Understanding water's movement through soil
Cody A. Ross
Studying the path water takes after a rainstorm can be crucial in understanding its movement through different types of soil and can ultimately help guide water management decisions. Cody Ross, a Ph.D. student in the Department of Geological Sciences and a member of the Watershed Systems Research Program at the University of Manitoba, is studying the way water flows through the vadose zone, the layer of soil beneath the land’s surface. SWS Managing Editor Amy McIntosh asked Ross about his research.
Amy McIntosh: How are you monitoring the movement of water in your study?
Cody Ross: In our study, water movement was monitored using meteorological data, hydrometric data, stable water isotope signatures and fluorescent dye concentrations.
Meteorological data allowed for the quantification of water inputs. Stream water level and water table levels were monitored using wells and loggers to monitor water level dynamics and riparian to stream interactions. Waters from each of these sources (i.e., rainfall, snow, groundwater) were analyzed to establish their individual isotopic signatures, which allows for the quantification of source contributions to the stream water that is the combined mixture from all sources.
Finally, two types of fluorescent dyes were used: one was applied to the ground surface and the other was injected into groundwater wells. Those dyes do not occur naturally, so monitoring dye concentrations in the stream gives an indication of how quickly surface and subsurface waters reach the stream compared to one another.
McIntosh: Why is it important to understand how water moves through soil?
Ross: How water moves through the soil is important for a variety of reasons. Soil characteristics can influence how quickly water moves through the soil and how much water can enter the soil. Those two factors alone have significant implications for plant growth and flooding. Additionally, there are interactions between soil and water that influence water quality. As water moves through soil, both vertically and laterally, the water is susceptible to contamination from soils that contain natural or human-added chemicals.
McIntosh: What is the significance of the runoff’s age?
Ross: The age of water is significant because it informs us about the path that water has taken. Old water has taken a longer path and was present in the watershed prior to the snowmelt or rainfall event that resulted in its discharge to the stream. In contrast, new water is water associated with a given event and has travelled a shorter path before arriving to the stream.
McIntosh: How can understanding how water moves impact water management decisions?
Ross: Understanding water movement allows for informed management decisions, especially in times of water scarcity and surplus. It can inform us on how quickly and how much water reaches a stream following an event. That information is valuable for infrastructure design, drainage network operation and flood response. How water moves also informs us on the source and mechanism of water contamination that is valuable for managers concerned with water quality.