Browsing by Subject "SWAT"
Now showing 1 - 14 of 14
Results Per Page
Sort Options
Item A water quality assessment of the import of turfgrass sod grown with composted dairy manure into a suburban watershed(Texas A&M University, 2005-02-17) Richards, Chad EdwardConcentrated animal feeding operations (CAFOs) have caused water quality concerns in many rural watersheds, sometimes forcing the State of Texas to conduct Total Maximum Daily Load (TMDL) assessments of stream nutrients such as nitrogen (N) and phosphorus (P). One suggested Best Management Practice (BMP) is the export of phosphorus (P) through turfgrass sod produced with composted dairy manure from an impaired rural watershed to an urban watershed. The manure-grown sod releases P slowly and would not require additional P fertilizer for up to 20 years in the receiving watershed. This would eliminate P application to the sod and improve the water quality of urban streams. The Soil and Water Assessment Tool (SWAT) was used to model a typical suburban watershed that would receive the transplanted sod. The objective of the modeling was to determine the water quality changes due to the import of sod transplanted from turf fields and grown with composted dairy manure. The SWAT model was calibrated to simulate historical flow and sediment and nutrient loading to Mary's Creek. The total P stream loading to Mary's Creek was lower when manure-grown sod was imported instead of commercial sod grown with inorganic fertilizers. Yet, flow, sediment yield, and total N yield increased equally for both cases at the watershed outlet. The SWAT simulations indicate that a turfgrass BMP can be used effectively to import manure P into an urban watershed and reduce in-stream P levels when compared to sod grown with inorganic fertilizers.Item Development of an ArcGIS interface and design of a geodatabase for the soil and water assessment tool(Texas A&M University, 2004-09-30) Valenzuela Zapata, Milver AlfredoThis project presents the development and design of a comprehensive interface coupled with a geodatabase (ArcGISwat 2003), for the Soil and Water Assessment Tool (SWAT). SWAT is a hydrologically distributed, lumped parameter model that runs on a continuous time step. The quantity and extensive detail of the spatial and hydrologic data, involved in the input and output, both make SWAT highly complex. A new interface, that will manage the input/output (I/O) process, is being developed using the Geodatabase object model and concepts from hydrological data models such as ArcHydro. It also incorporates uncertainty analysis on the process of modeling. This interface aims to further direct communication and integration with other hydrologic models, consequently increasing efficiency and diminishing modeling time. A case study is presented in order to demonstrate a common watershed-modeling task, which utilizes SWAT and ArcGIS-SWAT2003.Item Development of indices for agricultural drought monitoring using a spatially distributed hydrologic model(Texas A&M University, 2005-11-01) Narasimhan, BalajiFarming communities in the United States and around the world lose billions of dollars every year due to drought. Drought Indices such as the Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI) are widely used by the government agencies to assess and respond to drought. These drought indices are currently monitored at a large spatial resolution (several thousand km2). Further, these drought indices are primarily based on precipitation deficits and are thus good indicators for monitoring large scale meteorological drought. However, agricultural drought depends on soil moisture and evapotranspiration deficits. Hence, two drought indices, the Evapotranspiration Deficit Index (ETDI) and Soil Moisture Deficit Index (SMDI), were developed in this study based on evapotranspiration and soil moisture deficits, respectively. A Geographical Information System (GIS) based approach was used to simulate the hydrology using soil and land use properties at a much finer spatial resolution (16km2) than the existing drought indices. The Soil and Water Assessment Tool (SWAT) was used to simulate the long-term hydrology of six watersheds located in various climatic zones of Texas. The simulated soil water was well-correlated with the Normalized Difference Vegetation Index NDVI (r ~ 0.6) for agriculture and pasture land use types, indicating that the model performed well in simulating the soil water. Using historical weather data from 1901-2002, long-term weekly normal soil moisture and evapotranspiration were estimated. This long-term weekly normal soil moisture and evapotranspiration data was used to calculate ETDI and SMDI at a spatial resolution of 4km ?? 4km. Analysis of the data showed that ETDI and SMDI compared well with wheat and sorghum yields (r > 0.75) suggesting that they are good indicators of agricultural drought. Rainfall is a highly variable input both spatially and temporally. Hence, the use of NEXRAD rainfall data was studied for simulating soil moisture and drought. Analysis of the data showed that raingages often miss small rainfall events that introduce considerable spatial variability among soil moisture simulated using raingage and NEXRAD rainfall data, especially during drought conditions. The study showed that the use of NEXRAD data could improve drought monitoring at a much better spatial resolution.Item Evaluation of Scale Issues in SWAT(2010-07-14) Mylevaganam, SivarajahIn Soil and Water Assessment Tool (SWAT), oftentimes, Critical Source Area (CSA), the minimum upstream drainage area that is required to initiate a stream, is used to subdivide a watershed. In the current literature, CSA has been used as a trial and error process to define the subwatershed levels. On the other hand, the ongoing collaboration of the United States Environmental Protection Agency Office of Water and the United States Geological Survey has promoted a national level predefined catchments and flowlines called National Hydrography Dataset (NHD) Plus to ease watershed modeling in the United States. The introduction of NHDPlus can eliminate the uncertain nature in defining the number of subwatersheds required to model the hydrologic system. This study demonstrates an integrated modeling environment with SWAT and NHDPlus spatial datasets. A spatial tool that was developed in a Geographical Information System (GIS) environment to by-pass the default watershed delineation in ArcSWAT, the GIS interface to SWAT, with the introduction of NHDPlus catchments and flowlines, was used in this study. This study investigates the effect of the spatial size (catchment area) of the NHDPlus and the input data resolution (cell/pixel size) within NHDPlus catchments on SWAT streamflow and sediment prediction. In addition, an entropy based watershed subdivision scheme is presented by using the landuse and soil spatial datasets with the conventional CSA approach to investigate if one of the CSAs can be considered to produce the best SWAT prediction on streamflow. Two watersheds (Kings Creek, Texas and Sugar Creek, Indiana) were used in this study. The study shows that there exists a subwatershed map that does not belong to one of the subwatershed maps produced through conventional CSA approach, to produce a better result on uncalibrated monthly SWAT streamflow prediction. Beyond the critical threshold, the CSA threshold which gives the best uncalibrated monthly streamflow prediction among a given set of CSAs, the SWAT performance can be improved further by subdividing some of the subwatersheds at this critical threshold. The study also shows that the input data resolution (within each NHDPlus catchments) does not have an influence on SWAT streamflow prediction for the selected watersheds. However, there is a change on streamflow prediction as the area of the NHDPlus catchment changes. Beyond a certain catchment size (8-9% of the watershed area), as the input data resolution becomes finer, the total sediment increases whereas the sediment prediction in high flow regime decreases. As the NHDPlus catchment size changes, the stream power has an influence on total sediment prediction. However, as the input data resolution changes, but keeping the NHDPlus catchment size constant, the Modified Universal Soil Loss Equation topographic factor has an influence on total sediment prediction.Item Evaluation of shrub encroachment and brush control on water availability in the Upper Guadalupe River watershed(Texas A&M University, 2004-09-30) Afinowicz, Jason DavidWooded plant encroachment has dramatically changed the composition of rangelands in the arid and semiarid rangelands of the southwestern United States and may have significantly affected hydrologic and biogeochemical process in these environments. In particular, suspicions that encroaching species waste an undue amount of water through evapotranspiration (ET) has prompted much discussion concerning the possibility of using brush control to enhance water supplies in Texas. This study focuses on two broad goals for evaluating the effects of wooded growth in rangelands. The first of these is the assessment of wooded cover with the use of remotely sensed imagery. A methodology for delineating differing land cover classes, including different levels of brush cover, is described, applied, and validated for the Upper Guadalupe River watershed, Texas. This portion of the research resulted in an 81.81% success rate for correctly matching land cover varieties and showed that 88.8% of the watershed was covered with various amounts of woody plant growth. The second portion of this study incorporated the previously developed land cover product along with a number of other highly detailed data sources to model the North Fork of the Upper Guadalupe River watershed using the Soil and Water Assessment Tool (SWAT). The role of topography, brush cover, and soil slope, which are hypothesized to contribute to successful implementation of brush removal for water yield, were tested in a scientifically conscious and practical experiment to determine their influence upon water availability at a watershed scale. The effects of brush removal were found to be comparable to the quantities documented in field experiments, but less than the levels presented in previous modeling studies. Brush density was found to be the most important factor in determining locations for successful brush removal in regards to reducing ET. Slope was also found to have significant effect in increasing lateral flow while shallow soil had lesser effects on hydrology than other criteria. Large quantities of deep recharge simulated by the model raise questions concerning measurement of ET in the Edwards Plateau region and the extent of deep water recharge to the Trinity Aquifer.Item Feedstock Logistics of a Mobile Pyrolysis System and Assessment of Soil Loss Due to Biomass Removal for Bioenergy Production(2012-10-19) Bumguardner, MarisaThe purpose of this study was to assess feedstock logistics for a mobile pyrolysis system and to quantify the amount of soil loss caused by harvesting agricultural feedstocks for bioenergy production. The analysis of feedstock logistics was conducted using ArcGIS with the Network Analyst extension and model builder. A square grid methodology was used to determine biomass availability of corn stover and bioenergy sorghum in Texas. The SWAT model was used to quantify soil erosion losses in surface runoff caused by sorghum residue removal for bioenergy production in the Oso Creek Watershed in Nueces County. The model simulated the removal of 25, 50, 75, and 100 percent residue removal. The WEPS model was used to quantify wind erosion soil loss caused by corn stover removal in Dallam County. Nine simulations were run estimating soil loss for corn stover removal rates of 0 percent to 50 percent. The results of the SWAT and WEPS analyses were compared to the NRCS tolerable soil loss limit of 5 tons/acre/year for both study areas. The GIS analysis determined the optimum route distances between mobile unit sites were 2.07 to 58.02 km for corn and 1.95 to 60.36 km for sorghum. The optimum routes from the mobile pyrolysis sites and the closest refineries were 49.50 to 187.18 km for corn and 7.00 to 220.11 km for sorghum. These results were used as input to a separate bioenergy economic model. The SWAT analysis found that maximum soil loss (1.24 tons/acre) occurred during the final year of the simulation where 100 percent of the sorghum residue was removed. The WEPS analysis determined that at 30 percent removal the amount of soil loss starts to increase exponentially with increasing residue removal and exceeds the tolerable soil loss limit. Limited harvesting of biomass for bioenergy production will be required to protect crop and soil productivity ensuring a sustainable biomass source.Item Impact Assessment of Climate Change on Glaciers and Runoff Using SWAT(2014-08-08) Omani, NinaA modified incorporated snow algorithm in Soil and Water Assessment Tool (SWAT) was applied to consider spatial variation of associated snow parameters by elevation band for flow simulation of five mountainous river basins with different climatic conditions including the Narayani (Nepal), Vakhsh (Central Asia), Rhone (Switzerland), Mendoza (Central Andes, Argentina), and Central Dry Andes (Chile) with total area of 85,000 km^(2). The results by modified snow algorithm implied slight to noticeable improvement in simulation of flow cycles and volume depend on the percentage of glacier area and climatic type of a subbasin. The ability of model in simulation of glacier mass balance and Equilibrium Line Altitude (ELA) then was evaluated for three reference glaciers and their neighboring glacier ranges across the Europe and central Asia. The modified model successfully simulated the annual glacier loss, mass balance profile and annual ELAs with light calibration efforts and limited data. The results revealed that even very good result in monthly runoff simulation alone does not imply the consistency between simulated and measured mass balances. Calibrating the model versus flow data in combination with data of glaciers considerably reduced the model parameterization uncertainty and enhanced mass balance simulation accuracy. To assess the range of future climate change impacts on the glacier runoff, we used maximum, minimum air temperature and precipitation projections under two RCPs (Representative Concentration Pathway) climate change scenarios and six Coupled Model Intercomparison Project-5 (CMIP5) models. Simulations of mean annual and monthly runoff, high (Q5) and low (Q95) monthly runoff and flow duration curves (FDCs) under baseline (1979?2008) and climate change scenarios are presented for all river basins. The variation of ELA related to a moderate climate change scenario then was predicted for a test study area. Therefore, the objectives of this study are: 1. Evaluating SWAT?s snow hydrologic component in glaciered basins, 2. Improvement of SWAT snow/ice melt processing, 3. Extending the applied method to macro-scale river basins, 4. Assessing the effect of future climate change on the streamflow volume and seasonal variability with focusing on glaciered areas, 5. Investigating that the global mountainous glaciers will be vanished by 2100.Item Modeling Impacts of Land-Use/Land-Cover Change and Variable Precipitation on Hydrology and Water Quality of a Coastal Watershed in Texas(2013-05-31) Castillo, Cesar RicardoLand use/land cover (LULC) change and variations in precipitation can alter the quantity and quality of freshwater flows. The Mission-Aransas (M-A) estuary depends on inputs of freshwater and material from streams in order to maintain its ecological integrity. Freshwater inflow estimates for the M-A estuary have been established, but no analyses using scenarios of LULC change and precipitation variability have been conducted that inform how freshwater inflows could be impacted. A land change analysis for the M-A region was conducted by classifying two Landsat images for the years 1990 and 2010. A large degree of LULC change occurred within the M-A region during this time; with 27.1% of the land area experiencing LULC change. Furthermore, developed land increased by 44.9%. A SWAT hydrological model was developed to model the quantity and quality of freshwater inflows. SWAT was calibrated at a monthly scale using data from a stream gage. Model evaluations indicated that the model had a good performance rating with a Nash-Sutcliffe model efficiency coefficient (NS) of 0.66 and coefficient of determination (R2) of 0.66 for the calibration period; and an NS of 0.76 and R2 of 0.78 for the validation period. Three LULC change scenarios and three precipitation scenarios were developed to be used in a scenario analysis with the calibrated SWAT model. Each LULC change scenario represents a different amount of developed land (3.4, 3.7, and 4.7% of watershed area). Precipitation data was analyzed to select weather data for each precipitation scenario that each had different amounts of annual precipitation (763, 907, and 996 mm). A scenario analysis was conducted that analyzed how stream/channel flows and loads of sediment, total nitrogen, and total phosphorus were impacted under scenario conditions. A general increase in all output variables was exhibited as the amount of precipitation and developed land increased; with impacts from precipitation variability outweighing impacts from varying amounts of developed land. Furthermore, sediment loads were the variable most impacted by differing amounts of developed land. This study provides information on how LULC and precipitation can influence watershed hydrology that can be used in watershed management for the M-A region.Item Modeling Low Impact Development at the Small-Watershed Scale: Implications for the Decision Making Process(2014-12-03) Seo, MijinNegative effects of urban stormwater runoff on water environment have been a growing concern in the United States. Drastic change in land uses to urban communities with pavements from natural land uses can destroy the already established eco-hydrologic system prior to the land conversion. Low Impact Development practices (LIDs) have been used as an alternative stormwater management approach in urban areas. The effects of LIDs on hydrology and water quality have been widely accepted to be positive through research that generally indicates decrease in surface runoff volume and pollutant loads. However, LIDs can have varying effectiveness under different conditions. In this research, the effectiveness of LIDs was assessed under three urban development plans (compact high-density (UHD), conventional medium-density (UMD), and conservational medium-density (UMC)) and under various configurations of LIDs factors (types, locations, and percent allocations) for surface runoff, nitrate, and total phosphorus in order to identify their performance on improving stormwater runoff and water quality under such conditions. Rain gardens, rainwater harvesting systems, and permeable pavements, commonly used in urban areas, were selected. The Soil and Water Assessment Tool (SWAT) was modified to implement the LIDs simulations at a watershed scale. A manual optimization was attempted to identify the LIDs configurations that meet targeted reduction amounts in a cost-effective manner. Then the effectiveness of LIDs was evaluated for the three urban plans and for the optimized LIDs configurations. The research indicates that the effectiveness of LIDs varies under various conditions examined. Under urban development plans, the efficiency of LIDs was measured in the order of the following land uses for all variables: UMD > UMC > UHD. Among post-LIDs scenarios, the UHD scenario resulted in low amounts in surface runoff and nitrate while the UMD scenario predicted low TP yields. Under LIDs factors through the optimization, the various configurations of type, location, and percent allocation changed the effectiveness of LIDs and/or caused the same effectiveness of LIDs for each variable. This research is useful in that it can ultimately suggest proper strategies in urban watersheds to effectively control stormwater and help regulators establish effective LID policies based on the results.Item Modeling the Effects of Low Impact Development Practices on Streams at the Watershed Scale(2014-04-28) Shannak, Sa'D AUrban growth contributes to increasing storm water runoff which in turn causes an increase in the frequency and severity of flooding. Moreover, increased storm water runoff contributes to changing the character and volume of energy inputs to the stream. Traditionally, storm water management controls such as detention pond had been extensively studied and evaluated with respect to reducing and controlling peak flows. Nonpoint source pollutants due to urbanization and expanding of agricultural fields have become a big burden on municipalities and states. Low Impact Development practices were developed to negate the negative impacts of urbanization on water resources by reducing the runoff volume and peak flows as well as improving outflow water quality. Though these practices have the capability of reducing runoff volumes and enhancing outflow water quality, they can be costly. Therefore, understanding the impact of installing LID practices on a watershed scale is becoming increasingly important. In this study, field experiment and model study were applied to evaluate the effectiveness of LID practices on a watershed scale in the Blunn Creek Watershed located in Austin, Texas. The three LID practices which were evaluated in this study are permeable pavements, a bioretention area, and a detention pond. The main objective of this study was to investigate the influences of these practices at a watershed scale on: potential reduction on channel bank erosion, potential reduction on flood, and potential impact on aquatic life. This study was one of very few studies that take place in the Blackland clay soil in Texas. A combination of different levels of LID practices such as permeable pavement and bioretention area resulted with achieving the main goal of this study of reducing stream bank erosion, bankfull exceedance, and maintaining acceptable flows for the integrity of aquatic life habitat. All LID practices have shown significant difference with respect to a control treatment at 95% confidence ratio. Performance of the modeled LID practices was validated by showing acceptable agreement in the percentage of reductions in total runoff between field experiments and model data.Item Modeling the Hydrologic Impact of Arundo Donax on the Headwaters of the Nueces River Using the Swat Model(2014-08-06) Jain, ShaileeThe invasive species Arundo donax (hereafter Arundo), has invaded the riparian zones of the Rio Grande River and the rivers of the Texas Hill Country over the last two decades. Arundo, also known as the giant cane, is a robust herbaceous plant that can grow in many different climatic conditions. Arundo was first observed along the Nueces River in 1994 by the Nueces River Authority (NRA). It then spread rapidly downstream due to its high growth rate and/or stream flow and completely displaced the native vegetation, primarily P. virgatum (hereafter switchgrass), in the riparian zone wherever it got established. An eradication program was started in 2010 by the NRA to remove Arundo from the Nueces River. The objective of this research project was to (1) develop an algorithm to simulate the propagation of Arundo, (2) study changes in streamflow patterns during pre- and post- Arundo invasion periods, (3) calibrate and validate the Soil Water Assessment Tool (SWAT) for the Nueces River Headwater (HUC 12110101) watershed in central Texas, and (4) assess the effects of the invasion of Arundo on the watershed hydrology by comparing it to the native grass species switchgrass (Panicum virgatum) that used to be the dominant species in the watershed. Arundo parameters appropriate for the Nueces River were added to create a new crop category in the SWAT database. Calibration and validation of SWAT were based on measured streamflow data available at the USGS gage (USGS 08910000) on the Nueces River for the period 1960 to 1994. Switchgrass, the native vegetation, was chosen as the plant to compare Arundo with so that the difference in hydrology could be understood. The results revealed that accumulated evapotranspiration was not statistically different between Arundo and switchgrass for the period of 16 years (1995-2010). There was also no difference in the water yields of Arundo and switchgrass. In conclusion it appears that Arundo in the Nueces River has not caused any changes in water uptake compared to the native grass, switchgrass, that previously dominated the headwaters.Item Optimizing Feedstock Logistics and Assessment of Hydrologic Impacts for Sustainable Bio-Energy Production(2012-12-11) Ha, Mi-Ae 1979-Rising world petroleum prices and global warming are contributing to interest in renewable energy sources, including energy produced from agricultural crops and waste sources of biomass. A network of small mobile pyrolysis units may be the most cost effective system to convert biomass from agricultural feedstocks to bio-crude oil. Mobile pyrolysis units could be moved to the feedstock production fields thereby greatly simplifying feedstock logistics. In the North Central (NC) region of the U.S., possible feedstocks are corn stover, energy sorghum, and switchgrass. A grid-based Geographic Information System (GIS) program was developed to identify optimum locations for mobile pyrolysis units based on feedstock availability in the NC region. Model builder was used to automate the GIS analysis. Network analysis was used to find the best route to move the mobile pyrolysis units to new locations and to identify the closest refinery to transport the bio-crude oil. To produce bioenergy from feedstocks, the removal of biomass from agricultural fields will impact the hydrology and sediment transport in rural watersheds. Therefore, the hydrologic effects of removing corn stover from corn production fields in Illinois (IL) were evaluated using the Soil Water Assessment Tool (SWAT). The SWAT model was calibrated and validated for streamflow and sediment yields in the Spoon River basin in IL using observed data from the USGS. The modeling results indicated that as residue removal rates increased, evapotranspiration (ET) and sediment yields increased, while streamflows decreased. Biochar is a carbon-based byproduct of pyrolysis. To ensure that the mobile pyrolysis system is economically and environmental sustainable, the biochar must be land applied to the feedstock production fields as a soil amendment. An assessment of hydrologic changes due to the land application of biochar was made using the SWAT model in the Spoon River basin and changes in soil properties due to incorporation of biochar into the soil obtained from laboratory experiments by Cook et al. (2012). Model simulations indicated that a biochar application rate of 128 Mg/ha decreased water yield, and sediment yield in surface runoff and increased soil moisture and ET.Item Water quality improvements in the Upper North Bosque River watershed due to phosphorous export through turfgrass sod(Texas A&M University, 2005-02-17) Stewart, George RussellThe Upper North Bosque River (UNBR) watershed is under a Total Maximum Daily Load (TMDL) mandate to reduce Phosphorus (P) due to excess nutrients in the watershed. To address these problems, Texas A&M University researchers have developed a turfgrass sod Best Management Practice (BMP) to remove excess nutrients from impaired watersheds. Turfgrass harvest of manure fertilized sod removes a thin layer of topsoil with most of the manure applied P. Plot and field scale research has demonstrated the effectiveness of turfgrass to remove manure phosphorus (P). In order to assess the impact of the turfgrass BMP on a watershed scale, the Soil and Water Assessment Tool (SWAT) was used to predict water quality in the UNBR watershed. The SWAT model was modified to incorporate turfgrass harvest routines to predict manure and soil P export through turfgrass sod and soil during harvest. SWAT simulations of the BMP predicted stream load reductions of 20 to 36% for P loads in the UNBR depending on the implementation scenario, an average reduction of 31% for total N and 16.7% for sediment for all the scenarios, at the watershed outlet. The SWAT model also predicted up to 176 kg/ha P removed per sod harvest when fertilized with 100 kg manure P/ha, and 258 kg/ha of P removed per sod harvest when the manure P application rate was 200 kg/ha. In addition, depending on the implementation scenario, the turfgrass BMP could export between 262 and 784 metric tons of P out of the UNBR watershed every year. Manure fertilized turfgrass has the advantage of slow releasing nutrients from the composted dairy manure, so it would not require any additional P for life. This means reduced urban non-point source pollution and lower maintenance cost compared to regular sod. These modeling simulations complement the wealth of research that shows the effectiveness of the turfgrass BMP.Item When Sugar Turns to Sh%&: Immediate Action Decision Making and Resilience in High Reliability Teams(2012-02-14) Wesner, Bradley ScottOrganizational scholars have long been interested in organizations which exemplify high reliability. While such organizational studies have provided valuable clues to the ways in which such organizations form and function, this paper argues that a more nuanced study of high reliability processes within team contexts is warranted. This study focuses on organizational teams which are faced with the challenges of maintaining high levels of reliability. Of particular interest is how teams manage adverse events which disrupt the team's process and how they make adaptations immediately to restore their functionality. In my dissertation, I: (1) explore the existing literature surrounding high reliability organization and resilience, (2) present a qualitative analysis of Special Weapons and Tactics (SWAT) teams to explore and identify factors surrounding adaptation within the critical moment, and (3) discuss the implications of these factors in the theory and research surrounding high-reliability teams. The findings of this study find strong connection with the work of Weick and serve to advance and clarify previous characteristics associated with high reliability organizing; however, by using the small group as the unit of analysis for the study additions to concepts traditionally associated with high reliability organizing can be noted: (1) controlling variability during team function, (2) accepting the value of the unexpected, (3) continuous forward motion, and (4) the role of tacit and explicit knowledge.