Browsing Texas A&M AgriLife Research by Title

Now showing items 1-20 of 1960

129 Iodine: A New Hydrologic Tracer for Aquifer Recharge Conditions Influenced by River Flow Rate and Evapotranspiration

Schwehr, K. A.; Santschi, P. H.; Moran, J. E. (Texas Water Resources Institute, 2003)

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URI: http://hdl.handle.net/1969.1/94982

Files in this item: 1

sr2003-012.pdf (873.8Kb)

The 1997 Irrigation Suspension Program for the Edwards Aquifer: Evaluation and Alternatives

Keplinger, Keith O.; McCarl, Bruce A. (Texas Water Resources Institute, February 1998)

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Abstract:

The EAA implemented a pilot irrigation suspension program in 1997 on 9,669 acres mainly in Medina and Uvalde counties with the objective of increasing springflow at Comal Springs, and providing relief to municipalities in meeting Critical Period (drought) Management Rules. The Aquifer region, however, experienced a wet Spring in 1997, so that even irrigators not enrolled in the program applied little or no irrigation water. If conditions were dry in Spring 1997, aquifer simulation results indicate that suspending irrigation on enrolled acreage would have reduced pumping by 23,206 acre-feet and would have augmented Comal springflow by 6,498 acre-feet during the program year and by 17.7 cfs in August. The level of the eastern portion of the Aquifer would have been expect to rise by about 3.8 feet, and the cost per acre-foot of suspended irrigation would have been about $99. Payments to irrigators totaled $2,350,000. The ISP Program did cause farmer adjustments. Participants in the ISP program planted less corn, cotton, vegetables, and peanuts in favor of more sorghum and wheat. Irrigators who converted to dryland purchased somewhat less fertilizer, seed, and labor, but secondary effects on the local economy appeared to be small. The price paid per suspended acre was much higher than regional lease rates and average cropping profit margins in many instances. Factors which may have accounted for the high bids include: 1) lack of experience with an ISP, 2) its late start up, 3) the belief that bids might affect future water prices or offers, 4) tendencies to bid high enough to cover costs under a worst case scenario of a total loss of dryland crops, 5) collusion and need to bid high enough to compensate all under current land lease arrangements. Bids in future ISP solicitations might be lower, or might not. Given the substantial difference between local irrigated land rental rates and ISP bids, it seems unlikely that the EAA could attract sufficient acreage by capping bids at rental rates. There may be, however, some latitude for the EAA to set a maximum per acre rate somewhere between local rental rates and the ISP bids. This, combined with announcing the program and executing contracts in October or November, has the possibility of substantially reducing program cost. The EAA may also want to consider offering an option contract which when implemented would suspend irrigation in April or May. Waiting until April or May would provide the EAA more information on current year weather allowing better information on whether irrigation suspension is really necessary since: 1) more time would have elapsed allowing administrators to know Aquifer elevation at a later date, and 2) information of weather, irrigation use to date and projected irrigation for the remainder of the cropping year is increased this point. The cost of a single implementation of such a program may be substantially higher than a January 1 contract, since irrigators may sustain greater loss. Expected program cost, however, could be lower, since this option would be exercised less frequently, offsetting over higher cost of implementation. Good alternatives to an ISP are limited. We evaluated the potential of 1) implementing more efficient irrigation technology and 2) buying land and leasing it back during wet or average years. The ISP is a more cost effective source of critical water than is the use of subsidized irrigation efficiency largely because the ISP can put in place only when water is needed. Also, while not considered here, evidence in areas such as the High Plains suggests that irrigator pumping is not reduced by the amount an increase in irrigation efficiency would imply. This is because irrigators may choose to irrigate more water intensive crops and/or irrigate more acreage when efficiency is increased. The high bids experienced in the 1997 program compared to price of land in the Aquifer region suggests that a buy-leaseback arrangement could substantially reduce the cost to the EAA of suspending irrigation. This, of course, would require an alternate set of administrative costs by the EAA and may be less expensive than the ISP. Also the picture may be altered by the adjudication of water rights in the Aquifer which will likely be finished within three to five years. After water rights adjudication, however, buying and leasing back water rights may be a very appropriate and cost effective strategy for the EAA. In sum, we conclude that the 1997 pilot ISP was a reasonable response to the drought condition experienced in 1996. Fine-tuning the selection criteria, bid arrangement, allowing greater lead time, and/or implementing an ISP or option contract later in the year, holds the potential for reducing the cost of program implementation. A land-based ISP is an interim arrangement that can be implemented in the absence of a fully functioning permit system. After water rights are adjudicated in the region, ISP and option contracts will take on more conventional forms involving buy, lease, and option contracts for water rights. It is expected that water-based versus land-based arrangements would likely facilitate the transfer of water at lower rates.

URI:

http://hdl.handle.net/1969.1/6152

Files in this item: 1

tr178.pdf (244.9Kb)

2009 International SWAT Conference Conference Proceedings

Unknown author (Texas Water Resources Institute, August 2009)

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URI: http://hdl.handle.net/1969.1/90520

Files in this item: 1

TR-356 2009 Int ... Conference Proceedings.pdf (17.76Mb)

35 Years of Farming Systems Research in the Texas Blackland.

Hipp, Billy W.; Simpson, Benny J. (Texas Agricultural Experiment Station, 1988)

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Description: 28 pg

URI: http://hdl.handle.net/1969.1/146707

Files in this item: 29

b1604 0001.tif (88.90Mb)
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4-H Cowman.

Thompson, Uel D. (Texas Agricultural Experiment Station, 1966)

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Description: 16 pg

URI: http://hdl.handle.net/1969.1/90556

Files in this item: 17

b1058 0001.tif (89.92Mb)
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4-H Favorite Foods Unit 1.

Cox, Maeona; Mason, Louise; Reasonover, Frances; Tribble, Marie (Texas Agricultural Experiment Station, 1958)

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Description: 28 pg

URI: http://hdl.handle.net/1969.1/86564

Files in this item: 29

b0907 0001.tif (84.27Mb)
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Ability - Not Disability: Clothing.

Anonymous, (Texas Agricultural Experiment Station, 1981)

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Description: 16 pg

URI: http://hdl.handle.net/1969.1/126191

Files in this item: 18

b1255 0001.tif (50618Kb)
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Ability - Not Disability: Grocery Shopping and Food Preparation.

Anonymous, (Texas Agricultural Experiment Station, 1981)

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Description: 20 pg

URI: http://hdl.handle.net/1969.1/126189

Files in this item: 22

b1253 0001.tif (51881Kb)
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Ability - Not Disability: Organizing Housework.

McCormack, Linda J. (Texas Agricultural Experiment Station, 1981)

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Description: 12 pg

URI: http://hdl.handle.net/1969.1/126192

Files in this item: 13

b1259 0001.tif (53.30Mb)
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Ability - Not Disability: Wheelchairs.

Anonymous, (Texas Agricultural Experiment Station, 1981)

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Description: 12 pg

URI: http://hdl.handle.net/1969.1/126190

Files in this item: 14

b1254 0001.tif (52131Kb)
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Abstracts of Bulletins 305 to 327, Inclusive.

Jackson, A. D. (Texas Agricultural Experiment Station, 1926)

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Description: 12 pg

URI: http://hdl.handle.net/1969.1/4005

Files in this item: 13

b0338 0012.tif (6.824Mb)
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Accelerated Wear Tests on Common Floor-covering Materials.

Stewart, B. R.; Kunze, O. R.; Hobgood, Price. (Texas Agricultural Experiment Station, 1958)

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Description: 8 pg

URI: http://hdl.handle.net/1969.1/86537

Files in this item: 9

b0890 0001.tif (12.94Mb)
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Accessories Around the Clock.

Boyles, Rheba Merle; Hard, Graham; Roberson, Nena; Eaton, Fannie Brown (Texas Agricultural Experiment Station, 1958)

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Description: 20 pg

URI: http://hdl.handle.net/1969.1/86557

Files in this item: 21

b0911 0001.tif (86.41Mb)
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Action and Inaction Levels in Pest Management.

Sterling, Winfield (Texas Agricultural Experiment Station, 1984)

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Description: 24 pg

URI: http://hdl.handle.net/1969.1/128868

Files in this item: 25

b1480 0001.tif (87.02Mb)
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Active Phosphoric Acid and Its Relation to the Needs of the Soil for Phosphoric Acid in Pot Experiments.

Fraps, G. S. (George Stronach) (Texas Agricultural Experiment Station, 1909)

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Description: 72 pg

URI: http://hdl.handle.net/1969.1/3455

Files in this item: 73

b0126 0072.tif (6.687Mb)
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The Active Potash of the Soil and Its Relation to Pot Experiments.

Fraps, G. S. (George Stronach) (Texas Agricultural Experiment Station, 1912)

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Description: 39 pg

URI: http://hdl.handle.net/1969.1/3490

Files in this item: 40

b0145 0039.tif (6.701Mb)
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Activities of Livestock on the Range.

Cory, V. L. (Vivian L.) (Texas Agricultural Experiment Station, 1927)

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Description: 47 pg

URI: http://hdl.handle.net/1969.1/86268

Files in this item: 48

b0367 0047.tif (6.892Mb)
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Acute and Genetic Toxicity of Municipal Landfill Leachate

Brown, K.W.; Schrab, G.E.; Donnelly, K.C. (Texas Water Resources Institute, October 1991)

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Abstract:

Municipal solid waste (MSW) landfills have been found to contain many of the same hazardous constituents as found in hazardous waste landfills. Because of the large number of MSW landfills, these sites pose a serious environmental threat to groundwater quality. This study was conducted to assess the environmental hazards that materials leaching from four MSW landfills pose to groundwater supplies. Four leachate and one upgradient groundwater samples were collected from landfills selected to be representative of landfills of differing ages and types of wastes. Each sample was tested through three genetic toxicity bioassays (The Aspergillus diploid assay, the Bacillus DNA repair assay and the Salmonella/microsome assay) to measure the ability of each sample to induce mutations in bacteria, bind to microbial DNA, or cause chromosome damage in diploid fungi. Genetically toxic chemicals may cause cancer, genetic disease, sterility, abortions, heart disease or a variety of other chronic effects. These chronic effects can be subtle and may not appear for decades after exposure. In addition to the three genetic toxicity assays, each sample was tested in the Microtox test to measure acute toxicity. This assay is a measure of the ability of the sample to cause cell death. Organisms exposed to elevated levels of acute toxins may express the toxic effects through organ disfunction or the complete death of the organism. Each sample was chemically analyzed using GC/MS techniques and the chemical concentrations were used to calculate a chemical based risk assessment which is an estimate of the potential carcinogenic health effects associated with the mixture of chemicals in the sample. All four leachate samples exhibited acute toxicity in the Microtox test. Leachate from landfills representative of both an old unlined landfill which received residential waste and a new operating landfill receiving residential waste contained concentrations of some priority pollutants in excess of promulgated standards for drinking water. Chemical based risk assessments for these same two leachates showed them to have mean and 98th percentile cancer risks of 1 in a thousand (10-3) which is greater than both leachate from a Superfund landfill and leachate from the Love Canal landfill. The results of the acute and genetic toxicity bioassays, combined with the chemical analyses and associated cancer risk assessment clearly showed that leachate from municipal solid waste landfills is just as toxic as that which leaches from landfills where residential and hazardous wastes were codisposed.

URI:

http://hdl.handle.net/1969.1/6182

Files in this item: 1

tr153 done.pdf (2.157Mb)

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Description:	28 pg
URI:	http://hdl.handle.net/1969.1/146707

Description:	16 pg
URI:	http://hdl.handle.net/1969.1/90556

Description:	28 pg
URI:	http://hdl.handle.net/1969.1/86564

Description:	16 pg
URI:	http://hdl.handle.net/1969.1/126191

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