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Rain Gardens: Maximizing Rainwater Harvesting in Spokane

At Dryland Revival, we are passionate about regenerative landscaping practices that not only beautify our surroundings but also conserve water and protect the soil. One of the most effective methods to achieve this is through the creation of rain gardens. In this blog post, we'll explore how rain gardens, along with earthworks, soil conservation methods, and strategic plantings, can be used to harvest rainwater efficiently. With Spokane receiving only 16-17 inches of rain annually, it’s crucial to make the most of every drop.


Brad Lancaster, a pioneer in rainwater harvesting currently residing in Tuscon, AZ (read: Hot & Dry), emphasizes the importance of working with nature to manage water resources. His work highlights simple solutions that can be implemented at home and in the community. Lancaster's principles can be applied effectively in Spokane to make the most of our limited rainfall. By using earthworks, improving soil health, and planting appropriately, we can create beautiful, functional landscapes that thrive without additional irrigation.

Image from Brad Lancaster's website:

According to Lancaster, in Dryland ecosystems it’s imperative to "Plant the rain before you plant the plant." This means designing your landscape to capture, store, and steward rainwater before adding vegetation. This strategy demonstrates a clear difference between passive and active rainwater harvesting, the former focused around earthwork and the latter all about storage in cisterns, barrels, and retention reservoirs. Each rainwater harvesting strategy has its place, necessitated by the future use of the space and the maintenance capabilities of the landowner. In today’s post we will be focused on passive rainwater harvesting. You can read another post on cisterns and rain barrels, here.

We highly recommend reading Lancaster's landmark work, Rainwater Harvesting (all 3 volumes!) if this topic is of interest to you. 


A rain garden at its most basic is a designed depression in the landscape that passively collects rainwater runoff directed from roofs, driveways, and other impervious surfaces. It is planted with deep-rooted native plants and grasses that tolerate both wet and dry conditions. This setup not only reduces erosion and filters pollutants but also helps in recharging the groundwater table.

Rain gardens play a significant role in erosion control. By slowing down and capturing rainwater runoff, rain gardens reduce the speed and volume of water flowing across the landscape. This decrease in water velocity helps prevent the soil from being washed away, maintaining the integrity of the landscape. The deep-rooted plants in rain gardens also stabilize the soil, further reducing the risk of erosion. 

This combination of slowed-down water and deep-rooted plants creates a recipe for water infiltration, better helping the water permeate into the soil instead of running off into our stormwater systems.


Earthworks are landscape features that shape the land to control and direct the flow of water. Techniques such as swales, berms, and terraces can direct and slow down water flow, allowing it to soak into the ground rather than running off. These methods are particularly beneficial in arid regions like Spokane, where conserving every drop of rainwater is essential. Each method has its advantages based on certain applications, and each drainage/erosion system is unique. It is pragmatic to study an area for quite some time to observe its hydrology and soil characteristics before deciding on what kind of earthwork you’d like to pursue to harvest rainwater.

Swales are shallow ditches designed to catch and hold rainwater, allowing it to infiltrate slowly into the soil. They can be planted with water-loving plants that further aid in water absorption and erosion control.

Berms are raised barriers of soil that prevent water from flowing away, redirecting it to areas where it can be absorbed. Combined with swales, berms create a dynamic system for rainwater management.

Terracing involves creating step-like areas on a slope, reducing water runoff speed and promoting infiltration. This method is particularly useful on hilly terrain, preventing soil erosion and making the most of available rainwater.


Healthy soil is crucial for effective rainwater harvesting. Practices such as mulching, composting, and using biochar improve soil structure, increase organic matter, and enhance water retention.

Mulching with organic materials like straw, wood chips, or leaves reduces evaporation, keeps the soil cool, and adds nutrients as it decomposes. We recommend using a mulch of some type within your rain garden.

Composting enriches the soil with essential nutrients, improves its structure, and increases its ability to retain water. We recommend using compost as you amend the soil within your rain garden.

Biochar is a soil amendment created through the process of pyrolysis of organic matter. Pyrolysis is thermal decomposition of material, in this case making useful soil amendment out of previously just dried plant matter. We recommend making biochar (if you have the resources to do so) or buying it, and amending the soil within your rain garden with it. It holds a ton of water and can be great for nutrient storage as well.  


Choosing the right plants for your rain garden is vital. Native plants are often the best choice as they are adapted to the local climate and soil conditions. In Spokane, consider species that can thrive with the available rainfall and are drought-tolerant once established.

Native grasses like Bluebunch Wheatgrass and Idaho Fescue are excellent choices for their deep root systems and ability to survive in dry conditions.

Shrubs such as Snowberry and Oregon Grape are hardy and provide year-round interest while supporting local wildlife.

Wildflowers like Yarrow, Blanketflower, and Lupine add color and attract pollinators, creating a vibrant and resilient ecosystem.

Wetland plants that can survive dry periods like Golden Currant and Red Osier

Dogwood are excellent to plant in a rain garden that will experience both wet feet and dry spells. 


Creating a rain garden involves several steps, synthesizing earthworks, soil conservation methods, and strategic plantings:

  1. Site Selection and Design:

  • Choose a low-lying area where rainwater naturally collects.

  • Ensure the site is at least 10 feet away from building foundations to prevent water damage.

  1. Earthworks:

  • Dig a shallow basin (at least 6-12 inches deep) to capture runoff.

  • Create swales to direct water into the rain garden.

  • Build berms around the edges to prevent overflow and redirect excess water.

  • Use locally sourced rocks and boulders to create permanence and increase aesthetic appeal.

  1. Soil Preparation:

  • Test the soil for drainage by filling the basin with water and observing how quickly it drains.

  • Amend the soil with compost, mulch, and biochar to improve its structure and water retention capabilities.

  • Mulch the area with organic materials to reduce evaporation and protect the soil surface.

  1. Plant Selection and Planting:

  • Choose native plants adapted to both wet and dry conditions. Incorporate a mix of grasses, shrubs, wildflowers, and trees.

  • Arrange plants according to their water needs, with more water-tolerant species at the bottom of the basin and drought-tolerant ones around the edges.

  • Ensure plants have enough space to grow and establish deep root systems.

  1. Maintenance:

  • Water the garden regularly during at least the first year until plants are established.

  • Monitor for weeds and remove them promptly.

  • Reapply mulch annually to maintain soil health and moisture levels.


Rain gardens offer an elegant solution for rainwater harvesting in Spokane. These gardens not only conserve water and prevent erosion but also enhance the beauty and biodiversity of your landscape. Incorporating passive rainwater harvesting to your garden adds both aesthetic appeal and functional benefits, making your garden a resilient and attractive space year-round. By following the insights of experts like Brad Lancaster, we can create sustainable, resilient gardens that make the most of our precious rainfall. At Dryland Revival, we are dedicated to helping you implement these and all regenerative practices, ensuring a greener, more sustainable future for our community.


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