The researchers found evidence that, from around 1890 to 1960, overgrazing and resultant soil degradation, not encroachment by woody plants, were the main culprits behind reductions in streamflows and recharging of groundwater in the semiarid central region known as the Edwards Plateau. The region is the primary water source for the Edwards Aquifer, which supplies the city of San Antonio and numerous smaller municipalities.
Large numbers of cattle, sheep, and goats that continuously grazed the area's rangelands led to widespread soil degradation, partly hindering the amount of water recharging springs and groundwater, says hydrologist Bradford Wilcox of Texas A&M University and Texas AgriLife Research, in College Station, Texas.
He and Yun Huang, a former graduate student at Texas A&M, will publish their results in an upcoming issue of Geophysical Research Letters, a journal of the American Geophysical Union (AGU).
From 1880 to 1900, there were more animals on the land than it could support, Wilcox says. For a short period of time near the turn of the last century, stocking rates were 10 times greater than current levels. Since the late 1900s, however, as fewer cattle and other livestock were used on the land for agricultural production, the region has gone through revitalization.
"As a result, these landscapes are recovering, but they've also converted to woody plants," Wilcox notes. "We're also seeing large-scale increases in the amount of spring flows. This is opposite of what everybody is presuming -[which is that] the trees are there sucking up all of this water. The trees are actually allowing the water to infiltrate."
In fact, spring flows are twice as high as they were prior to 1950, he adds.
"This area was basically converted from grassland to shrubland after many years of heavy livestock grazing. What people have forgotten is that in the time period between healthy grasslands and the current shrublands, there was an extended period when the land was quite degraded. Subsequent to 1960, livestock numbers have declined and the landscape has recovered although there are now more cedar than in the past," Wilcox explains.
In the new study, he and Huang, who is now with LBG Guyton, in Austin, assess the hydrological changes that have taken place in the region as patterns of land use and vegetation changed. To do so, the researchers analyzed annual measurements dating back to 1925, or earlier, for the Nueces, Frio, Guadulupe, and Llano rivers. The measurements provide an annual record of 'baseflow,' or flow derived from groundwater only (i.e. springs) and of 'stormflow' or flow resulting from rainfall, for those rivers.
The scientists report that the total flow in the three of the four rivers has gone up in recent decades, "largely because contributions in the form of baseflow have increased." The baseflow of the fourth river also increased, although its total flow did not. Yet, rainfall in the region hasn't changed significantly.Although the prevailing wisdom has been that proliferation of woody plants stifles infiltration of water back into aquifers, the new results suggest otherwise.
Moreover, the results have implications beyond the Edwards Plateau, Wilcox and Huang maintain, applying in general to "semiarid and subhumid rangelands in which springs and intermittent or perennial streams are found." For such regions, the transition to woody plants appears to be good news for regional water resources.Images:
Peter Weiss | American Geophysical Union
By saving cost and energy, the lighting revolution may increase light pollution
23.11.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Frictional Heat Powers Hydrothermal Activity on Enceladus
23.11.2017 | Universität Heidelberg
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
23.11.2017 | Information Technology
23.11.2017 | Physics and Astronomy
23.11.2017 | Life Sciences