Why water soaks into sand faster than clay

Water enters soil through the spaces between particles. Sand has large pores that let water pour in quickly, while clay has tiny pores that pass water slowly even though they can hold a lot of it. When rain falls faster than the soil can take it in, the extra ponds on the surface and runs off, carrying soil and nutrients with it.

Controls

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Rainfall intensity

Storm total

Soil for the readouts

Step through it

SandLarge, well connected pores let water in quickly, often more than 20 mm per hour. Sand rarely ponds, but it holds little water for crops.
LoamA mix of sand, silt and clay with moderate pores. Water enters at a middling pace and much of it is held for plants.
ClayVery fine particles leave tiny pores. Once the surface wets, water creeps in at only a few millimeters per hour.
A summer downpourAt 60 mm per hour even loam cannot keep up, so most of the storm runs off instead of refilling the root zone.
A gentle soaking rainAt 5 mm per hour sand and loam absorb everything as it falls. Clay still ponds, a little.

Infiltration rate by texture

When soil is dry, water enters fast because suction pulls it into empty pores. As the topsoil fills, the rate settles toward a steady value set mostly by pore size. Physically based models such as Green and Ampt describe that early drop; this model skips it and uses typical steady rates of about 25, 7.5 and 2.5 mm per hour for sand, loam and clay.

Those are representative values from published ranges, and real soils vary a lot with structure, organic matter, crusting and compaction. The runoff readout is simplified too: it assumes a steady storm, ignores water stored in surface puddles, and counts whatever falls faster than the soil can absorb.

Try it: set the rainfall to 24 mm per hour and switch the readouts between Sand, Loam and Clay. Sand absorbs everything, loam sheds about 70 percent of the storm, and clay sheds about 90 percent.

Building better infiltration

Cover crops, residue and less tillage protect the surface from crusting and feed earthworms and roots that make larger channels. Over a few seasons that can noticeably raise how fast a field takes in water, which means less runoff and more water stored for the crop.

Where Avid uses this

As a USDA NRCS Technical Service Provider for conservation planning, Avid deals with infiltration and runoff when choosing practices for a field.

Sources

Irrigation Chapter 3: Soil WaterUniversity of Nebraska-Lincoln, Plant and Soil Sciences eLibrary
A Field Method for Measurement of Infiltration (Water-Supply Paper 1544-F)USGS Publications Warehouse
Soil Health: Infiltration (Guides for Educators)USDA NRCS

How to cite this model

Avid Solutions International. (2026, November 11). Why water soaks into sand faster than clay [Interactive 3D model]. Avid Field Lab. https://avidsolutionsintl.com/explore/soil-infiltration

Last updated November 11, 2026

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