When it comes to water and rainfall, scientists aren't sure exactly how it travels when it seeps beneath the ground. Now, scientists have used a laser to help reveal how water travels through soil beneath the ground.
Soil itself is made up of different particles. These particles include sand, silt and clay. Within the soil is also organic matter, which includes plant litter, soil microbes and other organisms. The rest of soil is made up of air and living roots.
The flow of water beneath the soil is important to understand. This is largely due to agriculture and the fact that water can carry excess fertilizer beneath the ground and even seep into groundwater. In addition, this water travel allows researchers to estimate how long it may take to refill aquifers and how they may respond to climate change.
"There are a number of reasons why more accurate predictions of water flow is important," said Daniel Hirmas, one of the researchers. "Better management of resources is one."
In order to better understand the flow of water within the soil, called preferential flow, the researchers turned to a multistripe laser triangulation (MLT) scanner. The scientists took saturated soil and then allowed blue dye to flow through the sample. This allowed them to see the actual flow of the water.
So what did they find? It turns out that scanner revealed pores allowing the dyed water to pass through; this revealed a preferential flow pattern.
"The soil structure affects how easily water can be transported through soil," Hirmas said. "This is called 'hydraulic conductivity. Conductivity is a property of the soil. It affects how quickly water can be transported through the soil. Saturated hydraulic conductivity refers to the conductivity of the soil when the soil is fully saturated with water. In this case, all the soil pores are filled with water."
The findings reveal a bit more about soil hydrology. The scanner itself can map soil macroporosity, which can tell researchers a bit more about how soil filters water. This, in turn, will allow scientists to make predictions about water movement.
The findings are published in the March 2016 journal Vadose Zone Journal.
