Simple Soil Infiltration Tests That Guide Water Harvesting Fixes

Simple field fixes such as cover crops, residue retention, buffer strips and careful machinery use can dramatically decrease runoff and erosion while simultaneously helping protect soil fertility and water quality.

Infiltration testing is an integral component of designing stormwater infiltration practices, providing us with an idea of the amount of water soaking into the ground.

1. Dig a hole

Infiltration testing is an integral component of designing a bioretention system. Infiltration rates provide important insights into soil structure, whether macropores, micropores and earthworm channels are channeling water deeper into the ground – which ultimately means less erosion, sedimentation and runoff from surfaces as well as improved overall health of soils.

To measure infiltration rates, either a soil pit or borehole method must be carried out. When conducting soil pits, all debris and weeds should be cleared out from within them before pouring water into them and timing its drainage rate; an alternative test option could include using permeameter testing instead.

The test involves using a circular device with an outer secondary ring to allow water to gather at its center and measure water movement from edges toward center. All debris and weeds must be cleared away before timing how long it takes for water depth of three inches is measured.

Results from various tests should be compared in order to establish an average infiltration rate for the site. It is preferable to use median data rather than arithmetic mean; as the infiltration rate of individual holes can change considerably over short distances due to changing soil conditions.

2. Fill it with water

Water harvesting requires careful observation and action to be successful, but infiltration tests can provide valuable guidance on how to improve soil structure and encourage slowing and spreading rainwater for infiltration rather than running off land erosively. Small strategies help slow the flow of water thus reducing erosion, nutrient loss and septic tank overloading.

PIT (Pilot Infiltration Test) is an efficient way to assess infiltration rates. This involves digging a hole of equal dimensions as the proposed infiltrative surface (10 feet by 15 feet bottom dimensions), filling it with water, and timing its drain-off time – using this data, engineers can determine pre-construction infiltration rates and design accordingly; however, this process is both costly and time consuming.

Modified Phillip-Dunne Permeameter provides another method for measuring infiltration rate: using a metal cylinder driven two inches deep into the ground and filled with water, it measures how long it takes for it to drain back out as an indicator of saturated hydraulic conductivity.

Although the results of this simple test may not be as precise, they still provide valuable insights into the quality and quantity of water harvested from a site. Furthermore, it can help pinpoint causes for reduced infiltration such as soil compaction at depth or blocked earthworm and root channels.

3. Measure the time it takes for the water to drain

Soil infiltration is determined by gravity, capillary forces, osmosis and absorption processes that vary according to soil texture, structure and moisture content. A number of soil characteristics influence these processes; texture, structure and moisture content all have an effect. Sand soils tend to have higher infiltration rates due to larger pore spaces in their structure compared to clay ones due to greater absorbency; particle size also plays a part as smaller particles allow less infiltration while compaction, crusting or lack of pore space can reduce water absorption capacity in some ways.

As soil becomes saturated, infiltration rates decrease over time and eventually stop entirely once saturation point has been reached. This point can vary depending on several factors including soil type and depth as well as duration of rainfall event.

As such, infiltration rates can differ dramatically across short distances, even when soil appears uniform. To accurately measure infiltration rate, a soil pit must be dug and filled with water using devices like double-ring infiltrometer or modified Phillip-Dunne permeameters – Ahmed et al (2011) conducted tests on various devices used for infiltration that overestimated true saturated hydraulic conductivity; they suggest geometric mean estimates as better indicators. Understanding infiltration process takes knowledge, practice and patience – an infiltration device won’t do.

4. Record your results

Water infiltration tests are an indispensable way of understanding soil structure and improving its ability to absorb and hold water. Slowing, spreading, and infiltrating rather than eroding off our land’s surface is key for productiveness, health, and resilience on any farm – this can be achieved through improved soil health, earthworm channels and organic matter as part of water harvesting strategies. For more information about bringing nature back onto your land or ecological agriculture strategies in general take one of our online courses on soil health, organic chemistry or natural cycles – an excellent starting point for new farmers or students wanting to learn more about ecological agriculture!