Browsing Technical and Special Reports by Title

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

Ward, Ruby; Chen, Chi Chung; McCarl, Bruce A.; Keplinger, Keith O. (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)

Acute and Genetic Toxicity of Municipal Landfill Leachate

Donnelly, K.C.; Schrab, G.E.; Brown, K.W. (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)

The Agricultural Benefits of Salinity Control on the Red River of Texas and Oklahoma

Moore, D. S.; Lacewell, R. D.; Laughlin, D. H. (Texas Water Resources Institute, December 1980)

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Abstract:

Salinity of the waters from the Red River and its major tributaries has virtually eliminated its use for irrigation of agricultural crops in Texas and Oklahoma. A chloride control project has been proposed whereby the source salt waters will be captured and diverted to storage facilities. The purpose of this study was to estimate the net direct benefits to agricultural producers attributable to the proposed salinity control project. Further, estimates of project costs, municipal and industrial benefits and benefits from improving the water in Lake Kemp were obtained to complete a benefit-cost analysis. The procedure used to estimate agricultural benefits was to use a FORTRAN program to develop initial tableaus of a recursive linear programming model representing agricultural production in the study area. Alternative scenarios involving profit maximizing behavior on the part of producers, current cropping patterns, and with and without SAR crop yield effects were developed to provide a range of benefit estimates. The basis for benefit evaluation was to use parameters prescribed by the U.S. Water Resources Council's Principles and Standards and recent proposed changes along with those developed in this study to estimate the increase in net returns to producers in the study area between a with project and a without project condition for a 100 year period of analysis. Benefits were discounted to their present value with discount rates of 7 1/8 percent and 3 1/4 percent for comparative purposes. Benefits estimated herein were used in conjunction with external estimates of project costs and other benefits to evaluate the economic feasibility of the salinity control project. In all scenarios considered, cotton emerged as the major irrigated X crop. Scenarios involving profit maximizing behavior on the part of producers resulted in benefit estimates of over $65 million and $117 million without and with SAR crop yield effects, respectively, at the 7 1/8 percent discount rate. Under a constrained profit maximization scenario where SAR crop yield effects were included and in which producers were assumed to keep current cropping patterns in 1990, adjust to 50 percent of the optimal land use in 2000, and were fully adjusted to optimal land use by 2010, resulted in agricultural benefit estimates of over $87 million at the 7 1/8 percent discount rate. In a scenario where producers were assumed to maintain current cropping patterns throughout the 100 year period of analysis, benefits were estimated to be $28.8 million and $35.8 million without and with SAR crop yield effects, respectively, at the 7 1/8 percent discount rate. Benefit-cost analysis performed in this study indicated that the proposed project was economically feasible under assumptions of all scenarios considered except where current cropping patterns were followed for the entire analysis period. B/C ratios of 1.068 and 1.291 resulted for the profit maximization scenarios without and with SAR crop yield effects, respectively. Where benefits from the constrained scenario were included in the benefit-cost analysis, a B/C ratio of 1.162 resulted. Finally, with current cropping patterns maintained through 2090, B/C ratio estimates Of .907 and .938 resulted without and with SAR crop yield effects included, respectively.

URI:

http://hdl.handle.net/1969.1/6270

Files in this item: 1

tr112.pdf (5.298Mb)

An Analysis of the Effects of Sociodemographic Factors on Daily Per Capita Residential Water Use in Texas Cities

Parpia, Banoo; Bachman, Kenneth; Hamm, Rita R.; Albrecht, Don E.; Murdock, Steve H. (Texas Water Resources Institute, February 1988)

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Abstract:

Water is a key resource of concern to residents and decision makers in the State of Texas and in many other parts of the United States. Careful planning for its use is of utmost importance for the State and the Nation. Such planning requires careful consideration of numerous factors including hydrologic and physiographic factors, engineering feasibility and economic feasibility. At the same time, it is increasingly evident that water needs are closely tied to population growth and to the social, economic and demographic characteristics of the population (Murdock et al., 1985). Thus, attempts to plan for the use of water resources have become increasingly inclusive of socioeconomic as well as physical variables as the costs of incorrectly projecting water demand and misallocating funds for facility construction and management have become apparent (Stees et al., 1976; McFarland and Hyatt, 1973; Reid, 1971; Texas Department of Water Resources, 1984). To date, however, water-related socioeconomic research has concentrated on: 1. water use policy and water use planning 2. the demographic and social correlates of water and other resource use 3. the effects of water use and availability on demographic and social patterns 4. methodologies for projecting demands for resources and the implications of the use of resources An extensive body of research addresses both the need for, and the dimensions that must be considered in, water use policy formation and planning (Markusen, 1978; U.S. Water Resources Council, 1978; Council for Agriculture Science and Technology, 1982; National Water Commission, 1973; Office of Technology Assessment, 1983; Texas Department of Water Resources, 1984). Such analyses persuasively argue for the use of comprehensive, multidisciplinary planning formats, but as several recent reviews of water resources research efforts have noted (Francis, 1982; Napier et al., 1983), much of the basic research necessary to establish the relationships that should form the bases of the information used in such planning has not been completed. The demographic and social correlates of water use have not been sufficiently established. Although total population and demographic structure characteristics are often used in projecting demands for water resources (Mercer and Morgan, 1978; Texas Department of Water Resources, 1984), several recent efforts evaluating the use of demographic and social variables in water use planning have noted that few of the relationships between demographic and social factors and water use have been established empirically (Murdock et al., 1985; Korsching and Nowak, 1983; Francis, 1982). Thus, it is unclear what effects differences in household or family composition patterns or the age structure of a population have on usage of water and related resources. In like manner, although given some attention in the literature (Larson and Hudson, 1951; Bogue, 1963; Kubat et al., 1968; Francis, 1982; Napier et al., 1983), the relationships between such crucial social variables as socioeconomic status, ethnic status and perceptions of water conservation requirements and water use have not been adequately examined. Since other resource uses, such as energy use (Morrison, 1976), show substantial variation across demographic, social and cultural variables, similar effects are likely to be found between demographic, social and cultural variables and water use. The effects of water use and availability on population and social patterns have been given considerable attention (Williford et al., 1976; Doeksen and Pierce, 1976; Albrecht et al., 1984; Murdock et al., 1984; Albrecht and Hurdock, 1985). Such analyses suggest that changes in water resource availability or in the use of water-related forms of technology may lead to substantial changes in the population bases of areas (Albrecht and Murdock, 1985; Fitzsimmons and Salama, 1977) and may lead to related economic and community service changes (Williford et al., 1976). However, such analyses have tended to use only general and very unrefined assumptions concerning the relationships between water availability, use and technology and demographic and social factors. An extensive body of research has also developed related to the modeling of economic and demographic factors associated with resource use and development (Leistritz and Murdock, 1981; Murdock and Leistritz, 1980; Ford, 1976; Stenehjem and Metzger, 1976; Dunn and Larson, 1963; Nercer and Morgan, 1978). Although such models have become increasingly complex, several recent reviews of these models suggest that validation of the parameter assumptions underlying them is needed (Leistritz and Murdock, 1981; Markusen, 1978). In particular, most such models project water demand and use on the basis of per capita or per population unit factors. Population composition is not taken into account. Overall, then, although a few studies have attempted to include demographic variables--age, household size and patterns, race/ethnicity-and social, cultural and behavioral variables--such as water use preferences and cultural patterns of water use--in planning and projection efforts (Kubat et al., 1968; Dunn and Larson, 1963; Korsching and Nowak, 1983; Portney, 1982), water planning and analyses efforts have largely ignored the effects of demographic factors (other than total population size) and social factors in planning for water use and facility construction. Such neglect is particularly unfortunate in states, such as Texas, where populations display wide demographic and social diversity (Skrabanek et al., 1985) and where per capita water use varies widely from one area to another (Texas Department of Water Resources, 1984). Only if analyses of the relationships between demographic and social variables and water use and demand are completed, will it be possible to adequately employ such variables in projections of water demand. Because the inclusion of such variables in projection models should increase the accuracy of projections and improve our understanding of the numerous factors that determine patterns of water use, studies of the effects of demographic and social factors on water use and on projections of water demand deserve additional consideration. This report presents the results of one such study sponsored by the Texas Water Resources Institute. The study has two major objectives: 1. to determine the relationships between key demographic, social and cultural variables and water use in Texas 2. to analyze the implications of the relationships between demographic, social and cultural variables and water use and demand for projections of water use and demand in Texas Specifically, this report presents the results of an analysis of secondary and primary data in which the relationships between water use and other sociodemographic variables are examined, and it reports the effects of using sociodemographic characteristics to project water use. These relationships are of intrinsic interest to professionals involved in water planning and policy formulation, and the results will hopefully be of utility to a wide range of policy and decision makers. The report is organized into five sections. Section I describes the data and methodologies employed in the analysis. Section II presents and discusses the results of the secondary analysis. Section III examines the results of our analysis of survey data from over 800 respondents from 8 communities selected from across the State of Texas. Section IV describes the implications of using demographic and social factors in projecting water use. The final section, Section V, presents generalizations regarding the overall effects of demographic and social factors on water use and demand ant presents our preliminary recommendations regarding the use of such variables in formulating water use and demand projections. Throughout the report, it should be recognized that the fact that the study is limited to one period of time and to only selected areas of the Stste, clearly limits the ability to formulate generalizations that have statewide applicability. The fact that the study is limited in several regards must be recognized.

URI:

http://hdl.handle.net/1969.1/6186

Files in this item: 1

tr143.pdf (2.814Mb)

Arsenate and Arsenite Retention and Release in Oxide and Sulfide Dominated Systems

Wang, Jianlin; Raven, Klaus; Jain, Amita; Loeppert, Richard H. (Texas Water Resources Institute, June 1997)

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Abstract:

Metal pollution of surface water resources in Texas is a significant problem, and is caused by the inflow of sediments from oil fields, old mines and industrial sites, and by the discharge of metal contaminated sewage and industrial effluents. In the preliminary phases of this project we were interested in a range of contaminant metals; however, following early experiments it was determined that emphasis would be given to arsenic due to the importance of several arsenic contaminated sites in east and central Texas. Three important general field and laboratory observations have been made concerning arsenic and have served as a basis for these studies: (1) correlations between metal concentrations of suspended solids or sediments (as measured by the recommended EPA and USGS methods) and metal levels in fish are often poor, (2) metal concentrations in pore waters of bottom sediments are often highly variable (with time and space) and often considerably higher (but sometimes lower) than in the overlying water column, (3) arsenic speciation and solubility are strongly influenced by redox potential. Existing EPA and USGS methods for quantifying the arsenic level of sediment or suspended solids primarily involve digestion by strong acids. While these methods do provide an indication of total concentration of metals, they often do not provide a reliable measure of bioavailability, either directly to aqueous animals or indirectly through the food chain. Inorganic arsenic exists primarily in the +3 or +5 oxidation states (depending on redox potential), and its reactions in soils and sediments are influenced by pH, redox potential, dissolved organic or inorganic components, and sediment colloids (especially Fe sulfides and Fe, Mn, and Al oxides and hydroxides) and organic matter. Arsenic is often concentrated at the surfaces of suspended and sediment colloids (as surface adsorbed and occluded species or possibly as poorly ordered solid solutions). Arsenic (+3 and +5) is bound, by ligand bonding mechanisms, at the surfaces of solid phase Fe, Al and Mn oxides, though there are major descrepencies in the literature concerning the relative bonding strengths of arsenate and arsenite. These reactions at colloidal surfaces strongly influence its availability within the biosphere in oxidized systems. Arsenic (+3) is readily precipitated as As2S3 or coprecipitated in the FeS2 or FeS structure, and these compounds often control the solubility of arsenic in low redox environments. Because of these reactions, arsenic is likely strongly influenced by the presence of inorganic sulfur. The objectives of the study were as follows: 1. To characterize the concentrations and chemical forms of arsenic and the factors which influence its retention and release 2. To evaluate the role of the periodic oxidation/reduction processes that may occur in sediments on retention and release of arsenic 3. To evaluate the probable role of biologically induced processes (e.g., oxidation/reduction, acidification, and ligand exchange) which may influence the mobilization of precipitated or adsorbed arsenic 4. To develop surface dissolution procedures to assess heavy metal mobilization potential in sediments in the aquatic environment, with emphasis on calcareous stream bed sediments. The primary benefit of this study will be to improve procedures for assessing the bioavailability and potential biological hazard of metals in suspended solids and sediments. Accomplishment of these objectives has enabled us to recommend procedures for assessing biohazard potential and ultimately to better monitor aquatic environments.

URI:

http://hdl.handle.net/1969.1/6154

Files in this item: 1

tr176.pdf (30.20Kb)

Assessment of Stormflow and Water Quality from Undisturbed and Site Prepared Forest Land in East Texas (Final Report)

Weichert, A. T.; Crawley, W. W.; Nieber, J. L.; Blackburn, W. H.; DeHaven, M. G. (Texas Water Resources Institute, January 1983)

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Abstract:

In 1979, nine small forested watersheds were instrumented in East Texas to determine the effect of intensive forest management practices On water quantity and quality. Three replications of three treatments were used: 1) clearcutting - followed by shearing and windrowing, 2) clearcutting - followed by roller chopping and 3) undisturbed control. Following treatment, the sheared and windrowed sites exposed 57% of the surface soil compared to 16% for the chopped watersheds. During 1981, the first year after treatment, stormflow volumes increased with the intensity of the site disturbance. Sites sheared produced the greatest amount of stormflow (5.76 inches), followed by chopped (3.26 inches) and the undisturbed watersheds (1.03 inches). Stormflow volumes decreased 66% and 57% on the sheared and chopped watersheds the second year following treatment. Sediment losses were significantly higher on the sheared watersheds (2,620 lb/acre) than the chopped (22 lb/acre), during 1981. By the fall of 1982, the exposure of mineral soil on the sheared sites dropped to 20% and to 4% on the chopped sites. For this reason and the lower volume of runoff, sediment loss for 1982 dropped to 71.3, 4.9 and 4.5 lb/acre for the sheared, chopped and undisturbed watersheds, respectively. Nitrate concentrations were significantly different between treatments during 1981: Sheared - 205 ppb, chopped - 96 ppb and control 10 ppb. During 1982, although nitrate concentrations were lower, the sheared watershed still had a significantly higher concentration. Total nitrogen concentration on the sheared sites was 2,155 ppb, which was significantly higher than the chopped (999 ppb) or the control sites (996 ppb) for 1981. The first year total nitrogen export from the sheared sites (2.79 lb/acre) was 3.5 times greater than the chopped loss (0.76 lb/acre) and 12 times greater than the loss on the control sites (0.24 lb/acre). The second year following treatment, total nitrogen concentrations were not significantly different and total nitrogen loss on the sheared areas was less than half of the loss recorded from the control sites during 1981. Total phosphorus concentrations for 1981 were 221, 85 and 54 ppb for the sheared, chopped and control watersheds, respectively. Total phosphorus loss for this period was only 0.297 lb/acre from the sheared treatments, but was significantly higher than the chopped or undisturbed treatments. A drop in sediment concentrations and runoff in 1982 reduced phosphorus losses on the sheared watersheds by over 90%. Calcium, potassium and sodium concentrations during 1981, were highest for the chopped treatments, while magnesium concentrations were highest on the sheared treatments. Export of these elements was greatest from the sheared sites, except for calcium, which was lost in greater quantities on the chopped sites. During 1982 there was no significant difference between treatments for Ca, Mg, K and Na concentrations. The rapid revegetation and reduction in exposed mineral soil that occurred on both sheared and chopped treatments during 1982, resulted in a decrease in runoff and sediment and nutrient losses. As the stabilization of sites continues, treatment differences should diminish. Limiting shearing and windrowing activities to the more gentle slopes will reduce first year erosion and prevent increases in sediment and nutrient losses. Roller chopping on the other hand, appears to cause only minor changes to water yield and quality on slopes of up to 25%.

URI:

http://hdl.handle.net/1969.1/6200

Files in this item: 1

tr122.pdf (2.593Mb)

Bacterial Monitoring for the Buck Creek Watershed

Unknown author (Texas Water Resources Institute, NaN)

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Abstract:

The “Bacterial Monitoring for the Buck Creek Watershed” project was developed in response to the creek’s listing on the Texas Water Quality Inventory and 303(d) List due to a bacterial impairment and subsequent total maximum daily load (TMDL) development. Due to limited data, local soil and water conservation districts (SWCD) led the effort to have this TMDL process suspended to allow for further data collection and analysis. The Texas State Soil and Water Conservation Board (TSSWCB) was contacted to seek their assistance in developing and funding a project that would substantially increase the amount of monitoring conducted on the creek. The Texas Water Resources Institute (TWRI) was contracted to develop the project and to coordinate the needed personnel to conduct this study. With the help and cooperation of the Texas AgriLife Research and Extension Center at Vernon, a work plan was developed to collect water samples and conduct water quality monitoring every other week at 13 different sites along the creek. The proposed work plan was then submitted to TSSWCB for funding through the U.S. Environmental Protection Agency’s (EPA) 319 (h) program which focuses on funding activities that address nonpoint source (NPS) pollution. The proposal was approved by EPA and project activities began in October 2003. Sampling began in May 2004 and continued through May 2007 yielding a total of 78 sampling trips. During these trips, a 100 mL water sample was collected and returned to the laboratory for E. coli analysis. Additional water quality parameters including dissolved oxygen (DO), potential hydrogen (pH), salinity, specific conductance, temperature, and water depth were taken. Other information about the current conditions was recorded on field data sheets and included air temperature, when the most recent rain event was, flow and weather conditions. Water samples and their corresponding water quality data were not collected during all sampling trips due to impassable roads, no water present at the site, standing water or flow too low to collect a sample or adverse weather conditions. Data review showed that Buck Creek exhibited elevated bacteria levels at several locations and in some cases, enough to exceed the state’s bacteria standards. State water quality standards dictate that the geometric mean of at least 10 samples collected within a 5-yr time frame must be < 126 colony forming units (cfu) / 100 mL of water and no more than 25 percent of the individual samples collected can exceed 394 cfu / 100 mL. Several individual sites did not meet these criteria and several others were close to exceeding those limits. Results from this study indicate that elevated E. coli levels periodically exist in Buck Creek. Implementing proper management measures in the watershed will aid in decreasing the impacts of E. coli on the creek. Additional information about the sources of bacteria in Buck Creek is needed before sound management measures can be recommended, developed and implemented into a feasible plan of action. A project to collect the needed information and to develop a watershed protection plan (WPP) for Buck Creek has been funded and initiated. Stakeholder support and involvement have grown over the course of the bacterial monitoring project and the continued support and participation of those involved will be vital to successfully improving the creek’s water quality.

URI:

http://handle.tamu.edu/1969.1/86111

Files in this item: 2

TR-318 Bacteria ... e Buck Creek Watershed.pdf (4.692Mb)

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Bacteria Total Maximum Daily Load Task Force Final Report

Ward, George; Srinivasan, Raghavan; Rifai, Hanadi; Mott, Joanna; Hauck, Larry; Di Giovanni, George; Wagner, Kevin; Jones, C. Allan (Texas Water Resources Institute, January 2009)

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Abstract:

In September 2006, the Texas Commission on Environmental Quality (TCEQ) and Texas State Soil and Water Conservation Board (TSSWCB) charged a seven-person Bacteria Total Maximum Daily Load (TMDL) Task Force with: * examining approaches that other states use to develop and implement bacteria TMDLs, * recommending cost-effective and time-efficient methods for developing TMDLs, * recommending effective approaches for developing TMDL Implementation Plans (I-Plans), * evaluating a variety of models and bacteria source tracking (BST) methods available for developing TMDLs and I-Plans, and recommending under what conditions certain methods are more appropriate, and * developing a roadmap for further scientific research needed to reduce uncertainty about how bacteria behave under different water conditions in Texas. The Task Force, assisted by an Expert Advisory Group of approximately 50 stakeholders and agency staff, held two two-hour meetings/teleconferences and developed two drafts of the report. These drafts were shared by e-mail and on a Web site and feedback received from the Expert Advisory Group was also made available on the Web site. The Task Force report describes the characteristics, as well as some of the strengths and weaknesses of several models that have been used and/or are under development to assist bacteria TMDL and I-Plan analysis. These include: * load duration curves (LDC), * spatially explicit statistical models, including Arc Hydro, SPARROW and SELECT, * the mass balance models BLEST and BIT, and * the mechanistic hydrologic/water quality models HSPF, SWAT, SWMM and WASP. The Task Force report also describes and makes recommendations for effective use of BST methods that have been used in Texas and elsewhere for TMDL development. These include ERIC-PCR, Ribotyping, PFGE, KB-ARA, CSU and Bacteroidales PCR. Based on recent experience in Texas and elsewhere, the Task Force recommends using library-independent methods like Bacteriodales PCR for preliminary qualitative analyses and more expensive and time-consuming library-dependent methods if more quantitative data are required for TMDL or I-Plan development. Based on the discussions of bacteria models and source tracking, as well as extensive input from the Expert Advisory Group, the Task Force recommends a three-tier approach to implementing bacteria TMDLs and I-Plans. Tier 1 is a one-year process that includes the formation of a representative stakeholder group, development of a comprehensive geographic information system (GIS) of the watershed, a survey of potential bacterial sources, calculation of load duration curves from existing monitoring data and analysis by agency personnel and stakeholders of data collected for Tier 1. After reviewing information from Tier 1, the group may choose to complete and submit a draft TMDL for agency approval, request an evaluation of the designated use of the water body (an use attainability analysis) or proceed to Tier 2. Tier 2 is a one-to-two-year effort designed to collect targeted monitoring data to fill gaps in previously collected data, conduct qualitative library-independent BST data to determine whether humans and/or a few major classes of animals are sources and develop simple spatially explicit or mass balance models of bacteria in the watershed. After analysis of Tier 1 and Tier 2 data, the group may chose to complete and submit the draft TMDL (or I-Plan if a TMDL was developed after Tier 1), request an evaluation of the designated use (an use attainability analysis), or initiate a “phased TMDL” and proceed with Tier 3 analysis. Tier 3 is a two-to-three-year process designed to continue strong stakeholder involvement, implement more extensive targeted monitoring, conduct quantitative library-dependent BST analysis and develop a detailed hydrologic/water quality model for the watershed. Tier 3 should be implemented only when this level of detailed analysis is needed for I-Plan development or for TMDL development for particularly complex watersheds for which consensus cannot be reached after Tier 2. The Task Force emphasizes that the agencies and stakeholders may choose to deviate from these recommendations if they reach consensus that a more time- and cost-effective approach is feasible. The Task Force concludes its report by summarizing a number of research activities needed to strengthen the scientific tools available for TMDL and I-Plan development. The needed research falls into the following categories: characterization of sources, characterization of kinetic rates and transport mechanisms, enhancements to bacteria fate and transport models and bacteria source tracking, determination of effectiveness of control mechanisms and quantification of uncertainty and risk.

URI:

http://handle.tamu.edu/1969.1/86092

Files in this item: 1

TR-341 Bacteria ... port Draft Four 6.4.07.pdf (971.4Kb)

Bosque River Environmental Infrastructure Improvement Plan: Phase I Final Report

Srinivasan, Raghavan (Texas Water Resources Institute, April 2008)

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Abstract:

The Bosque River and its associated watershed face a myriad of water quality challenges. Previous attempts made to address these concerns have met with limited success due to a relatively narrow, specific problem approach. The goal of this project is to develop a comprehensive plan that considers all aspects of existing issues for collaborators to implement and assist in planning for improved environmental infrastructure. The project set forth will aid in identifying appropriate management practices and structures for rehabilitating and maintaining watershed health from a landscape scale approach. Implementation of an environmental infrastructure program employing a series of best management practices (BMPs) and efforts is desirable for addressing overall watershed health. This report is the first phase of a project that is focused on developing and employing a strategic approach to identifying priority areas in the watershed where field investigations should begin to investigate the need to reduce pollution and in choosing appropriate BMPs for specific areas that are best suited to meet pollution reduction needs both efficiently and economically. There needs to be more in-depth analysis of cost benefits and economic and environmental alternative analysis need to follow in the next phases of this project before any field implementation is undertaken. In-depth analysis using applicable Geographic Information Systems (GIS) data generated specifically for this project identified specific areas of need. Sub-watersheds were evaluated using an impact index that assigns a ranking to each sub-watershed based on three pollution quantifying indices: a concentration impact index, a load per unit area index and a load impact index. The sum of the three index rankings yields the overall ranking for each sub-watershed. A scientific advisory committee developed a list of potential BMPs. The list consists of 22 feasible BMPs that have been assigned a priority index based on potential water quality effects, capital and maintenance costs, and applicability of the practice in the watershed. After establishing the prioritized list, BMPs were evaluated by the Spatial Sciences Lab (SSL) at Texas A&M University using GIS to identify areas within the watershed where implementing these practices would be most effective. Six spatial criteria and six location-specific criteria were used to determine optimum potential locations within the watershed for each BMP to be implemented. This document outlines an effective methodology for determining which locations in the watershed should receive focus when field work begins, and which BMPs would be most effective in specific sub-watersheds. Six steps were identified as an effective process to choose the proper BMP for each sub-watershed in the basin. If these steps are followed, the best BMP(s) for each location should be effectively identified.

URI:

http://handle.tamu.edu/1969.1/86106

Files in this item: 1

TR-312 Bosque R ... Infrastructure Phase I.pdf (7.323Mb)

Bosque River Environmental Infrastructure Improvement Plan: Phase II BMP Modeling Report

Tuppad, Pushpa; Srinivasan, Raghavan (Texas Water Resources Institute, March 2008)

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Abstract:

The Bosque River Watershed is located in the Brazos River Basin in central Texas and is facing a suite of water quality issues resulting in sediment, nutrient and bacteria loading. These loadings are potentially derived from improperly managed cropland and grazing land, land-applied dairy waste, and effluent discharge from eight wastewater treatment plants. The first phase of the project developed an effective methodology for determining priority areas in the watershed where best management practice (BMP) implementation would likely yield the greatest improvements in water quality. The objectives of this project (Phase II) are to apply the Soil and Watershed Assessment Tool (SWAT) model to simulate and evaluate the impacts of implementing several best management practices (a) in the entire watershed, and (b) at incremental levels in high, medium, and low priority areas of the watershed, identified using three different impact indices. Initially, the SWAT model was calibrated for long-term annual and monthly flow at a USGS gaging station located in the lower portion of the watershed for the period from 1980 through 2005 and was validated at the same location for the period 1960 through 1979. The model was also calibrated, at a monthly time step, for water quality parameters including sediment, organic and mineral nitrogen, and phosphorus at two locations, Hico and Valley Mills. Model performance statistics (coefficient of determination and Nash-Sutcliffe modeling efficiency) indicated that model performance was satisfactory and could be used for evaluating the impacts of alternative management scenarios to reduce nonpoint source pollution. BMPs including streambank stabilization, gully plugs, recharge structures, conservation tillage, terraces, contour farming, grazing management, manure incorporation, edge-of-field filter strips, and PL-566 reservoirs were simulated as being implemented in the watershed areas that met the respective practice’s specific criteria for implementation. These BMPs were simulated individually and the resulting farm level (HRU level), subwatershed level, and watershed outlet level impacts were quantified for each BMP. Reductions in sediment load at the watershed outlet, as a result of implementing these BMPs individually, was as much as 37 percent while reductions in total nitrogen (TN) ranged from 1 percent to 24 percent and total phosphorus (TP) varied from a 3 percent increase to a 30 percent decrease. The 3 percent increase is indicative of conservation tillage and is likely caused by the lack of soil inversion and mixing, which yields an accumulation of dissolved (mineral) phosphorus in the soil’s surface layer. At subwatershed levels, reductions brought about by implementing the BMPs were relatively greater as compared to the watershed outlet reductions. Reductions in sediment were as high as 47 percent and reductions in TN and TP were 37 percent and 32 percent, respectively. Subwatersheds were categorized into “high,” “medium,” and “low” priority based on calibrated simulation results. Considering sediment, TN, and TP (as pollutants), three types of total impact indices were estimated. The “Concentration Impact Index” is based on pollutant concentrations (SWAT output values extracted from the ‘reach output file’), considers contributions from the subwatershed as well as the entire upstream watershed, and is effective in determining priority areas for addressing localized pollution problems in low and high flow conditions. The “Load Per Unit Area Impact Index” is based on the total pollutant load coming from a specific area (SWAT output values extracted from the ‘subbasin output file’), considers contributions from an individual subwatershed, and is used to effectively assign a priority to each subwatershed. The “Load Impact Index” is based on pollutant loads from subwatersheds and upstream areas (SWAT output values extracted from the ‘reach output file’) and portrays the cumulative effects of pollutant loading throughout the entire watershed. Priority areas in the watershed varied based on which impact index was used in the evaluation; therefore, the areas where BMP implementations were evaluated differed between simulations. Despite varying BMP implementation sites, all BMPs were modeled incrementally, first on high priority subwatersheds followed by medium and low priority subwatersheds. BMPs considered for implementing in prioritized subwatersheds included streambank stabilization, recharge structures, conservation tillage, terracing, grazing management, and manure incorporation. When comparing the reductions achieved from implementation of BMPs using the three impact indices, load per unit area criteria typically yielded higher pollutant reductions. This outcome is likely a result of the majority of BMPs simulated in this study addressing upland pollutant reductions rather than in-stream reductions. Therefore, these BMPs resulted in larger pollutant reductions because they targeted local upland areas that typically generate higher pollutant loads. Implementing these BMPs in the entire watersheds resulted in sediment, TN, and TP load reductions of 73 percent, 43 percent, and 68 percent, respectively.

URI:

http://handle.tamu.edu/1969.1/86107

Files in this item: 1

TR-313 Bosque Phase II Modeling Report.pdf (2.765Mb)

Break-Even Investment in a Wind Energy Conversion System for an Irrigated Farm on the Texas High Plains

Lacewell, R. D.; Hardin, D. C. (Texas Water Resources Institute, 1981)

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Abstract:

The purpose of this study was to quantify the benefits of using a wind energy system for irrigation. The value of wind energy was estimated on both a static basis (where the annual value of wind power was assumed to be constant over the life of the machine) and on a temporal basis (where the annual value of wind power was estimated recursively). The model for static analysis contained two components which were applied consecutively. The first was a linear programming (LP) model for the High Plains region. Production activities were included which allowed both optimal and non-optimal timing of post-plant irrigations, giving the producer added flexibility in the employment of limiting water resources. The optimal irrigation schedule determined by the LP solution was used as input to the second component. A simulation model matched stochastically generated estimates of wind power availability with irrigation fuel requirements (derived from the profit maximizing irrigation schedule) by three-hour time periods throughout a year. For the temporal analysis, a Fortran subroutine was added to the LP model to operate the model recursively over the life of the wind system and to account for the annual decline of the aquifer. Both fixed and variable costs were included. The basic LP model was applied to develop the benchmark case (i.e., without wind power). The farm operation with wind power was analyzed by applying the LP model with the monthly expectations of wind-generated electricity added. Two wind machines were analyzed, with rate outputs of 40 to 60 kilowatts (KW). Each was applied to the Northern and Southern Texas High Plains over a range of land and water resource situations. Breakeven investment was estimated at discount rates of three, five and ten percent. Cropping patterns on the Southern High Plains were dominated by irrigated cotton and were insensitive to changes in crop or electricity prices. On the Northern High Plains, irrigated corn and grain sorghum were the major crops, with acreage reverting to dryland wheat at the higher electricity prices. The cropping patterns in this area were impacted heavily by labor restrictions. Consideration of wind power had little effect in determining optimal cropping patterns. When wind power was applied to an irrigated farm on a static basis, the set of crop prices applied had little effect on the annual value of a wind system. Value of wind power was increased, but by smaller proportions than associated increases in the price of electricity. Each machine size had a greater value when operated on the larger of the two applicable land units (100 acres for the 40 KW machine and 144 acres for the 60 KW system). The 60 KW system was also tested on the 100 acre unit but returned less per KW than the 40 KW system. Available wind power in the temporal analysis was less than in the static analysis, thus temporal estimates of wind system value should be regarded as conservative. On the Southern High Plains, break-even investment was decreased slightly from the static analysis. However, in some situations on the Northern High Plains, break-even investment increased. This indicates that the value of wind power could increase as the aquifer declines in some situations. Break-even investment increased by up to 80 percent when the price of electricity was increased by $.005 per KWH per year. The most significant effect of wind power was that it allowed the maintenance of irrigation levels which, without wind power, had been made uneconomical. These results indicate that, at least in the future when wind system costs decrease and stabilize, wind-assisted irrigation could be an economically viable alternative for Texas High Plains producers. The results are limited by the need for future research regarding the effect of irrigation timing on crop yield as well as some of the long-term characteristics of wind system operation, such as durability and the requirements and costs for system repairs and maintenance.

URI:

http://hdl.handle.net/1969.1/6259

Files in this item: 1

tr116.pdf (3.904Mb)

Comparative Evaluation of Generalized River/Reservoir System Models

Wurbs, Ralph A. (Texas Water Resources Institute, April 2005)

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Abstract:

This report reviews user-oriented generalized reservoir/river system models. The terms reservoir/river system, reservoir system, reservoir operation, or river basin management "model" or "modeling system" are used synonymously to refer to computer modeling systems that simulate the storage, flow, and diversion of water in a system of reservoirs and river reaches. Generalized means that a computer modeling system is designed for application to a range of concerns dealing with river basin systems of various configurations and locations, rather than being site-specific customized to a particular system. User-oriented implies the modeling system is designed for use by professional practitioners (model-users) other than the original model developers and is thoroughly tested and well documented. User-oriented generalized modeling systems should be convenient to obtain, understand, and use and should work correctly, completely, and efficiently. Modeling applications often involve a system of several simulation models, utility software products, and databases used in combination. A reservoir/river system model is itself a modeling system, which often serves as a component of a larger modeling system that may include watershed hydrology and river hydraulics models, water quality models, databases and various software tools for managing time series, spatial, and other types of data. Reservoir/river system models are based on volume-balance accounting procedures for tracking the movement of water through a system of reservoirs and river reaches. The model computes reservoir storage contents, evaporation, water supply withdrawals, hydroelectric energy generation, and river flows for specified system operating rules and input sequences of stream inflows and net evaporation rates. The hydrologic period-of-analysis and computational time step may vary greatly depending on the application. Storage and flow hydrograph ordinates for a flood event occurring over a few days may be determined at intervals of an hour or less. Water supply capabilities may be modeled with a monthly time step and several decade long period-of-analysis capturing the full range of fluctuating wet and dry periods including extended drought. Stream inflows are usually generated outside of the reservoir/river system model and provided as input to the model. However, reservoir/river system models may also include capabilities for modeling watershed precipitation-runoff processes to generate inflows to the river/reservoir system. Some reservoir/river system models simulate water quality constituents along with water quantities. Some models include features for economic evaluation of system performance based on cost and benefit functions expressed as a function of flow and storage.

URI:

http://hdl.handle.net/1969.1/6092

Files in this item: 1

tr282.pdf (2.704Mb)

Abstract:	Traditionally, water quality monitoring has been focused on chemical attributes such as mineral content, metals, and other contaminants. Biological monitoring is becoming more frequently utilized to assess overall ecological integrity of the water body. Biological monitoring is particularly useful in assessing the effects of nonpoint sources of pollution such as nutrient enrichment and sedimentation. Biological monitoring data collected during this project will provide baseline data that will allow comparisons to be made between sites on the Pecos River as well as comparisons to similar rivers in the state. Monitoring efforts will also provide a baseline for sites along the Pecos River. This data can be used to assess trends and future changes that may occur as conditions in the river change. The development of a sustainable Pecos River Basin water management plan would be a giant first step forward and a great aid to maintaining or increasing populations of endangered species found in the Basin. A healthy, natural watershed and riparian zone is critical to life, especially in semi-arid and desert regions. The U.S. Section International Boundary and Water Commission (USIBWC) Clean Rivers Program (CRP) coordinated a biological assessment with assistance from the Texas Commission on Environmental Quality (TCEQ) in the upper Pecos and with the United State Geological Survey (USGS) in the lower Pecos. Sites were selected along the Pecos River in Texas for assessment of biological condition. At those sites, data on benthic macroinvertebrate organisms, fish, and physical habitat characteristics of the river were collected and catalogued according to protocols previously published by the TCEQ.
Description:	60 pages
URI:	http://hdl.handle.net/1969.1/6068

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