Among these changes are rapid urbanization and continued exploitation of natural resources that include water resource development, conversion of wildlands to agricultural and forestry practices, mineral and energy production, urban and industrial expansion, recreational or leisure developments, and transportation infrastructure. Unfortunately, these land-use conversions have extensively modified the natural vegetation of entire regions.
For example, of the original Blackland Prairie, only about 0. Similarly, 95 percent of the native brush in the lower Rio Grande Delta has been lost to agricultural and urban development, increasing the value of the remaining brush as a habitat for wildlife, including many endangered species.
Although most of the eastern forested region is still timbered, about 66 percent of the bottomland hardwood forest has been cleared or replaced by reservoirs, tame pasture, and crops; much of the upland hardwood forest has been converted to pine plantations for commercial timber products.
Not only have native plants been displaced, but many have been replaced by alien species. Consequently, boundaries of many of the vegetation types are now changing rapidly-not as a result of natural changes in climate but because of human induced landscape-scale modification.
The great plant diversity and complex patterns of plant distribution in Texas developed in response to a matrix of complex environmental factors including geology, topography, climatic zones, rainfall belts, and soil types. There are more than 5, species of vascular plants trees, shrubs, vines, wildflowers, grasses, and grasslike plants such as sedges and rushes.
Of this number, about are endemic. Nearly half of the grass species indigenous to the United States occur in Texas. More than species of vascular plants are introduced. Unfortunately, many of these alien species have degraded or destroyed habitat for native plant species. The greatest number of plant species occurs in the Trans-Pecos and eastern forest regions. This pattern of floral diversity directly affects wildlife diversity and abundance.
The occurrence and distribution of plants in Texas supports more than 1, native vertebrate species and countless invertebrates that are dependent upon vegetation for food and cover. This vegetation and cover-type map represents a snapshot at an instant in time of the dynamic landscape at a regional level. Increased application of cover-type analysis for land-use decisions could improve the probability of achieving a long-term balance between socioeconomic considerations and natural resource needs.
Additional information concerning this map, such as detailed descriptions of each of the mapped plant associations and photographs of each association, is available on the Nature Section, Plant Life Unit of the Texas Parks and Wildlife Department website.
Frye, Kirby L. Brown, and Craig A. Geologists study the natural scenery of Texas and sort its variations into distinctive physiographic provinces. Each province or landscape reflects a unified geological history of depositional and erosional processes. Each physiographic province is distinguished by characteristic geologic structure, rock and soil types, vegetation, and climate.
The elevations and shapes of its landforms contrast significantly with those of landforms in adjacent regions. The Physiographic Map of Texas displays seven physiographic provinces and their principal subdivisions; the accompanying table describes their major physical differences. The following descriptions selectively emphasize those characteristics that distinguish provinces and their subdivisions. The Coastal Prairies begin at the Gulf of Mexico shoreline.
Young deltaic sands, silts, and clays erode to nearly flat grasslands that form almost imperceptible slopes to the southeast. Trees are uncommon except locally along streams and in Oak mottes, growing on coarser underlying sediments of ancient streams. Minor steeper slopes, from 1 foot to as much as 9 feet high, result from subsidence of deltaic sediments along faults.
Between Corpus Christi and Brownsville, broad sand sheets pocked by low dunes and blowouts forming ponds dominate the landscape. The Interior Coastal Plains comprise alternating belts of resistant uncemented sands among weaker shales that erode into long, sandy ridges.
At least two major down-to-the coast fault systems trend nearly parallel to the coastline. Clusters of faults also concentrate over salt domes in East Texas. That region is characterized by pine and hardwood forests and numerous permanent streams. West and south, tree density continuously declines, pines disappear in Central Texas, and chaparral brush and sparse grasses dominate between San Antonio and Laredo.
On the Blackland Prairies of the innermost Gulf Coastal Plains, chalks and marls weather to deep, black, fertile clay soils, in contrast with the thin red and tan sandy and clay soils of the Interior Gulf Coastal Plains. The blacklands have a gentle undulating surface, cleared of most natural vegetation and cultivated for crops. From sea level at the Gulf of Mexico, the elevation of the Gulf Coastal Plains increases northward and westward.
In the Austin San Antonio area, the average elevation is about feet. The eastern Grand Prairie developed on limestones; weathering and erosion have left thin rocky soils. North and west of Fort Worth, the plateaulike surface is well exposed, and numerous streams dissect land that is mostly flat or that gently slopes southeastward. There, silver bluestem-Texas wintergrass grassland is the flora.
Primarily sandstones underlie the western margin of the Grand Prairie, where post oak woods form the Western Cross Timbers. The Balcones Escarpment, superposed on a curved band of major normal faults, bounds the eastern and southern Edwards Plateau. Its principal area includes the Hill Country and a broad plateau. The Edwards Plateau is capped by hard Cretaceous limestones.
Local streams entrench the plateau as much as 1, feet in 15 miles. The upper drainages of streams are waterless draws that open into box canyons where springs provide permanently flowing water. Sinkholes commonly dot the limestone terrane and connect with a network of caverns. Alternating hard and soft marly limestones form a stairstep topography in the central interior of the province. The Edwards Plateau includes the Stockton Plateau, mesalike land that is the highest part of this subdivision.
With westward decreasing rainfall, the vegetation grades from mesquite juniper brush westward into creosote bush tarbush shrubs. Its side streams become draws forming narrow blind canyons with nearly vertical walls.
The Pecos Canyons include the major river and its side streams. Vegetation is sparse, even near springs and streams. The most characteristic feature of this province is a central basin having a rolling floor studded with rounded granite hills to feet high. Enchanted Rock State Park is typical of this terrain. Rocks forming both basin floor and hills are among the oldest in Texas. A rim of resistant lower Paleozoic formations see the Geology of Texas map surrounds the basin.
Beyond the Paleozoic rim is a second ridge formed of limestones like those of the Edwards Plateau. Central live oak mesquite parks are surrounded by live oak ashe juniper parks. An erosional surface that developed on upper Paleozoic formations forms the North-Central Plains. Where shale bedrock prevails, meandering rivers traverse stretches of local prairie. In areas of harder bedrock, hills and rolling plains dominate. Local areas of hard sandstones and limestones cap steep slopes severely dissected near rivers.
Lengthy dip slopes of strongly fractured limestones display extensive rectangular patterns. Western rocks and soils are oxidized red or gray where gypsum dominates, whereas eastern rocks and soils weather tan to buff. Live oak ashe juniper parks grade westward into mesquite lotebush brush. The High Plains of Texas form a nearly flat plateau with an average elevation approximating 3, feet.
Extensive stream-laid sand and gravel deposits, which contain the Ogallala aquifer, underlie the plains. Windblown sands and silts form thick, rich soils and caliche locally. Havard shin oak mesquite brush dominates the silty soils, whereas sandsage Havard shin oak brush occupies the sand sheets.
Numerous playa lakes scatter randomly over the treeless plains. The eastern boundary is a westward-retreating escarpment capped by a hard caliche.
On the High Plains, widespread small, intermittent streams dominate the drainage. Pecos River drainage erodes the west-facing escarpment of the Southern High Plains, which terminates against the Edwards Plateau on the south.
The Basin and Range province contains eight mountain peaks that are higher than 8, feet. At 8, feet, Guadalupe Peak is the highest point in Texas.
Mountain ranges generally trend nearly north-south and rise abruptly from barren rocky plains. Plateaus in which the rocks are nearly horizontal and less deformed commonly flank the mountains.
Cores of strongly folded and faulted sedimentary and volcanic rocks or of granite rocks compose the interiors of mountain ranges. Volcanic rocks form many peaks. Large flows of volcanic ash and thick deposits of volcanic debris flank the slopes of most former volcanoes.
Ancient volcanic activity of the Texas Basin and Range province was mostly explosive in nature, like Mount Saint Helens. Volcanoes that poured successive lava flows are uncommon. Eroded craters, where the cores of volcanoes collapsed and subsided, are abundant.
Gray oak pinyon pine alligator juniper parks drape the highest elevations. Creosote bush and lechuguilla shrubs sparsely populate plateaus and intermediate elevations. Tobosa black grama grassland occupies the low basins. The Physiographic Map of Texas is a useful guide to appreciate statewide travel. Texas abounds with vistas of mountains, plateaus, plains, hills, and valleys in which many rock types and geologic structures are exposed.
A variety of vegetation grows, depending on local climate. In river basins of Texas, streams transport a precious resource--surface waters. They contain the essential nutrients for maintaining life in plants, animals, and people. They are the feedstock of nature-forests, prairies, meadows, swamps, and marshes, as well as pastures, and croplands.
All the products that build our communities-concrete, bitumen, bricks, wood, paper, and plastics-require their waters. A river basin is the entire area drained by a stream and its tributaries.
The highest land surrounds the river basin, forming its outside boundary as well as dividing it from adjacent basins. From this boundary, or divide, all water falling into the basin flows downhill to a pour point.
At the pour point, small stream basins spill into larger stream or river basins. The 13 major river basins of Texas vary greatly in size, shape, and stream patterns. Although the river basins share many common features, each is unique. River basins reflect the climate, geology, topography, and vegetation of an area. Five Texas river basins originate outside Texas. The eight other Texas river basins originate within Texas. The Canadian and the Red Rivers have their outlets, or pour points, beyond Texas.
Our remaining 11 river basins spill into the Gulf of Mexico. Only the Rio Grande and the Brazos River discharge directly into the Gulf of Mexico, where they built substantial deltas in the recent past.
The remaining river basins spill into estuaries and bays along the coast. Marshes, seagrasses, shrimp, fish, and bottom fauna such as oysters require the nourishment provided by nutrients contained in the inflow of fresh water and sediments from these rivers. As shown on the table below the map, Texas river basins vary greatly in area and length.
The largest, the Rio Grande, contrasts markedly with the smallest, the San Jacinto River, in both size and length. The Red, Colorado, and Brazos Rivers have similar areas, but the Brazos River is 25 percent longer than the other two.
Most of the river basins have elongated shapes. Poorly drained coastal basins are situated between many of the large river basins. Coastal basins along the Gulf of Mexico contain only small streams, commonly named "bayous," east of the Brazos River. Their small discharges into the bays are estimated, and these basins lack instruments to measure stream flow.
Climate, especially rainfall and evaporation, strongly controls the flows of rivers and streams in Texas. In the Sabine River basin, mean annual rainfall is nearly 60 inches and annual evaporation is less than 70 inches, whereas in the Rio Grande basin, mean annual rainfall ranges from 8 to 20 inches and annual evaporation is as much as inches.
Therefore, East Texas streams flow year round, but most West Texas streams flow only part of the year or intermittently. East of the Trinity and south of the Red Rivers, river basins generally contain dark and murky streams because of high organic content. West of Austin, principal streams in river basins run clear when not in flood.
In East Texas, the flow in basins, which is the volume of water flowing past a point per unit of time, remains relatively constant. In west and north Texas, flow changes rapidly from none or dry to flood stage following storms; consequently these intermittent streams are called "flashy.
We take advantage of the climatic effects on basin streams in selecting where we build reservoirs, as shown in the table on the River Basin Map of Texas. The largest reservoir is Toledo Bend in the Sabine River Basin, which has a storage capacity of 4,, acre-feet. One acre-foot is the amount of water it takes to cover 1 acre of land 1 foot deep.
The smallest reservoir, which is far to the west, is the Mackenzie Reservoir of the Red River, holding 46, acre-feet. River basins strongly reflect their geology. For example, in wetter East Texas where uncemented sands and muds dominate the terrain, river valleys are wider and contain broadly meandering streams carrying abundant suspended brown mud. Meanders are the large snakelike bends that migrate back and forth across the floodplain over time.
Eastern stream bars are composed of fine sands, silts, and clays. East Texas rivers have gentle mean gradients of 1. In contrast, far West Texas streams cut deep gorges with nearly vertical canyon walls into bard limestones and sandstones. There stream courses are incised and normally flow quite clear. Western stream bars have larger proportions of gravel and coarse sand components. Western rivers have steeper mean gradients of 7. Bedrocks, the sources of sediments transported by streams, contribute to the stream character.
The Red River gets its name from the red sediment it erodes from red Permian strata. These same Permian strata contain thick salt beds that dissolve into waters of the Canadian and upper Brazos Rivers, making them too salty to drink.
Black rocks that come from volcanic lavas are especially common in the Rio Grande gravels. These gravels also contain many rock types transported from New Mexico, like granites.
In terrains where river basins cross adjacent hard and soft rocks, stream patterns and gradients reflect the differences in erosion resistance. Waterfalls commonly increase flow rates, dropping over hard resistant rocks onto soft rocks. Pedernales Falls State Park contains a good example. In gently sloping hard and soft rock formations, streams flow in valleys preferentially eroded into soft rocks; they rarely erode through the harder rocks. Geologic structures commonly control the directions, patterns, and local gradients of streams.
Streams typically occupy areas of easily eroded, highly fractured bedrocks. Fault- and fracture-controlled drainage is common throughout the state. River basins commonly align parallel to faults and fractures and then abruptly bend at high angles, forming kinks controlled by intersections of structures.
In East Texas, salt domes near the land surface cause streams to curve around them. No Texas river basin is in a natural state along its entire length. All are somewhere impacted by humans and have dams, levees or engineered channels, and wastewater treatment plants.
Texas rivers quench our thirst, carve a magnificent scenery, provide recreation, create habitats for wildlife, and supply water for agriculture and industry.
As the population of Texas increases, we must continue to guard the availability and quality of these assets and wisely allocate our water resources. Aquifers are a critical part of the water cycle. Rainwater that falls on land can 1 evaporate, 2 be taken up by plants, 3 run off into streams, or 4 seep underground through soil, sediment, and rocks.
The fraction of the water that moves into the groundwater is called recharge. Rock or sediment that stores and transports water underground in amounts and quality sufficient to be useful to humans is called an aquifer.
Water is stored in spaces within the sediment or rock that are called pores. Pores range from microscopic spaces between mineral grains, to fractures, to caves. Below the water table, most pores in a rock are filled with water, so this rock is described as saturated. The aquifer property that lets water move through connected pores is known as permeability.
Gravel, sand, and sandstone are sediment and rock types that are commonly very permeable. Clay and shale are examples of sediments and rocks having small or poorly connected pores through which water does not move easily.
The permeability of limestone and igneous rocks depends on the geologic history of the rock. Water in an aquifer is not stagnant but instead moves under pressure. It enters the aquifer at the surface in the recharge zone. Water leaves the aquifer at discharge areas. These can be springs or wells or areas along the bed of a river or along the coast. The flow path from the recharge area to the discharge area can be short and simple, or it can be hundreds of miles long and take fresh water to depths of several thousand feet before bringing it back to the surface.
Some parts of the flow path have a low-permeability layer above the aquifer, which is called the confined part of the aquifer. When a well is drilled into a confined aquifer, pressure in the aquifer will make water rise in the well.
If pressure in the confined aquifer makes the water in the well rise above the land surface, the well is a flowing artesian well. Water is pumped from wells for irrigation, city and home water supplies, manufacturing, and mining activities.
Groundwater dissolves or chemically interacts with minerals in the rock. What we call fresh water contains less than 1, milligrams of dissolved material in each liter of water.
In a limestone aquifer, water dissolves some of the mineral calcite, which gives water the taste and poor lathering properties of hard water. At greater depths and in less-permeable rocks, water becomes increasingly salty. It also becomes saline where it comes in contact with salt deposits and where, in arid areas, evaporation of groundwater concentrates dissolved minerals.
People can alter the natural system. If water removed from the aquifer exceeds the water replaced by recharge, springs may dry up, salt water may move into an area that previously had fresh water, or the ground surface may subside, increasing the risk of flooding.
Spilling or misuse of materials such as salt water, oil, chemicals, pesticide, or fertilizer can contaminate groundwater. Texas gets more than half its water supply, more than 2.
Because each aquifer system in Texas is unique, this map captures only the general distribution of major and some minor aquifers. The nine major aquifers in Texas supply more than 90 percent of the state's groundwater. Some of the most productive aquifers in the state are in relatively young to 1.
The Brazos River alluvium aquifer, for example, was formed when sand, gravel, silt, and clay were deposited in the floodplain and channel of the ancient Brazos River. Alluvial aquifers along many Texas rivers are used for domestic water supply and for irrigation. Natural and human sources of salinity have reduced the water quality in some alluvial aquifers, such as the Lipan aquifer.
Another group of aquifers are formed in deposits associated with rivers that flowed during the Cenozoic as much as 65 mya. The Seymour aquifer is hosted by sand and gravel deposits of ancient east-flowing rivers. Its age is indicated by the valleys that modern rivers have cut into these deposits. Sand dunes as well as river sediment contributed to the Pecos River alluvium, and older rocks Rustler beneath the Pecos alluvium exchange water with it.
The most prolific aquifer in Texas, the Ogallala aquifer of the Southern High Plains, is Cenozoic sands and gravels that were also deposited in a river-system complex.
This aquifer is recharged from small playa lakes on the High Plains surface and is used heavily for irrigation. Is there a marathon in Austin today? The Austin Marathon, Half Marathon and 5K has a rich history, going back to , and is now one of the largest marathons in the country. Where does the Austin Marathon start? The Start Line is located in downtown Austin.
What time does the Austin Marathon end? Athletes will be notified of event changes via email and social media. The Official Austin Marathon event mobile app will be released before the event date. What is the second highest point in Texas? Guadalupe Mountains.
How flat is Dallas? Dallas and its surrounding area are mostly flat; the city lies at elevations ranging from to feet to m above sea level. What is the flattest state? Which states have no mountains? Is Texas a desert state? Although Texas is popularly associated with the U. Most of the population centers are in areas of former prairies, grasslands, forests, and the coastline.
Veterans Support The Veterans Services and Supports Project will assist local veterans and their families in accessing resources available within the community including food, housing, counseling, health care, job searches, etc. Helpful Links Here you will find some helpful links that should be useful for finding local, state, federal and non-profit assistance for behavioral health, developmental health, substance abuse and developmental disabilities.
Main Location. Aransas County. Concho Rockport, Texas Bee County. Brooks County. Potts Falfurrias Texas Jim Wells County - Alice.
Front Street Alice, Texas Duval County. San Patricio County - Taft. Taft, TX George West Annex Office. Kenedy - Kleberg Counties. Donations Coastal Plains Community Center accepts donations to assist those in need.
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