Technical and Special Reports
These technical and special reports contain the results of TWRI-funded research.
Recent Submissions
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Thompson, William (Texas Water Resources Institute, July 2008)[more][less]
Abstract: This report presents the results for Subtask 1.7 of the Pecos River Basin Assessment project sponsored by the U.S. Environmental Protection Agency (EPA) and the Texas State Soil and Water Conservation Board (TSSWCB). The original objective of Subtask 1.7 was to measure the economic impact of Tamarix spp. (saltcedar) control along the Texas portion of the Pecos River. As work progressed on other hydrologic studies associated with this project, the scope of the project shifted to analyze the expected economic impacts of implementing potential salinity control measures on the Pecos River above Red Bluff Reservoir to decrease salinity levels in water used for irrigation in Texas. Scenarios evaluated quantified the economic impact of improving water quality used by Texas irrigators to the level of water utilized by the Carlsbad Irrigation District in southern New Mexico. The purpose for this evaluation was to see if the overall economic impact of producing less salt tolerant, more profitable crops might be significant enough to encourage producers to convert current cropping practices to more profitable practices not currently useable due to elevated irrigation water salinity levels. Between 1970-2005, irrigation storage and delivery data from the Red Bluff Water Power Control District (RBWPCD) were analyzed and water delivery from the year 2005 was used as a representative level of available irrigation water. Estimates of current cropping patterns for the irrigated lands within the seven sub-districts of the RBWPCD were established. Data were collected and reviewed for the Carlsbad Irrigation District of New Mexico, just up stream from Red Bluff Reservoir, to establish two estimated alternative cropping patterns under a reduced salinity environment. The differences in the value of farm production between the baseline scenario and the two alternative cropping patterns were entered into the Impact Analysis for Planning (IMPLAN) input-output model of the six county upper Pecos River Basin to quantify the general economic impact to the local economy as a result of changes in current cropping practices. As compared to the typical cropping practices, Alternative 1 reduces the more salt tolerant cotton acreage and moderately tolerant wheat acreage while increasing the acreage of moderately salt sensitive alfalfa. The direct output effect for this alternative cropping pattern was $1,446,206; an increase of 120 percent over the current typical cropping system. The total economic impact to the local economy was $2,807,166 with a net creation of 1.17 full time employee (FTE) jobs. This scenario did not incorporate the impacts to local cotton gins and as a result may be a less desirable option. Alternative 2 maintains cotton acreage, reduces wheat acres, and increases alfalfa acres as compared to typical practices. Compared to Alternative 1, this scenario models one-third of the alfalfa acreage, 5.5 times more acres cotton and equal amounts of wheat. The direct output effect for this alternative cropping pattern was $815,378; an increase of 130 percent over the current typical cropping system. The total economic impact was $1,588,795, and will generate a net increase of 7.8 FTE jobs. 2 The combined effective delivery losses of the Pecos River channel and the sub-district delivery infrastructure have averaged 55.5 percent since 1970. Uncertainty stemming from weather patterns, annual irrigation water availability, and the delivery losses of the current system complicate planning and deter investments by both farmers and irrigation districts making a large-scale conversion from current cropping practices to potentially more profitable practices less likely. In order to increase the likelihood of cropping changes and promote future irrigated agriculture in the basin, a new study of the infrastructure improvements for the RBWPCD and the 7 sub-districts is needed; this was last done in 1991. This study did not measure the impact of increasing available water supplies because it is outside the revised scope of the project and is furthermore an unlikely scenario given the region’s climate. Tremendous increases in grain prices, fuel, and fertilizer costs in recent months can potentially alter economic impacts predicted by this study; these dramatic changes have likely changed demand and production functions of several industries. An updated analysis is needed to better quantify potential economic impacts under the current economic situation. The primary focus of this analysis has been on irrigated farm production; however, the initial intent was to evaluate the economic impacts of saltcedar control in the riparian corridor in general. A large majority of lands in the riparian corridor and watershed are classified as rangelands; which can have a significant impact on the watershed’s economy. Results of a survey of landowners/managers along the Pecos River can be found in appendix 2. This survey was conducted to quantify economic impacts realized by landowners along the river as a result of saltcedar treatment along the river. Generally speaking, these landowners/operators have had little economic benefit or value from the treatment of saltcedar along the Pecos River. URI: http://handle.tamu.edu/1969.1/88062 Files in this item: 1
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Mukhtar, Saqib; Gregory, Lucas; Wagner, Kevin (Texas Water Resources Institute, January 2009)[more][less]
Abstract: Two upper North Bosque River segments were designated as impaired in 1998 due to point source and nonpoint source (NPS) pollution of phosphorus (P) to these segments in the watershed. As a result, two Total Maximum Daily Loads (TMDLs) were applied which called for the reduction of annual loading and annual average soluble reactive P (SRP) concentrations by an average of 50%. This demonstration was conducted to evaluate the efficacy of a prospective new technology, an Electrocoagulation (EC) system, to potentially aid the dairy farmers in meeting the goals set by the TMDLs. This EC system used chemical pre-treatment to coagulate and separate solids in slurry pumped from the dairy lagoon, the liquid then flowed over charged iron electrodes giving off ions that cause coagulation and precipitation of P and other metals. The configuration of the system and its components varied from event to event. To accommodate these changes, the points at which samples were taken varied as well. At all sampling events, samples were taken from the lagoon effluent, the lagoon effluent after the addition of the chemical pre-treatments, the effluent from the EC system and the residual solids. Samples were also taken where the mixture exited the centrifuge after it was added to aid in removing solids. These samples were sent to the lab where they were analyzed for solids, nutrients, metals, pH, and conductivity. In order for the EC unit to function properly, the technology provider removed large amounts of solids from the raw lagoon effluent even though its solid concentration was a low 0.6 mg/L. By the time the treated effluent reached the EC unit, concentrations of many analytes were so low it is hard to conclude whether or not it is an effective component for treating dairy lagoon effluent. Samples of effluent from the centrifuge indicated that it was the most efficient component in the system as it removed larger amounts of solids, as well as more of the nutrients and metals than any other component in the system. Overall, the performance of the system was sporadic from event to event, which may be attributed to the changes in the system that occurred. However, it was consistently effective in reducing total phosphorus (TP) and SRP, on average reducing these constituents by 96% and 99.6% respectively from the dairy lagoon effluent. Some uncertainty surrounds the efficacy of this system to reduce both TP and SRP so efficiently because both these and other nutrients are not stable and do change form. Economic data shows that costs to treat dairy lagoon effluent were $0.12 per gallon ($120 per 1,000 gallons). This cost did not include removal of residual material from the farm and will vary depending on the number of cows and volume of process generated influent entering the lagoon. This price per gallon is considerably higher than traditional methods of sludge treatment that range from $5 to $32 per 1,000 gallons of treated effluent. URI: http://handle.tamu.edu/1969.1/86146 Files in this item: 1
TR 346 ECFinalReport_2006-08-04.pdf (742.5Kb) -
Mukhtar, Saqib; Wagner, Kevin; Gregory, Lucas (Texas Water Resources Institute, January 2009)[more][less]
Abstract: Two upper North Bosque River segments were designated as impaired in 1998 due to point source and nonpoint source (NPS) pollution of phosphorus (P) to these segments in the watershed. As a result, two Total Maximum Daily Loads (TMDLs) were applied which called for the reduction of annual loading and annual average soluble reactive P (SRP) concentrations by about 50%. This demonstration was conducted to evaluate the efficacy of a prospective new technology, the Geotube® dewatering system that may aid dairy farmers in reducing P from lagoon effluent to be applied to waste application fields and thus reducing NPS pollution. In this Geotube® dewatering system, effluent is pumped from the dairy lagoon using a PTO-driven chopper pump into a PVC pipe with a series of elbows that facilitate thorough mixing of the chemical pretreatment. Alum and a polymer are added to the effluent agglomerate solids and precipitate P as it flows through the elbows to the Geotubes®. Two 14’ x 50’ geotextile fabric tubes were installed on a 6 millimeter impermeable polyethylene sheet next to a primarily dairy lagoon that received flushed manure. After the tubes were filled, they were allowed to dewater for a period of 6 months. Rainwater typically sheds off of the tubes and does not soak into the tubes. At the first two sampling events in March and April 2005, samples of the dairy lagoon effluent, the lagoon effluent after the addition of the chemical pre-treatment, and the effluent dewatering from the tubes were taken and flow rates into the tube were measured. At the last sampling event in October 2005, samples of residuals and depth of the dewatered residuals were taken from both tubes. Samples from the three events were analyzed for concentration of solids, nutrients, metals and pH. Results showed that the Geotube® dewatering system performed very well in filtering solids from the dairy lagoon effluent, removing an average of 93.5% of the total solids between the two pumping and dewatering events of March and April. It was effective in removing nutrients and metals as well. The average percent reduction of SRP for the two events was very high at 85%. It should be noted that these findings were limited to the sampling of the tubes in March and April and the tubes continued to dewater for several months. Therefore, any changes in the concentration of the dewatering effluent, volatilizing solids and precipitating substances after the sampling events could not be accounted for. A brief economic analysis of this dewatering system was furnished by the technology provider. Cost estimates for a long-term dewatering system were $90,000 to treat 1.9 million gallons of dairy lagoon effluent containing 15+ years worth of nutrients and solids that settled to the bottom of the lagoon at a 2000 head lactating cow open-lot dairy. This estimate includes all capital and operating costs except removal of residual solids. Costs will vary depending on the size of the dairy and the length of time between lagoon treatments using Geotubes®. URI: http://handle.tamu.edu/1969.1/86145 Files in this item: 1
TR-345 GTFinalReport_2006-08-04.pdf (710.1Kb) -
Rahman, S.; Mukthar, S.; Gregory, L. (Texas Water Resources Institute, January 2009)[more][less]
Abstract: Two upper North Bosque River segments were designated as impaired in 1998 due to point source and nonpoint source (NPS) pollution of phosphorus (P) to these segments of the watershed. As a result, two Total Maximum Daily Loads (TMDLs) were applied which called for the reduction of annual loading and annual average soluble reactive P (SRP) concentrations by about 50%. Under Clean Water Act (Section 319(h)), a new technologies demonstration project was funded by the USEPA Region 6 and administered by the Texas State Soil and Water Conservation Board (TSSWCB) for reducing water pollution associated with dairy animal production systems. As part of this demonstration, the efficacy of a prospective new technology (i.e.L4DB® microbial treatment system) was evaluated, which may aid dairy farmers in reducing P from lagoon effluent. In many cases, this effluent is applied to waste application fields (WAFs) as irrigation water; thus reducing P in the effluent can have a direct impact on NPS pollution in the watershed. Beginning in May 2006 a dairy’s anaerobic lagoon was treated with L4DB® microbes at an average application rate of 65 gallons (246 L) of microbial solution/month for a period of 12 months. Lagoon samples were collected monthly or bi-monthly from two different profiles: lagoon supernatant (LS, sampled from top of the liquid level to 2ft (61 cm) depth) and lagoon profile (LP, sampled from the entire depth of the lagoon) using a sludge judge (a sampling tube with a check valve at the bottom to take lagoon sample at different depths). For each LP and LS, 30 samples (3 samples per location × 10 locations) were collected during each sampling event. A set of 15 LP and 15 LS samples were mixed separately to get two composites of each for nutrients including P, solids, pH, conductivity and metals. In addition, 60 samples of lagoon effluent (hereafter IR) used to irrigate a nearby pasture were collected bi-monthly from a riser located just upstream from the big gun irrigation unit. Fifteen IR subsamples were grouped together to get four IR composite samples. The IR composite samples were also analyzed for the above mentioned physical and chemical constituents. L4DB® microbial treatment reduced average sludge depth by 24% as compared to its pre-treatment level (however, this reduction was 16%, when sludge measurement anomaly in August 2006 was excluded). The microbial treatment also reduced averaged total solids (TS) and total suspended solids (TSS) by 43 and 45%, respectively, for the LP, and 60 and 71%, respectively, for LS. Conversely, these values increased by 124% for IR effluent over times. This microbial treatment system was effective in reducing average total phosphorus (TP) by 27 and 52% for the LP and LS, respectively, but not effective in reducing TP concentration for IR effluent. Overall, no clear soluble reactive phosphorus (SRP) reduction trends were observed for any sampling locations. Similar to the effect on TP, the L4DB® treatment was effective in reducing total Kjeldahl nitrogen (TKN) from the LP (36%) and LS (48%), but not effective in reducing potassium (K) for LP and LS. No clear trend of reducing these nutrients from IR effluent was observed over time. This microbial treatment system was effective in reducing metals concentration as well. The average concentration reductions of Al, Ca, Cu, Fe, and Mn for LP were over 50%, while the reduction seen in Mg was only 22%. Similarly, the concentration reductions observed in LS samples were over 60% for the same suite of elements while Mg was reduced by about 42%. No clear metal concentration reduction trends were observed for IR effluent. As a result, it can be inferred that most of these solids, nutrients, and metal reductions were likely due to microbial treatment, dilution of lagoon slurry by excessive rain and runoff as well as settling of dead and degraded bacterial mass accumulated at the bottom of lagoon. Additional measurements of lagoon sludge accumulation rate and constituents are warranted to assess possible increase in nutrients and solids due to accelerated solids settling and increased accumulation of microbial mass at the lagoon bottom. URI: http://handle.tamu.edu/1969.1/86144 Files in this item: 1
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Provin, T.; Mukhtar, S.; Munster, C.; Vietor, D.; Tahboub, M.; Schnell, R. (Texas Water Resources Institute, January 2009)[more][less]
Abstract: Polymer – Abbreviation for polyacrylamide is used in water purification to flocculate suspended organic matter. Although polyacrylamide is designated as a non-toxic additive by USDA, its building block, acrylamide, is a potential nerve toxin in humans and causes birth defects and cancer in animals. A concentration limit of 500 ppm acrylamide in polyacrylamide preparations has been established for water treatment applications. Geotube® solids – particulate matter collected from wastewater pumped from lagoon into semi-permeable fibrous sock. Lysimeter – Container in which the volume of soil used to grow plants is isolated hydrologically from surrounding soil to control and measure water and nutrient inputs and losses. Mineralization – Conversion of organic N to NH4+. Heterotrophic microorganisms use organic carbon compounds as an energy source for the conversion process. URI: http://handle.tamu.edu/1969.1/86143 Files in this item: 1
TR-343 Turfgrass Demo 1.9.09.pdf (381.7Kb)
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