Falcon Reservoir

The ranchos that were excavated in 1950 and 1951 were destroyed by the construction of Falcon Dam, and many more sites like them were soon submerged when Falcon Reservoir was filled. Falcon Reservoir also covered several hundred prehistoric archeological sites along the banks of the Rio Grande, as well as two small towns. In all, an area stretching over 40 miles on both sides of the Rio Grande was impacted by Falcon Reservoir.

Due to health and safety concerns caused by submerged structures to boaters, the United States Sector of the International Boundary and Water Commission instituted a program of leveling standing structures within the reservoir basin during the 1950s.  The program did not anticipate the passage of federal laws designed to protect cultural resources a decade or two later.  Most building on the United States side of the reservoir were either dynamited or bulldozed; whereas those managed by the Mexican Sector of the IBWC were left intact.  Differences in the management concerns has resulted in the periodic reemergence of churches and structures from the town site of Guerrero Viejo on the Mexican side of lake during low-water episodes, whereas the ruins of ranchos on the United States side appear as mere rubble piles of stone.   

During the 1990s, the sites of the Falcon area were to suffer further destruction. Waters of the reservoir reached record low levels, exposing hundreds of sites including cemeteries, Spanish Colonial ranchos, and prehistoric sites that had been submerged for nearly 40 years. In addition to disturbances caused by pounding waves and eroding shoreline, the historic and prehistoric sites were exposed to an even more destructive menace—pillaging by looters and commercial artifact collectors. Even though most buildings on the Spanish Colonial ranchos were destroyed, many of these sites contain deposits with antique artifacts, and gravesites.  All of these remains became open targets for plunderers when the water levels dropped.

In an attempt to assess the damage and determine how to stop the destruction, a team of archeologists and mapping specialists from TARL, the Texas Historical Commission, the National Park Service, the Southern Texas Archaeological Association, and the Texas Archeological Stewards Network joined together in an unprecedented effort. Their week-long survey in 1996 along the Falcon shorelines resulted in the documentation of 40 Spanish Colonial, Tejano, and other sites. Although the group proposed a comprehensive plan for site protection to the International Boundary Waters Commission, the damage already done to the sites was, in some cases, immeasurable.

In their report, archeologist Dr. Tim Perttula and members of the survey team wrote:

The frenzied activities of the looters and collectors have damaged and/or destroyed an untold number of archeological sites at Falcon reservoir, threatening the very fabric of the prehistoric and historic cultural heritage of this part of the Rio Grande Valley and calling into question whether the material expression of this heritage can be preserved and protected for future generations to appreciate and study.

Today, the reservoir continues to fluctuate in level, a process which in itself is destructive as sites are exposed, then resubmerged. Inundation of archaeological remains is detrimental to the preservation of bone, shell, wood and especially metal remains. But the degree of impacts from shoreline erosion caused by wave action associated with fluctuating water levels varies depending upon the slope of the landform, and the site's exposure relative to prevailing winds.