NPS Photo/Cookie Ballou Deserts and water are intrinsic opposites, each defining the other, in a relationship that is distinct, dramatic, and dynamic. While representing the best protected example of the Chihuahuan Desert, Big Bend National Park’s intricate geological, natural, and cultural histories are water driven. Few places on earth offer such a premier example of this relationship as the association of the Rio Grande and the desert in Big Bend. The geological history of Big Bend is very complex and reflects the importance of water in geological processes. Geologist Ross Maxwell conducted the first major study of Big Bend’s geologic history during the early years of the park’s development. Maxwell noted in his book The Big Bend of The Rio Grande that only recently has man appreciated the role of water in the formation of rocks through sedimentation. Throughout geologic time spanning many millions of years, vast deep oceans and shallow seas have recycled the eroded sediments from surrounding mountains forming the rich limestone ranges as seen near Persimmon Gap, Boquillas, and Santa Elena Canyon. Water was also important during Big Bend’s volcanic era some 38 million years ago in that rising magma contacting the water table caused huge steamy explosions, rearranging the landscape into fantastic shapes seen along the scenic Ross Maxwell Drive. While water creates new rock, its erosive nature is best evident in the deeply etched canyons characterizing the Rio Grande. Water has been a major influence in Big Bend’s vibrant natural history. The deep oceans and shallow seas dominating Big Bend’s early geological history left rich fossil treasures such as ammonites, mollusks, ancient petrified trees, and dinosaur bones. All life evolves in response to environmental pressures, and 10,000 years ago Big Bend’s environment began the slow process of drying out which resulted in today’s Chihuahuan Desert. The desert encouraged wildlife adaptations; a life of limited water, a life of conservation, a life of hardiness. Succulent, waxy surfaces, small leaves, spreading root systems, deep root systems, dormant lifestyles characterize arid adapted plants; animals evolve smaller body sizes, are active at night, or metabolize water from their foods in response to water or the lack of it. Water’s influence today is reflected in the amazing transformation of a lifeless-appearing desert into a verdant, life-filled landscape immediately after a rain. Abundant rain provides food in the form of seeds, berries, nuts, and succulent grasses, perpetuating a complex food chain. It was the rich landscape that attracted man. Cultural history is defined by man’s presence, and man first ventured into Big Bend as the climate dried. At that time, the Rio Grande was naturally free flowing with plentiful water, its few tributaries thriving and fertile, allowing early cultures access to the resources necessary for existence. Archeological finds mirror man’s link to water; thousands of Native American habitation sites abound—all within reach of a water source. Spanish explorers followed, finding thriving communities of farming Native Americans irrigating their fields of corn and squash along the river’s banks. By the 1880’s, man’s grasp for water was nearly complete in Big Bend as all major water sources supported the western advance into a still isolated frontier. These hardy souls endured isolation and hardship, seeking opportunity as cattle ranchers, homesteaders, farmers, and miners using the natural resources and water with impunity to fuel a growing nation. By the mid 1920’s, the rich desert grasslands were disappearing due to overgrazing; the tree-lined streams were denuded and drying. Man hoped it would rain to replenish the land, renew the streams and fill the river; hope in the renewing power of water continued through the 1940’s until it became clear that nature was more powerful than hope. Today, water is still in short supply, and unable to meet the increasing demands of man’s growth. The Rio Grande flows with less water today than 20 years ago. Many reliable springs no longer flow or flow only intermittently. Invasive exotic species such as saltcedar monopolize springs, soaking up water, transforming soils to salt beds; feral hogs and trespass livestock dig up or trample springs, disrupting the delicate balance required to keep them flowing. Sheet flooding after a downpour rearranges and erodes the exposed desert soils because the soil holding grasses has disappeared. Our water challenges are being addressed with efforts to re-establish the once magnificent desert grasses and control the exotic species of plants and animals. Monitoring springs, recording river flows, water quality and quantity are tools for managing the resource. The water issues facing Big Bend National Park are not easily solved and reflect a growing concern with all of earth’s water. With sound conservation practices, public awareness and time, one day the mighty Rio Grande, the rich desert grasslands, and the clear flowing streams and springs may recover. Water pays little heed to time and only time will tell. |
Last updated: February 24, 2015