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Monsoon rains found to be beneficial to underground aquifers

Monsoon rains found to be beneficial to underground aquifers

The same results that CLO found on the monitoring of washes and hillside trincheras are being found by a team in New Mexico. 

"The summer monsoon in the deserts of the southwestern U.S. is known for bringing torrents of water, often filling dry stream beds and flooding urban streets. A common misconception when observing the fast moving water generated by monsoon storms is that most of the water is swept away into large rivers, with very little of it percolating into underground aquifers.

Using a combination of field instrumentation, unmanned aerial vehicles and a hydrologic model, a team of researchers from Arizona State University and the Jornada Long Term Ecological Research Program of the National Science Foundation has been studying the fate of  and its impact on  in the Chihuahuan Desert of New Mexico.

Their findings, recently published in the journal Water Resources Research, explain how a surprising amount of rainfall, nearly 25 percent, from monsoon storms is absorbed into small stream beds and percolates into the  system. The researchers identified factors affecting the percolation process through the use of a numerical model that reproduced the long-term observations obtained at a highly instrumented research site.

"The results of this study show that  serve an important role in recharging groundwater aquifers near the point of runoff generation," says ASU hydrologist Enrique Vivoni of the School of Earth and Space Exploration and the School of Sustainable Engineering and Built Environment. "This is an essential process that banks renewable surface  for future use as a ground water resource in the arid Southwest and throughout the world."

Read more at: https://phys.org/news/2018-08-monsoon-beneficial-underground-aquifers.html#jCp

 

This article introduces the following new research publication: Schreiner-McGraw, A. P., & Vivoni, E. R. (2018). On the Sensitivity of Hillslope Runoff and Channel Transmission Losses in Arid Piedmont Slopes. Water Resources Research. https://doi.org/10.1029/2018WR022842

Abstract: Channel transmission losses alter the streamflow response of arid and semiarid watersheds and promote focused groundwater recharge. This process has been primarily studied in dryland channels draining large areas that are displaced away from hillslope runoff generation. In contrast, small watersheds on arid piedmont slopes allow the investigation of interactive hillslope and channel processes that control the partitioning between surface and subsurface flows. In this study, we utilize high‐resolution, long‐term measurements of water balance components in an instrumented watershed of the Chihuahuan Desert to set up, parameterize, and test a process‐based, distributed hydrologic model modified to account for channel losses. A transient method for capturing capillary effects in channels results in simulations with a reliable representation of the watershed energy balance, soil moisture dynamics, hillslope infiltration, channel transmission (or percolation) losses, and streamflow yield over the study period. The simulation also reproduces a conceptual model of hillslope infiltration‐excess runoff generation linked to downstream channel percolation losses that depend on the rainfall event size. Model‐derived thresholds were obtained for the amount of hillslope runoff (6 mm) and rainfall (12.5 mm) necessary for streamflow yield, such that 40% of percolation occurs for small events that do not reach the outlet. Using a set of scenarios, we identify that hillslope infiltration controls the rainfall threshold necessary to initiate percolation, while channel infiltration affects the partitioning into percolation and streamflow yield. Thus, the connectivity along hillslope‐channel pathways is deemed an essential control on the streamflow generation and groundwater recharge in arid regions with complex terrain.