere via evapotranspiration.
Photo: G3, Green Gardens Group
Photo: G3, Green Gardens Group

In nature, a healthy balanced watershed allows precipitation to pass through a highly-developed system of plants and “living soil” (soil alive with microbial and fungal activity) before it either moves through the system into a local waterway or groundwater, or is held in the soil profile for evapotranspiration by the plants.  The water that is slowed by plants and soil before moving into groundwater or nearby waterways is cleaned by the microbial activity of the plants and soil, so water quality is improved.  That water which is held in the soil, is transpired by the plants back into the atmosphere where it is able to continue the cycle of precipitation – eventually forming clouds, condensing, and falling back to earth.

Principles of the Watershed Approach

 After setting an intention to gather all the rainwater that falls on a property and put it into the soil, the principles of the Watershed Approach can be applied:

Photo: G3, Green Gardens Group
Photo: G3, Green Gardens Group

1. Build healthy Living Soil that is biologically diverse and has developed a structure like a sponge

This is best accomplished by adding organic matter to the soil.  Spongey soil structure is perhaps the most critical principle of the Watershed Approach to landscaping, as it primes the system for holding or releasing rainwater, sequestering and cycling carbon and nutrients, and promoting the incredible biodiversity that is necessary for plant resiliency. Also, a 1% increase in soil organic matter holds 16,000+ gallons of water per acre to a depth of one foot; that is a critical resource for plants to thrive during seasonal drought, and survive during extended dry conditions.

Photo: Tom Rau
Photo: Tom Rau

2. Treat rainwater as a resource rather than a waste product

Since our intention is to hold on to as much rainwater as possible, this may seem as a no-brainer.  It’s important to remember the simple methods by which rainwater is retained on a site. Retention is best accomplished by creating small divots, swales, basins, and contours.  Make sure that impermeable surfaces are either made permeable or used as capture areas for redirection of water into the landscape. When we treat rainwater as a resource, we need to plan for capturing ALL of the rainwater.  Rainbarrels and cisterns may be necessary to temporarily store quantities of rainwater that eventually can be released back into the landscape over time.

Photo: G3, Green Gardens Group
Photo: G3, Green Gardens Group

3. Plant climate appropriate plants, preferably local natives

Local natives are adapted to the soils, rainfall and weather patterns of a particular place.  They are symbiotic with the other flora in their community, and the fauna that rely on that community.  They also are symbiotic with the fauna and flora of the soils.  This makes local natives the very best choice for landscape resilience. Perhaps more importantly, local natives, planted in their natural communities, are able to work together by sharing carbon, water, and nutrient resources through a soil-based microbial and fungal network.

Photo: Pamela Berstler
Photo: Pamela Berstler

4. Use highly efficient irrigation, only when necessary

The “only when necessary” is important to think about.  If you are capturing rainwater, building healthy living soil, and selecting plants that are in sync with your local climate, you may not need to install an automatic irrigation system; in fact, rainwater passively collected in your soil may be your only source of water.  However, since climate change is altering weather patterns, even local native plants in the best biologically active soil will struggle during periods of prolonged drought.  That means, many California natives in garden settings will do best if provided supplemental water during the winter months if there is extended drought and during the fall through spring months, if rainfall is minimal.

Irrigation efficiency is determined by how effectively the water applied to a landscape actually gets to where it is meant to go. Drip irrigation emitters, low-flow valves, weather-based irrigation controllers, back flow preventers, low head check valves, and soil-based moisture sensors are all part of efficiently designed, installed, and managed irrigation systems.

Drip irrigation Photo: Pamela Berstler
Drip irrigation Photo: Pamela Berstler

Another aspect of efficient irrigation is the selection of the supplemental water source.  Irrigation that draws from rainwater or gray water is a better choice than a new system that uses drinking water. And finally, management of the irrigation system is critical!  Irrigation systems are not to be built and forgotten; they need to be actively and constantly managed in order to be watershed wise.

Applying the Watershed Approach

In future posts, we will discuss how healthy Living Soil contributes to the resilience of local native plants, and how Watershed Approach landscapes can alter weather patterns and contribute to reversing climate change.

 


Pamela Berstler is the CEO of G3, Green Gardens Group, Executive Director of Pacific Horticulture Society, and Founder of the Urban Soil Summit.

5 Comments

  1. Bravo for the well written article and pictures!

    We teach about watersheds in elementary schools and places like Birch Aquarium
    and Heal the Bay in Santa Monica. But, we don’t talk about it enough with
    home gardeners. Watershed gardening relates to doing something about helping
    wildlife too by building a mini wildlife corridor — trying in a small way to mitigate
    the fragmented wildlife habitats that have been lost to human development.

  2. Great article about an insightful, appropriate and productive perspective on ‘landscaping’! I love it and look forward to the rest of the articles in your series – thank you!

  3. I was told that drip irrigation is terrible for CA natives. Occasional spray with a micro irrigation system to wash off dust from plants is acceptable. Is that correct?

    1. Hi Nicole,

      There are many differing opinions and experiences when it comes to irrigating California native landscapes. Drip irrigation can be used, but it takes a thorough understanding of the site conditions to get it right. There is a common misconception that drip systems are very easy to use, and can be set and forgotten. This is often not the case, however, and we have heard about issues and failures when drip systems are not set up and used appropriately. Instead, many native plant gardeners have found it easier to hand water, or use micro-spray or high efficiency nozzles rather than install a drip system. An occasional sprinkling with either the hose or spray irrigation can be helpful to dusting off plants, particularly in the summer months when there is little rainfall and many natives prefer the drier conditions.

      Thanks,
      Kristen

Post A Comment