Study confirms groundwater pumping linked to river, stream depletion
This is another excellent article from Shar Porier of the Sierra Vista Herald Tribune on the San Pedro River. Shar has produced a number of articles on the San Pedro River this year that are related to the water rights adjudication hearing that took place. In light of the BLM's release of the Record of Decision and Approved Resource Management Plan for the San Pedro Riparian National Conservation Area (SPRNCA) at the end of July, I think this article is timely as it continues to highlight the link between the health of the San Pedro River and groundwater pumping. The text of the article is below as is a link to the actual article which has another sidebar with information from another hydrologist on this topic.
SIERRA VISTA — “Arizona’s water myth is that people believe they can pump ground water without affecting surface water.”
That assessment by hydrologist T. Allen J. Gookin’s was made some years ago, as legal proceedings to determine the San Pedro River’s navigability as a waterway before the Arizona Navigable Stream Adjudication Commission.
For decades, the meandering river has been the subject of numerous studies and has been proclaimed by many scientists as probably, the most studied river in the Southwest.
A host of federal, state and local governments and agencies, along with environmental groups, have all come to the same basic conclusion in their analyzations over the past three decades — the root of the health of the river grows up from the aquifer.
Now, a new study by Laura E. Condon, University of Arizona Department of Hydrology and Atmospheric Sciences, and Reed M. Maxwell, Groundwater Modeling Center at the Colorado School of Mines, offers another substantiation of the connection.
The authors produced the report, “Simulating the sensitivity of evapotranspiration and stream flow to large-scale water depletion.”
“Groundwater pumping has caused marked aquifer storage declines over the past century,” according to the report. “In addition to threatening the viability of groundwater-dependent economic activities, storage losses reshape the hydrologic landscape, shifting groundwater surface water exchanges and surface water availability. A more comprehensive understanding of modern groundwater-depleted systems is needed as we strive for improved simulations and more efficient water resources management.”
Their study hinged on isolating impacts of “decreased groundwater storage on the hydrologic landscape and start to unravel the hydrologic differences between modern, depleted, groundwater systems and natural watersheds.” They produced a modeling simulation which shows the impact groundwater levels to land surface disturbances.
In their research, they found roughly 200 cubic miles of water was withdrawn from aquifers across the United States over the 20th century. Depending on a finite source with an infinite–use state of mind leads to groundwater losses. Combined with varying climate conditions, the problem is exacerbated.
“The long–term storage losses caused by a century of groundwater development can be viewed as a large–scale reshaping of the integrated hydrologic landscape. This will influence watershed response to both natural and human perturbations moving forward. This study seeks to isolate the impact of decreased groundwater storage on the hydrologic landscape and start to unravel the hydrologic differences between modern depleted groundwater systems and natural watersheds,” they say.