Water Infiltration

Water infiltration is a measure of how quickly water penetrates soil, which is a crucial part of the small water cycle. This process affects the soil’s ability to capture and hold moisture, influencing groundwater recharge, runoff, and soil moisture distribution. These factors play a vital role in plant growth, nutrient availability, and overall ecosystem health.

Assessing and then monitoring water infiltration gives us insight into the soil’s ability to utilize the precipitation it receives. The amount of precipitation that is infiltrated into the soil, and hence available to crops for growth is known as effective precipitation. Precipitation that is lost to runoff or evaporation from the soil surface is not accessible to plants and must be removed from the total amount of precipitation received when considering precipitation from a plant or crops point of view.

Water infiltration can vary greatly across an area (e.g., a field) and is strongly impacted by the activities that take place on the land. It is therefore a great candidate for monitoring for those interested in assessing the impact of the various practices being used or trialed. Water infiltration is also affected by our movements across the land and the compaction we create. In order to account for this variability, we recommend using the three-ring, three-pour method to ensure that you’re accounting for some of the variability across your area/field of interest and aren’t getting biased results by placing a single ring in an area that happens to be highly compacted or unusually well aggregated. Looking at water infiltration can help assess localized and area-wide trends and identify areas of most and least concern.

Theory: By pouring a premeasured ~450ml* of water into a 6 inch wide, 6 inch tall ring sunk half way into the ground we are able to approximate the effect of a 1” rain on the soil and observe how long it takes for the water to infiltrate into the soil. Second and third pours simulate 2” and 3” rains respectively and demonstrate how soil responds as water infiltrates deeper into the ground.

Practice: Water infiltration tests can be done anywhere there is an interest. Infiltration will change throughout the seasons and is strongly influenced by precipitation. Make sure to take note of recent weather conditions. Tillage will also alter results and should be noted. Once you’ve chosen your site:

• Lay out the rings across the site avoiding areas that have clearly been compacted such as track rows, compacted areas etc (or take note of how these areas infiltrate differently).
• Make sure each ring is on level ground and goes in straight.
• Do not disturb any thatch or plant material on the surface. If needed, use a sharp blade to slice around the ring through plant material to allow the ring to make contact with the soil.
• Place a piece of wood (2×4) over the ring (to protect the ring) and use a mallet to hammer it into the soil ~ 3” (it is useful to have the 3” line marked on each ring).
• Place the plastic liner in the ring and fill it with the pre-measured water.
• Gently remove the plastic liner, letting the water run into the ring and immediately begin timing.
• Once all the water has been absorbed (no shiny/glistening spots left on the soil) stop the timer and record the infiltration time. Repeat in all three rings for 3 consecutive pours.

Notes:

• Tillage will “fluff up” the top portion of the soil profile causing water to infiltrate rapidly on the first pour. Note how water infiltration may slow down on subsequent pours as water reaches the untilled soil.
• The plastic liner is used to prevent the act of pouring the water into the ring from eroding soil and affecting results. In high winds (where plastic is cumbersome) you can use your hand to break the impact of the water pour on the soil.
• When pounding in the ring, make sure that you are not disturbing the soil. If the soil is so hard that it is “bouncing” as you pound, make sure to note this and consider how it may affect your results.
• Avoid choosing areas with rocks or large roots. These will make pounding in the ring impossible and will also affect your results.
• Make sure not to disturb the area where you place the ring. Avoid stepping there and if you’re using a penetrometer at the same time, make sure not to place the ring in a location where the penetrometer was inserted into the soil.
• If you’re wondering if your infiltration rate is good or bad, compare it to a nearby unmanaged site with similar soil conditions. The unmanaged site will show the “natural potential” of a similar soil and give you a standard to aim for. The difference between your field and the unmanaged site can be interpreted to be the impact that management has had on the soil in your field.

* 463 ml for rings with an inside radius of 7.62 cm and 444 ml for rings with an inside radius of 7.45 cm

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How Much Water Do You Need?
The volume of water needed to assess infiltration at a rate of 1 inch of rain will vary depending on the size of the ring you’re using. You can use a ring of any diameter, but it should have a minimum height of 5-6 inches. However, larger rings are preferred because their larger surface area makes it easier to monitor the water as it infiltrates.

Water Volume Equation
To calculate the volume of water you need to represent 1 inch of rain, use the following formula:

This equation is based on the the volume of a cylinder with a water height of 1 inch (2.54 cm), where “r” (radius) is equal to half the INSIDE diameter of the ring you’re using and is reported in cm in order to calculate volume in ml (metric to metric!).

Background Information
To calculate the volume of a cylinder, we used the following formula:

In this case h = 1 inch or 2.54 cm.

The above formula can be simplified to:

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Why Monitor This Metric:
Assessing and then monitoring water infiltration gives us insight into the soil’s ability to absorb
water and hence the effectiveness of precipitation on our soils. Water infiltration can vary greatly
across an area (e.g., a field) and is strongly impacted by the activities that take place on the land.
It is therefore a great candidate for monitoring for those interested in assessing the impact of the
various practices being used or trialed. Water infiltration is also affected by our movements across
the land and the compaction we create. Looking at water infiltration can help assess localized and
area-wide trends and identify areas of most and least concern.

Tools and Materials:
● 3 metal rings (6” diameter x 6” depth)
● Rubber mallet
● Block of wood (2×4)
● Timer + backup timer (preferably 1 timer for each ring)
● Knife
● Water bottle (preferably 1 for each ring)
● Water jug (large enough to hold water for at least 3 pours at each of 3 rings on all sites you
plan to visit)
● Tote/Bucket (to carry everything)
● Shovel
● Pencil/Marker/Pen
● Paper
● Clipboard
● Plastic sheet ~ 18” square
● GPS or phone with geolocation capabilities
● Ruler
● Rag or towel

Measuring Water Infiltration:

The 3-ring, 3-pour Method
We recommend using the 3-ring, 3-pour method to measure water infiltration. Water infiltration can
be highly variable in managed landscapes. Using 3 rings helps to account for this. Using 3 pours
addresses variability that may occur within the first few inches of soil and the ability of soil to
infiltrate water deeper into the soil.

Placing the Rings
● Place each ring on a level patch of ground avoiding any areas of compaction or holes/
cracks in the ground.
● If following the ROO baseline establishment protocol, you will select locations near
subsampling sites 3, 6 and 9. If not following the ROO baseline establishment protocol,
select locations for the three rings that are several meters apart but still close enough
together to allow you to easily monitor all three rings. Unless you are specifically interested
in investigating the effect of compaction on water infiltration, avoid high traffic areas
including wheel tracks, field approaches and pivot paths etc.
● If you’re setting up a baseline for your farm/field, ensure that rings are placed in areas
where the soil conditions are representative of the area.
● Cut away any plant material that may interfere with the ring’s placement – making sure not
to disturb any soil. Infiltration rings can be placed between crop rows to minimize disturbance to plants.
● Use a rubber mallet to gently drive the ring into the soil to a depth of three inches. Placing a
piece of 2×4 wood on top of the ring helps prevent damage to the ring and the mallet, and
keeps the ring level as it enters the soil. Take care to ensure the ring is evenly seated and does not wobble.

Setting Up to Measure Infiltration
● Line a ring by placing a plastic sheet inside it, drawing the edges of the sheet up and over the edges of the ring. Using a plastic liner prevents the action of pouring water into the ring from eroding
the soil in the pour location and confounding your results. It also ensures that the
entire volume of water comes into contact with the soil at the same time.
● Pour the pre-measured water (450 ml) into the ring and carefully remove the liner to initiate
the infiltration process. 450 ml of water represents the equivalent of 1 inch of rain in the 6 inch diameter ring.
● Start timing immediately after removing the liner.
● Infiltration can be extremely variable. Some sites are able to infiltrate the full 450 ml in a
matter of seconds, other sites may take a half hour or more to fully infiltrate.
● Depending on the rate of infiltration, you may now be able to repeat the above procedure for
your remaining two rings.
● Make sure someone is keeping an eye on all three rings and is ready to stop the timer the
moment the water is fully infiltrated.
● You will know when infiltration is complete when there is no more “glistening” on the surface
of the soil inside the ring.
● Record the time it took for the water to infiltrate on your data sheet. Use a prepared data sheet or a notebook to record the time it takes to infiltrate each pour of water in each ring. Note your observations and make sure to record the location and date.
● Once infiltration is complete, proceed with the second and then the third pours following the
procedure outlined above.

Making Observations
● During the infiltration process, take a closer look inside your ring and note the following: What do you observe (e.g., critters, plant material, clarity, presence of bubbles)? What do your observations indicate (e.g., bubbles indicate air displacement and porosity, slower second pour may indicate compaction or silt particles forming a seal on the surface between pours)? What patterns do you notice between the first, second, and third pours?
● Record your observations as well as any variations in water absorption rate or soil
conditions for each pour.

Calling it Quits
● When water infiltration is slow, it may not be a reasonable use of your time to spend an hour
waiting in a field for water to completely absorb. If during any of your pours, infiltration is not
complete by the time 20 minutes have elapsed (for that pour), consider ending the
monitoring of that ring there.
● Record your infiltration time as 20 minutes with a note indicating you “quit” at this point.
● To quantify how much water remained to be infiltrated, use a small ruler to measure the
depth of water remaining inside your ring.
● Record this depth on your data sheet along with any observations as to why infiltration
might be so slow at this specific location.
● If this occurs during pour 1 or 2, do NOT proceed with subsequent pours.
● Compile all recorded data, including infiltration times, observations, and any noted
anomalies, into the data sheets for analysis.

One Final Observation
● Using a shovel to free the ring from the soil gives you the chance to see how the water
behaved as it infiltrated into the soil.
● Is there any indication of spillage or leakage beyond the ring that might indicate there was
“looseness” when it was placed?
● To what depth did the water infiltrate? Did it continue below the bottom of the ring?
● How does the soil appear – does it look more like chocolate pudding or chocolate cake after
receiving the equivalent of 3” of rain?

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Materials:

□ 3 – steel rings 6” diameter – 6” depth

□ 3 – timers – one for each ring

□ 3 – graduated water bottles marked at 1” of water equivalent

□ 1 – mallet for inserting rings

□ 1 – sheet for recording data

□ 1 – plastic sheet used to cover soil while pouring water

□ 1 – laminated instruction sheet

Additional requirements:

□ bucket or container to carry kit materials to field site

□ short piece (8”-10”) of 2”x4” wood to place on top of ring while pounding ring into soil

□ water jug to carry minimum of 5 litres of clean water for 3 reps of 3 rings

□ camera to take photos for reference

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We have created a handy printable water infiltration sheet for you to track the results of your pours. Access it by clicking the button below.

To download the data sheet, please click the button below:

Interpreting the results from your water infiltration monitoring is all about comparison. In areas with well aggregated soil, a 1 inch equivalent of water can be infiltrated in a matter of seconds. In areas with high levels of poor aggregation, infiltration of the same amount of water can take more than an hour! You may want to consider calling it quits after 15-20 minutes if you’re most interested in looking for general trends.

If using water infiltration monitoring to inform your on-farm management decisions, we suggest two things.

(1) Assess the variability between the rings in the same field. Do you see fast infiltration in some rings and slow infiltration in others? This is a frequent observation in cultivated areas and indicates an opportunity for improvement (ie, reducing variability by implementing practices such as growing polycrops or cover crops, keeping soil covered and more!)

(2) Compare results from your in field water infiltration monitoring to results in a nearby unmanaged area with similar soils etc. How do they compare? Healthy unmanaged areas reflect the potential of your soil under existing environmental conditions.