Understanding Aquifer Recharge
In many areas worldwide, aquifer depletion is a critical challenge for agricultural production. Understanding how quickly aquifers are recharged is essential to assessing depletion risks, but it’s one of the most difficult parts of the water cycle to measure.
UNL hydrogeologist John Gates studies the world’s aquifers to understand groundwater recharge, whether he’s investigating drainage below a single irrigated field or the health of an entire groundwater system.
“Aquifers that receive no recharge are nonrenewable resources, analogous to fossil fuels,” Gates said. “By determining the rate of groundwater renewal, we are able to assess the long-term viability of irrigated agriculture.”
Gates primarily studies arid regions, where precipitation is relatively scarce. In these areas, periodic storms can recharge groundwater aquifers. Gates and UNL meteorologist Adam Houston are teaming to study how storms affect recharge.
“If we want to achieve predictive capability about recharge in arid areas, we have to get on top of this issue of episodic recharge,” he said.
COLLABORATING IN CHINA
In northern China, Gates works with researchers to improve the efficiency of irrigation, which relies on groundwater. Decades of heavy irrigation and increasing urbanization have strained the region’s aquifers, which recharge too slowly to sustain current use rates.
Determining groundwater age helps Gates understand recharge rates. Using techniques such as radiocarbon dating of water-soluble carbon picked up as water passes through the soil, he calculates the water’s age based on changes in isotope compositions over time. “Isotopic tracers let us unravel how long groundwater has been in an aquifer.”
In contrast to aquifers in northern China, most of the High Plains Aquifer in Nebraska receives sufficient recharge for the time being, thanks largely to its sandy soil.
“We do have some hot spots of depletion around the state,” Gates said. “But Nebraska is fortunate to have naturally high recharge rates.”
More details at: http://go.unl.edu/j5j