CENTER FOR BIOLOGICAL DIVERSITY
For Immediate Release July 9, 2005
San Pedro River Runs Dry for First Time near Fort Huachuca
Arizona’s last surviving desert river in trouble as USGS’ Charleston Narrows gage registers zero flow for the first time in recorded history
Contact: Dr. Robin Silver, CBD Board Chair, 602.246.4170 firstname.lastname@example.org
Stream flow measurements from the Charleston gage east of Fort Huachuca go back to March 29, 1904. For the first time since recordings began in 1904, San Pedro River stream flow at this gage has disappeared.
The Charleston gage is located just to the east of Fort Huachuca in an area known as the Charleston Narrows. Bedrock there at the surface of the river channel forces the San Pedro River’s entire sub-surface flow to the surface. San Pedro River stream flow at the Charleston Narrows is the most sensitive indicator of the health of the Upper San Pedro watershed’s groundwater aquifer. For the first time in recorded history, the San Pedro River has run dry at the Charleston Narrows.
This new development follows the recent revelation that the cone of depression resulting from the excessive deficit groundwater pumping in the Fort Huachuca/Sierra Vista is now directly affecting San Pedro River base flow.  Base flow is the stream flow during the driest times of the year. On June 1, 2005, Fort Huachuca released groundwater monitoring well data showing that the excessive local groundwater pumping in the Fort Huachuca/Sierra Vista area is causing groundwater levels to drop adjacent to River at the eastern edge of the Base.
Fort Huachuca’s groundwater monitoring wells are located adjacent to the San Pedro River, the USGS’ Charleston gage and the Charleston Narrows. The interpretation of Fort Huachuca’s monitoring well data that the Fort Huachuca/Sierra Vista cone of depression is directly affecting the San Pedro is supported by newly reviewed U.S. Geological Survey (USGS) data showing reduced water seeping from the regional aquifer to the San Pedro River in the Lewis Springs area. Lewis Springs is located upstream from Fort Huachuca on the San Pedro River.
The San Pedro River is the last surviving free flowing, un-dammed desert river in the Southwest. The San Pedro flows through the center of the watershed within which Fort Huachuca is located. The San Pedro stream flow reflects the surface of the area’s groundwater aquifer, or the water table itself. San Pedro River stream flow during the driest times of the year seeps directly from the groundwater aquifer into the River. Groundwater from this aquifer is the only source of water in the area. Excessive, unmitigated and increasing, local groundwater pumping from this aquifer threatens the San Pedro River. The groundwater pumping deprives the San Pedro River of surface flow due to the existence of a direct hydrological connection between the water in the area’s underground aquifer and the surface water, or actual stream flow, in the River. As pumping lowers the aquifer level or water table, stream flow is diminished.
According to 2003 USGS data released on November 18, 2004, the deficit has increased by 134.3% to -12,050 acre-feet per year, from -5,144 acre-feet per year as cited in the August 23, 2002, Biological Opinion. Not surprisingly, San Pedro River base flow has been decreasing dramatically.
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