Browsing by Author "Srinivasan, Raghavan"
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Item Bacteria Total Maximum Daily Load Task Force Final Report(Texas Water Resources Institute, 2009-01) Ward, George; Srinivasan, Raghavan; Rifai, Hanadi; Mott, Joanna; Hauck, Larry; Di Giovanni, George; Wagner, Kevin; Jones, C. AllanIn 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.Item Bosque River Environmental Infrastructure Improvement Plan: Phase I Final Report(Texas Water Resources Institute, 2008-04) Srinivasan, RaghavanThe 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.Item Bosque River Environmental Infrastructure Improvement Plan: Phase II BMP Modeling Report(Texas Water Resources Institute, 2008-03) Tuppad, Pushpa; Srinivasan, RaghavanThe 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.Item Brush Management/Water Yield Feasibility Study for Four Watersheds In Texas(Texas Water Resources Institute, 2003) Arnold, Jeff G.; Srinivasan, Raghavan; Dugas, William A.; Rosenthal, Wes; Muttiah, Ranjan S.; Amonett, Carl; Dybala, Tim; Bednarz, Steven T.The Soil and Water Assessment Tool (SWAT) model was used to simulate the effects of brush removal on water yield in four watersheds in Texas for 1960 through 1999. Methods used in this study were similar to methods used in a previous study (TAES, 2000) in which 8 watersheds were analyzed. Landsat 7 satellite imagery was used to classify land use, and the 1:24,000 scale digital elevation model (DEM) was used to delineate watershed boundaries and subbasins. SWAT was calibrated to measured stream gauge flow and reservoir storage. Brush removal was simulated by converting all heavy and moderate categories of brush (except oak) to open range (native grass). Simulated changes in water yield due to brush treatment varied by subbasin, with all subbasins showing increased water yield as a result of removing brush. Average annual water yield increases ranged from about 111,000 gallons per treated acre in the Fort Phantom Hill watershed to about 178,000 gallons per treated acre in the Palo Pinto watershed. Water yield increases per treated acre were similar to a previous study (COE, 2002), but higher than TAES (2000). As in previous studies, there was a strong, positive correlation between water yield increase and precipitation. BACKGROUND Increases in brush area and density may contribute to a decrease in water yield, possibly due to increased evapotranspiration (ET) on watersheds with brush as compared to those with grass (Thurow, 1998; Dugas et al., 1998). Previous modeling studies of watersheds in Texas (Upper Colorado River Authority, 1998; TAES, 2000) indicated that removing brush might result in a significant increase in water yield. During the 2000-2001 legislative session, the Texas Legislature appropriated funds to study the effects of brush removal on water yield in watersheds above Lake Arrowhead, Lake Brownwood, Lake Fort Phantom Hill, and Lake Palo Pinto (Figure 1-1). The hydrologicItem The Development of a Coordinated Database for Water Resources and Flow Model in the Paso Del Norte Watershed(Texas Water Resources Institute, 2006-12) Granados, Alfredo; Srinivasan, Raghavan; Michelsen, Ari; Brown, Christopher; Creel, Bobby; King, Phillip J.; Tillery, Sue; Sheng, Z.This report fulfills the deliverables required by the cooperative agreement between the U.S. Army Corps of Engineers and Texas Agricultural Experiment Station (TAES/03-PL-02: Modification No. 2) on behalf of the Paso del Norte Watershed Council. Tasks accomplished in this phase include (a) review of hydrological models in the region; (b) conceptual model of the Rio Grande flow; and (c) linkage protocol of the coordinated database and hydrological models. In addition, a training workshop on the RiverWare model was offered to regional water stakeholders. Twenty-four trainees attended the workshop at New Mexico State University on December 15-17, 2004. The Project Team also provided review on the FLO-2D model simulation of the Rio Grande flood control scenarios at the U.S. IBWC on August 3, 2005, review of QA/QC procedures of the real-time data collection, and assessment of regional orthophotographic images in 2005. This Project was conducted by researchers at Texas A&M University (TAMU) and New Mexico State University (NMSU) under the direction of Zhuping Sheng of TAMU. It was developed to enhance the coordinated database, which was originally developed by the Paso del Norte Watershed Council with support of El Paso Water Utilities to fulfill needs for better management of regional water resources and to expand the Upper Rio Grande Water Operations Model (URGWOM) to cover the river reaches between Elephant Butte Dam, New Mexico and Fort Quitman, Texas. In Phase I of this Project (TAES/03-PL-02), hydrological data needed for flow model development were compiled and data gaps were identified. The objectives of this phase were to develop a conceptual model of the Rio Grande flow between Elephant Butte Dam and American Dam by using data collected in the first development phase of the PdNWC/Corps Coordinated Water Resources Database and to enhance the data portal capabilities of the PdNWC Coordinated Database Project. The first part of this report (corresponding to Task Five of the contract for the Development of a Coordinated Database and GIS for Water Related Resources in the Rio Grande Watershed, written by Sue Tillery, Phillip King and Zhuping Sheng), summarizes the hydrological models developed for surface water and groundwater flows and management of regional water resources in terms of model configuration, advantages, and limitations of each modeling approach. This part of the report also identifies and verifies the availability of relevant hydrological data needed for development of the RiverWare model, especially hydrology of drain return flows. Based on previous modeling studies, the authors evaluated reasonable simplifications (through the use of look-up tables or similar tools) of interaction of surface and groundwater within the Mesilla Basin and Rincon Valley and developed the RiverWare conceptual model for the Rio Grande flow for the selected reaches and within the limits of available data. The second part of this report was written by C. Brown and B. Creel and summarizes the data portal enhancements to the PdNWC Coordinated Database for its linkage to the URGWOM development. This part of the report describes enhancements to the data portal capabilities of the Project through the development of a low-end user interface that would serve GIS-based graphics of each data set and enhanced metadata of relevant data sets. A literature search of bibliographic resources detailing GIS-based hydrologic modeling in the Paso del Norte region and linkages to these resources are provided via portions of the Project website.Item The Development of a Coordinated Database for Water Resources and Flow Model in the Paso Del Norte Watershed (Phase III) Part I Lower Rio Grande Flood Control Model [LRGFCM] RiverWare Model Development(Texas Water Resources Institute, 2009) Tillery, Sue; Sheng, Zhuping; King, J. Phillip; Creel, Bobby; Brown, Christopher; Michelsen, Ari; Srinivasan, Raghavan; Granados, AlfredoThis report fulfills the deliverables required by the cooperative agreement between the U.S. Army Corps of Engineers and Texas AgriLife Research (TAES/03-PL-02: Modification No. 3) on behalf of the Paso del Norte Watershed Council. Tasks accomplished in this phase include (a) assess the data availability for expansion of the URGWOM model, identify data gaps, generate data needed from historic data using empirical methods, compile and verify the water quality data for reaches between the Elephant Butte Reservoir, New Mexico and Fort Quitman, Texas; (b) develop the RiverWareTM physical model for the Rio Grande flow for the selected reaches between Elephant Butte Reservoir and El Paso, beginning with a conceptual model for interaction of surface water and groundwater in the Rincon and Mesilla valleys, and within the limits of available data; (c) implement data transfer interface between the coordinated database and hydrologic models. This Project was conducted by researchers at Texas A&M University (TAMU) and New Mexico State University (NMSU) under the direction of Zhuping Sheng of TAMU and J. Phillip King of New Mexico State University. It was developed to enhance the coordinated database, which was originally developed by the Paso del Norte Watershed Council with support of El Paso Water Utilities to fulfill needs for better management of regional water resources and to expand the Upper Rio Grande Water Operations Model (URGWOM) to cover the river reaches between Elephant Butte Dam, New Mexico, and Fort Quitman, Texas. In Phases I and II of this Project (TAES/03-PL-02), hydrological data needed for flow model development were compiled and data gaps were identified and conceptual model development. The objectives of this phase were to develop a physical model of the Rio Grande flow between Elephant Butte Dam and American Dam by using data collected in the first development phase of the PdNWC/Corps Coordinated Water Resources Database and to enhance the data portal capabilities of the PdNWC Coordinated Database Project. This report is Part I of a three part completion report for Phase III and describes the development of RiverWare model of Rio Grande flows and a coordinated database for water related resources in the Rio Grande watershed. The RiverWare physical model for Rio Grande flows included selected reaches between Elephant Butte Reservoir and El Paso using historical data from 1985 to 1999. A conceptual model for interaction of surface and groundwater was developed using an ARIMA time-series transfer function analysis. ARIMA transfer functions are used as a means to estimate the interactions of surface and groundwater. Forecasting drain flows from diversion flows is demonstrated as a statistically valid method, and provides results highly correlated with the historic values.Item The Development of a Coordinated Database for Water Resources and Flow Model in the Paso Del Norte Watershed (Phase III) Part II Availability of Flow and Water Quality Data for the Rio Grande Project Area(Texas Water Resources Institute, 2009) Tillery, Sue; Sheng, Zhuping; King, J. Phillip; Creel, Bobby; Brown, Christopher; Michelsen, Ari; Srinivasan, Raghavan; Granados, AlfredoThis report fulfills the deliverables required by the cooperative agreement between the U.S. Army Corps of Engineers and Texas AgriLife Research (TAES/03-PL-02: Modification No. 3) on behalf of the Paso del Norte Watershed Council. Tasks accomplished in this phase include (a) assess the data availability for expansion of the URGWOM model, identify data gaps, generate data needed from historic data using empirical methods, compile and verify the water quality data for reaches between the Elephant Butte reservoir, New Mexico and Fort Quitman, Texas; (b) develop the RiverWare physical model for the Rio Grande flow for the selected reaches between Elephant Butte Reservoir and El Paso, beginning with a conceptual model for interaction of surface water and groundwater in the Rincon and Mesilla valleys, and within the limits of available data; (c) implement data transfer interface between the coordinated database and hydrologic models. This Project was conducted by researchers at Texas A&M University (TAMU) and New Mexico State University (NMSU) under the direction of Zhuping Sheng of TAMU and J. Phillip King of New Mexico State University. It was developed to enhance the coordinated database, which was originally developed by the Paso del Norte Watershed Council with support of El Paso Water Utilities to fulfill needs for better management of regional water resources and to expand the Upper Rio Grande Water Operations Model (URGWOM) to cover the river reaches between Elephant Butte Dam, New Mexico and Fort Quitman, Texas. In Phases I and II of this Project (TAES/03-PL-02), hydrological data needed for flow model development were compiled and data gaps were identified and conceptual model was developed. The objectives of this phase were to develop a physical model of the Rio Grande flow between Elephant Butte Dam and American Dam by using data collected in the first development phase of the PdNWC/Corps Coordinated Water Resources Database and to enhance the data portal capabilities of the PdNWC Coordinated Database Project. This report is Part II of a three part completion report that combines data compilation of the Phase I report prepared by Sue Tillery and J. Phillip King and part of the completion report for Phase III prepared by Z. Sheng, J.P. King and B. Creel. It identifies and evaluates the availability of historical flow and water quality data that has been collected at different sites along the Rio Grande between Elephant Butte Dam, New Mexico and Fort Quitman, Texas. This includes monitoring sites from associated canals, drains, and dams along the Rio Grande. Flow data for the years from 1908 through 2002 and water quality data for the years 1938 to 2005 collected periodically by different agencies include historic chemical analytical results and real-time monitoring values. This report includes a description of the agencies that collected water quality data, a summary of the sites found along the Rio Grande, and finally a data matrix and parameter summary for each site. Data downloaded were collected from the U.S. International Boundary and Water Commission (USIBWC), El Paso, Texas; US Geological Survey (USGS), U.S. Bureau of Reclamation, Elephant Butte Irrigation District (EBID), El Paso County Water Improvement District No. 1, and Parsons Engineering Science, Inc. compiled for the New Mexico-Texas Water Commission by contract through El Paso Water Utilities.Item The Development of a Coordinated Database for Water Resources and Flow Model in the Paso Del Norte Watershed (Phase III) Part III GIS Coverage for the Valle de Juárez Irrigation District 009 (ID-009) (Distrito de Riego 009) Chihuahua, México(Texas Water Resources Institute, 2009) Sheng, Zhuping; King, J. Phillip; Creel, Bobby; Brown, Christopher; Michelsen, Ari; Srinivasan, RaghavanThis report fulfills the deliverables required by the cooperative agreement between the U.S. Army Corps of Engineers and Texas Agricultural Experiment Station (TAES/03-PL- 02: Modification No. 3) on behalf of the Paso del Norte Watershed Council. Tasks accomplished in this phase include (a) assessment of data availability for expansion of the URGWOM model, identification of data gaps, generation of data needed from historic data using empirical methods, compilation and verification of the water quality data for reaches between the Elephant Butte Reservoir, New Mexico and Fort Quitman, Texas; (b) development of the RiverWare physical model for the Rio Grande flow for the selected reaches between Elephant Butte Reservoir and El Paso, beginning with a conceptual model for interaction of surface water and groundwater in the Rincon and Mesilla valleys, and within the limits of available data; and (c) implementation of data transfer interface between the coordinated database and hydrologic models. This Project was conducted by researchers at Texas A&M University (TAMU) and New Mexico State University (NMSU) under the direction of Zhuping Sheng of TAMU and J. Phillip King of New Mexico State University. It was developed to enhance the coordinated database, which was originally developed by the Paso del Norte Watershed Council with support of El Paso Water Utilities to fulfill needs for better management of regional water resources and to expand the Upper Rio Grande Water Operations Model (URGWOM) to cover the river reaches between Elephant Butte Dam, New Mexico and Fort Quitman, Texas. In Phases I and II of this Project (TAES/03-PL-02), hydrological data needed for flow model development were compiled and data gaps were identified and a conceptual model developed. The objectives of this phase were to develop a physical model of the Rio Grande flow between Elephant Butte Dam and American Dam by using data collected in the first development phase of the PdNWC/Corps Coordinated Water Resources Database and to enhance the data portal capabilities of the PdNWC Coordinated Database Project. This report is Part III of a three part completion report for Phase III and provides information on water sources, uses, and GIS of the canals and ditches of the Valle de Juárez Irrigation District 009 (ID 009) in the Juárez Lower Valley, Chihuahua, México. The author explains that the water needs of this region have changed in recent years from being primarily for agricultural purposes to domestic and industrial uses currently. Also, the United States wanted to assess and identify new data sources on a GIS format for the Mexican side. Therefore, this project produced several maps with the location of channels and ditches along the Valle de Juárez Irrigation District. This information also will support water planning of the Valle de Juárez Irrigation District 009. The maps were produced from existing digital data regarding water resources and by adding thematic layers such as soil salinity and soil texture from analog maps. ASTER satellite imagery and official panchromatic aerial photography were used to produce the maps.Item Ecosystem and Wildlife Implications of Brush: Management System Designed to Improve Water Runoff and Percolation(Texas Water Resources Institute, 2002-11-01) Jarboe, Hank; Griffith, Rebecca; Dybala, Tim; Bednarz, Steve; Amonett, Carl; Wilkins, Neal; Zinn, Michele; Winemiller, Kirk O.; Srinivasan, Raghavan; Rosenthal, Wes; Olenick, Keith; Muttiah, Ranjan; Magness, Dawn; Hejl, Sallie; Dugas, William; Conner, Richard; Arrington, D. AlbreyWith the settlement of Texas and establishment of ranchers to produce cattle, there was an effort to maximize beef production. This caused serious overgrazing. In addition, there was a reduced incidence of fires across the landscape to clear out brush. These factors led to deterioration of the grazing lands and provided an opportunity for invasive intrusion by brush and other species onto the land and riparian zones. There has been a large-scale conversion from grasslands and savannahs to wildlands over the last 150 years (Scholes and Archer, 1997). The overall impacts are significantly impaired uplands and reduced percolation and surface flow of water from rainfall which caused changes and loss in basic aquatic and terrestrial habitat. The State of Texas adopted a program to study and implement brush management systems across the state to improve the water availability in streams, rivers, reservoirs and aquifers, as well as to improve the rangelands. The feasibility studies have shown great promise for improving ranchland and improving the water situation. However, there is less known about the aquatic and wildlife species response implications of brush management. Certainly, there are opportunities for improving the viability of an ecosystem through brush management strategies and continuing management practices. The purpose of this study was to evaluate the changes in hydrology and biological diversity associated with brush management in two watersheds where significant data was already available. This study focused on assessing the aquatic and terrestrial species implications related to specified brush management strategies over time. This involved an integrated analysis including modeling of the landscape, assessing biological diversity and developing economic implications for the two watersheds (Twin Buttes and Edwards regions). Thus, this study is comprised of three parts: modeling of brush management strategies temporally, assessing biological diversity (aquatic and terrestrial) and estimating economic implications. This represents a complex analysis involving variable units and multiple disciplines. Previous feasibility studies of brush removal have been targeted at maximizing water runoff. This analysis is an extension that is designed to examine the implications of brush management under a more restrictive set of brush removal criteria that were chosen based upon wildlife considerations. To achieve the integration of hydrologic modeling, range ecology, and economic implications, there were three team meetings bringing together all components to review status and set priorities for the remainder of the work. In addition, scientists in the three basic groups of specialization interacted daily along with representatives of the Corps of Engineers to assure that each decision was reflected in other parts of the analyses. The major addition of this analysis to brush management feasibility studies being conducted as part of the Texas brush management plan is the consideration of wildlife and aquatic biota and assessing changes in biological diversity likely to result from alternative brush management scenarios.Item Institutional Adjustments for Coping with Prolonged and Severe Drought in the Rio Grande Basin(Texas Water Resources Institute, 2001-02) Srinivasan, Raghavan; Ellis, John; Booker, James; DuMars, Charles R.; Frasier, Marshall; McGuckin, J. Thomas; King, J. Philip; Lacewell, Ronald D.; Young, Robert; Ward, Frank A.The Rio Grande originates in the southern Colorado Rocky Mountains, flows through New Mexico, and forms the border between the U.S. and Mexico on its way to the Gulf of Mexico. Serving over one-million acres of irrigated land and the municipal and industrial needs of cities like Albuquerque and El Paso, the Rio Grande represents a significant resource in the arid southwest. In 1938, Congress approved the Rio Grande Compact which divided the annual water flow among the three states of Colorado, New Mexico, and Texas. The U.S.-Mexico Treaty of 1906 divides the river flows between the U.S. and Mexico. The Compact acknowledges the Treaty in Articles IV and VI by stating that the Compact shall not diminish the allocation of water to Mexico and shall not degrade its quality. Since that time, significant growth in the Rio Grande Basin’s demand for water due to increasing populations, growing economies, and emerging policies toward fish and wildlife habitat emphasizing endangered species, has stressed the region’s already scarce water supply. Although the inevitable severe drought would cause significant economic damage to the regional economy, present institutional arrangements have not had to confront such an event since the 1950s. The objective of this research is to test the hypothesis that new institutions for interstate coordination of surface water withdrawal and reservoir operations could reduce economic losses resulting from water shortfalls in periods of severe and sustained drought. A three-state research team of economists, hydrologists and a lawyer was formed to perform the analysis to test this hypothesis. A fully-integrated hydrologic-economic model was developed which extends the basin optimization procedures developed by Vaux and Howitt for California and by Booker and Young for the Colorado River Basin. The geographic scope included the Rio Grande Basin, from Colorado through New Mexico to Fort Quitman, Texas, downstream of El Paso. The objective was to identify hydrological and economic impacts of possible changes in institutional structure for coping with drought. This study was an effort to examine options facing river basin managers when confronted with the extenuating circumstance of a major drought. It did not attempt a precise description of the current system as it is managed. The research team realizes that many considered institutional changes for managing water considered in this report would be difficult to do, costly, and in some cases fought bitterly. Nevertheless, like other analyses of proposed changes in water policy, there are several reasons for conducting these policy experiments. Estimating impacts of a proposed water policy change can be a cheap substitute for carrying it out, especially if carrying it out has potentially high but unknown political or economic costs or benefits. If a proposed policy change produces a low economic benefit and high cost for many water users, information on the size and distribution of those benefits and costs is important. This information is a valuable resource for formulating or executing this action should it be considered is a real possibility. If, however, there is a high benefit and low cost to most water users, this is also important information to get out, for it may influence the shape of future policies pursued. The general approach used in this study reflected the random supplies and uncertain demands for water. They also reflect river and reservoir management rules resulting from economic growth and competing demands for water to meet future needs such as endangered species habitats. Water supplies, which included all major tributaries, interbasin transfers, and hydrologically connected groundwater, were represented in a yearly time-step over a forty-four year planning horizon. Agricultural water uses, the major source of water demands, were split into major crops for four major demand areas. Municipal and Industrial (M&I) and recreational demands were also identified. Separate economic values were identified for each water use at each major location. Information on the economic value of each water use at each location provides important facts to decision makers who wish to know impacts of complex proposals whose implementation affects several uses at many locations. A mathematical model was developed that kept track of economic benefits subject to hydrologic and institutional constraints, and was solved with GAMS optimization software (Appendix CD ROM). Each institutional innovation considered was tested against the baseline Law of the River, the current set of rules for storing, allocating, and using water in the basin. Each proposal was tested for its impact on reducing total economic damages under a future, long-run drought scenario defined by inflows produced by the drought of the 1950s. Results are presented as economic and hydrologic impacts of measures for coping with drought by state, economic sector, and institutional alternative. One baseline and three alternative institutional innovations were selected for evaluation. The baseline Law of the River focused primarily on the Rio Grande Compact and related rules for allocating the total quantity of water entering the Rio Grande Basin and available for use. Total economic benefits were calculated for: (1) long run normal inflows, (2) a sequence of drought inflows, defined by historical inflows for the period 1942-1985. This period was chosen to represent the severe drought of the 1950s bound by the years leading up to and following that drought. The period was extended to 1942 and 1985 because spills occurred in these two years, wiping out accrued debits and credits under the Compact. For that period, average inflows summed over six headwater stream gages used for this study were 1.40 million acre-feet per year, about 11 percent below the long-run average of 1.57 million. Total drought damages were computed as the reduction in future economic benefits if future inflows to the basin averaged 1.40 million acre-feet per year compared to economic benefits if inflows averaged 1.57 million. Future economic activity is based on best available estimates for growth in M&I uses based on projected growth of the Albuquerque and El Paso areas. Long-run annual average future drought damages, defined as the direct economic value of damages caused by the reduced streamflows to water users, were estimated at $5.8 million for the San Luis Valley (Colorado), $3.37 million for New Mexico, and $8.0 million for west Texas, or about $101 per acre-foot of water supply reduction. Indirect economic impacts, resulting from interactions among drought-damaged water-users and the rest of the economy, were not measured. The first institutional adjustment analyzed was increased carryover storage at Elephant Butte Reservoir. This carryover storage was based on reducing Rio Grande project deliveries downstream of Elephant Butte by 25,000 acre-feet per year in normal years, to be stored for use in drought years. The long- run average annual economic value of drought damages mitigated by this institutional change was zero for Colorado, minus $200,000 for New Mexico, and minus $433,000 for west Texas. This means that the current Law of the River produces less drought damage than the proposed institution of storing the added water at Elephant Butte. The second institutional adjustment analyzed was a proposal to invest in technical measures to increase irrigation efficiency for the Middle Rio Grande Conservancy District, in which net stream depletions required for application to crops would be reduced by 18 percent. This institutional change produced virtually zero drought damage mitigation to each of the three states. Reduced water diverted from the Rio Grande brought about by greater irrigation efficiency would also considerably reduce irrigation return flows to the river. The result would be virtually zero water saved and essentially zero economic benefit. Zero drought damage mitigation benefits accrued to Colorado, $7,000 per year to New Mexico, and $15,000 to West Texas. This means that the cost of technologies needed to implement these increased irrigation efficiencies would have to be virtually zero to justify such investments economically. The final institutional adjustment analyzed was to build 100,000 acre feet of new reservoir storage in northern New Mexico above Cochiti Lake. This action produced zero long-run average annual benefit to Colorado, $134,000 to New Mexico water users, and $685,000 to West Texas water users. The bulk of these benefits would result from reduced reservoir evaporation and reduced Rio Grande Compact over-deliveries by New Mexico to Texas. Although the model developed for this study was comprehensive and detailed, it has several limitations in its current state. Overall, it does not precisely represent the behavior of the Rio Grande Basin system. One special area where further improvement is needed is to develop a better understanding and modeling of connections among economics, surface water movement, groundwater hydrology, and behavior of water users. If improved models are to be used to support development, execution, and evaluation of proposed decisions, considerable resources need to be put into model development and use. The kind of integrated, basin-wide modeling described in this report is a new area of research. The integrations required between modeling the behavior of water users and underlying natural processes are quite complex, poorly understood, and will require much work and patience to bring to full fruition. Nevertheless, this study succeeded in organizing a highly integrated interdisciplinary study dealing with water management in an important western river basin. Most western river basins are under stress, from natural factors like drought, institutional factors such as endangered species requirements, and external factors like economic growth. The use of interdisciplinary teams to build and apply models such as described in this report, helps prepare society for dealing with unexpected circumstances, such as drought, to cope with future stresses on river basins.Item SWAT 2003: 2nd International SWAT Conference Proceedings(Texas Water Resources Institute, 2003-07) Jensen, Ric; Jacobs, Jennifer; Srinivasan, RaghavanThis book of proceedings presents papers that were given at the 2nd International SWAT Conference, SWAT 2003, that convened in 2003 in Bari, Italy. The focus of this conference was to allow an international community of researchers and scholars to discuss the latest advances in the use of the SWAT (Soil Water Assessment Tool) model to assess water quality trends. SWAT is a comprehensive computer simulation tool that can be used to simulate the effects of point and nonpoint source pollution from watersheds, in the streams, and rivers. SWAT is integrated with several readily available databases and Geographic Information Systems (GIS). Because of the versatility of SWAT, the model has been utilized to study a wide range of phenomena throughout the world. At the same time, the research community is actively engaged in developing new improvements to SWAT for site-specific needs and linking SWAT results to other simulation models. This conference provided an opportunity for the international research community to gather and share information about the latest innovations developed for SWAT and to discuss challenges that still need to be resolved. This proceedings includes papers covering a variety of themes, including new developments associated with SWAT, applications of the SWAT model, the use of related modeling tools, how SWAT can be calibrated or compared to other models, the use of other simulation models and tools, and integrating SWAT with other models. In addition to papers presented at SWAT 2003, posters shown at the conference are also included in this proceeding.