How to Build a Swale Step‑by‑Step (High Desert Edition)

by Grace Whitfeld

A companion to “Reading the Land for Water”  

For Concho • St. Johns • Apache County • 5,700 ft elevation

Once you’ve learned to read the land — to see where water naturally wants to move, pause, and soak — the next step is shaping the earth so that every drop of rain becomes a gift to your soil.

A swale is one of the simplest, most powerful tools for harvesting rainwater in the High Desert. It’s nothing more than a shallow, level trench on contour with a berm on the downhill side. But this humble shape can:

• Slow runoff

• Recharge groundwater

• Reduce erosion

• Support trees and shrubs

• Bring life back to dry soil

And the best part?

You can build one with nothing more than a shovel, a level, and a little patience.

Here’s how to build a swale step‑by‑step, tailored specifically for our High Desert climate.

🌄 1. Choose the Right Location

Use the clues from your land‑reading:

• Look for natural water pathways

• Find gentle slopes (5–15% is ideal)

• Avoid areas where water pools too long

• Stay clear of septic systems and foundations

• Place swales above gardens, trees, or future planting areas

A swale should feel like it belongs there — not forced.

📏 2. Mark the Contour Line (This Is the Most Important Step)

A swale must be perfectly level from end to end so water spreads evenly.

Use one of these simple tools:

A‑Frame Level

• Three sticks + string + a rock

• Works beautifully in the field

• Mark the ground every time the legs read level

Water Level

• Clear tubing filled with water

• Perfect for longer swales

Carpenter’s Level + Long Board

• Good for short distances

Walk the contour slowly, marking it with:

• Flags

• Rocks

• Flour

• Spray paint

This line is the backbone of your swale.

🪣 3. Dig the Swale Trench

Now the fun begins.

Depth:

6–12 inches is perfect for the High Desert.

Width:

18–24 inches for small swales

3–4 feet for larger ones

Shape:

• Flat bottom

• Gently sloped sides

• Level from end to end

Place all removed soil on the downhill side — this becomes your berm.

🧱 4. Build the Berm

The berm is what holds water in place long enough for it to soak in.

How to build it:

• Pile the excavated soil on the downhill side

• Shape it into a long, smooth mound

• Tamp it gently with your feet

• Add rocks to stabilize if needed

• Keep the top slightly rounded

A well‑built berm is sturdy but not rigid — it should feel like part of the land.

🌱 5. Test Your Swale With Water

Before planting anything, test it.

Use:

• A hose

• A bucket

• A monsoon rain if you’re lucky

Watch how the water behaves:

• Does it spread evenly?

• Does it pool too deeply?

• Does it escape at the ends?

Adjust the contour or berm as needed.

This step saves you hours later.

🌿 6. Plant the Berm and Basin

Plants stabilize the soil and help water infiltrate.

On the berm (downhill side):

Choose drought‑tolerant shrubs and perennials:

• Apache plume

• Four‑wing saltbush

• Rabbitbrush

• Desert willow

• Penstemon

• Globemallow

Their roots anchor the berm and drink deeply.

In the basin (the trench area):

Plant species that love occasional soaking:

• Native grasses

• Wildflowers

• Herbs

• Shade‑tolerant shrubs

Avoid planting right against the uphill wall — leave space for water to spread.

🪨 7. Add Mulch or Rock Armor

Mulch helps slow evaporation and protect soil.

Use:

• Wood chips (thin layer)

• Juniper needles

• Gravel

• River rock

Rock lining is especially helpful in windy areas or where erosion is strong.

🌧️ 8. Observe After the First Storm

This is where the real learning happens.

After a rain, walk your swale and look for:

• Overflow points

• Erosion on the berm

• Areas where water didn’t spread evenly

• Spots where sediment collected

Make small adjustments — swales evolve with the land.

🌵 9. Expand Slowly

Once your first swale is working beautifully, you can add:

• A second swale downhill

• A third swale uphill

• Crescent catchments around trees

• Rock rundowns in erosion channels

• Micro‑basins for native shrubs

A network of small features is more effective than one large one.

🌟 Why Swales Work So Well in the High Desert

Swales honor the natural intelligence of the land.

They:

• Slow water

• Spread water

• Sink water

And in a place where every drop matters, that’s everything.

Over time, swales create:

• Greener vegetation

• Healthier soil

• More wildlife

• Less erosion

• Cooler microclimates

They turn dry ground into living ground.