Charles D. Manning

Site hosted by Angelfire.com: Build your free website today!

Testing, Testing 1-2-3-4
Charles D. Manning
c.manning
jungleboy@mail.utexas.edu
Dept. of Geography
University of Texas at Austin

Volumetric Depletion of the Woodbine Sandstone Aquifer
Collin County, Texas

The Research Question

The water of the Woodbine aquifer supplies water for agriculture and forurban and suburban development in Collin County, Texas. How has this use altered the aquifer over the past twenty years?

Geology of the Study Area
Geologically speaking, north Texas is a relatively undisturbed straight stratigraphic column. The figure below is a cross-sectional diagram showing the underlying stratigraphy of the study area. The stratigraphy, or the division of the rocks into distinct units, is a time constant column without any major 'interruptions'or erosional events. It contains all of the representative rock units (ortheir age equivalents) known in Texas from the Cretaceous Period which is a unit of time from approximately 65 to 140 million years ago. Beneath the Cretaceous rocks lies a basement of older rocks from the Pennsylvanian and Permian Periods of the Paleozoic Era.

The Woodbine Aquifer

The Woodbine Aquifer is one of several aquifers that underlies north Texas. It is particularly interesting because it underlies both prime agricultural land as well as land that is experiencing rapid suburban development. There was once a great demand put upon the aquifersof the region although the last few decades the area has begun relying on surface water to supply its needs. The North Texas Municipal Water Districtis the region's governing body on water supply affairs, and it oversees the numerous reservoirs built in the area during the last 40 or 50 years.North Texas receives enough precipitation to make surface water supply feasible, as opposed to some parts of the drier west which must rely heavily upon groundwater supplies. Today the Woodbine Aquifer is mainly used by small municipalities, irrigation, and industrial purposes. Heavy pumping for municipal and industrial water supplies in the Sherman-Denison area have led to water-level declines in excess of 100 feet. (Hopkins 1996)The undisturbed (unpumped) potentiometric surface typically parallels the dip direction of the sandstone unit. The Woodbine Sandstone is composed of fine-grained, cross-stratified fluvial sandstone interbedded with overbank deposits of clay and shale. (Hopkins, 1996) The unit dips eastward reaching a depth of 2,500 feet below the land surface while the regional dip is southeastward averaging approximately 35 feet per mile. Near the boundary of fresh to slightly saline water in the eastern portion of the aquifer, the dip of the rock unit increases to 75 feet per mile. The sandstone thickens both downdip and to the northeast achieving thicknesses of approximately 230 feet in the southern extent of the outcrop to 700 feet in the northeast.


Kns - Nacatoch Sand Kne - Neylandville Marl Kmb - Marlbrook Mar l Kpg - Pecan Gap Chalk Ko - Ozan Formation (clay) Kau - Austin Chalk Kef - Eagle Ford Formation(shale) Kwb- Woodbine Formation Kgm - Grayson Marl Kpd - Pawpaw Fm., Weno Limestone,Denton Clay (undifferentiated) Kfd - Fort Worth Limestone and DuckCreekFm. Kki - Kiamichi Formation Kgw - Goodland Limestone andWalnut Clay (undivided) Ka -Antlers Sand

A volumetric comparison using grid files from the 1977 and 1997 datasets .

The volume function uses two grids and estimates the volume between them by subtracting the lower surface from the upper. In this case, the upper surface is the grid created from the 1977 data because it has higher z-axis values (water level elevations); the 1997 grid becomes the lower surface.

Commercial, Residential and Industrial Depletion of the Woodbine Aquifer over the past twenty years has cost North Texas and Collin County

56,230.4-±0.006% acre·ft of Unreplenishable Water From Yearly Totals

Only if rates of consumption are controlled, will the aquifer be able to survive, sustainable development is the key.

Volume Calculation between Woodbine '77 and '97: Worksheet

In 1977, high aquifer levels reflect low depletion. Sub-divisions are still far away. Agriculture depletes, but not at the level of algebraic sub-divisional use.

Water channels indicate future erosional direction of sandstone formation. Current formation can be linked to past and future of Sandstone formation.

In 1997, low aquifer levels reflect high depletion. Subdivisional depletion has compounded agricultural usage and begun to seriously deplete the limited resourse.

Notice lower balcony has begun to erode faster than other sections. This is due to the high gradient of stream flow.
Underground caverns are formed in this fashion. This process can lead to wells becoming inoperable in the eroded areas.
Mother nature once again will equalize the damages of the parasitic human.

	In 1977, high aquifer levels reflect low depletion. Sub-divisions are still far away. Agriculture depletes, but not at the level of algebraic sub-divisional use.
	Water channels indicate future erosional direction of sandstone formation. Current formation can be linked to past and future of Sandstone formation.

	In 1997, low aquifer levels reflect high depletion. Subdivisional depletion has compounded agricultural usage and begun to seriously deplete the limited resourse.
	Notice lower balcony has begun to erode faster than other sections. This is due to the high gradient of stream flow. Underground caverns are formed in this fashion. This process can lead to wells becoming inoperable in the eroded areas. Mother nature once again will equalize the damages of the parasitic human.

Links:
Lance Christian's Project Outline is here
USGS is here
TWDB is here