A total maximum daily load (TMDL) assessment in the Upper North Bosque River (UNBR) has mandated reductions of soluble reactive phosphorus (SRP). The large concentrations of dairies in the UNBR watershed have been identified as a source of the SRP. Agricultural best management practices (BMPs) can be used to reduce in-stream loads of manure nutrients from confined dairy feeding operations (CAFOs). A new BMP utilizes turfgrass sod to export composted dairy manure nutrients out of the impaired watershed in a sustainable manner. Previous plot-scale experiments have showed that 46 to 77% of applied phosphorus (P) and 36 to 47% of applied nitrogen (N) were removed in a single sod harvest. Two, 1.4 ha turfgrass fields were instrumented to measure runoff flow and sediment and nutrient transport. One turfgrass field was topdressed with composted dairy manure and fertilizer N and the other with fertilizer N only. A total of 3.5% of the applied manure P and 3.1% of applied manure N were lost in the surface runoff over a 1.5 year period. The runoff data from the experimental fields were used to calibrate and validate Soil and Water Assessment Tool (SWAT) model simulations of flow, sediment, organic, and mineral nutrients. The Nash-Sutcliffe model fit statistic was greater than 0.6 for flow, sediment, and nutrients during the calibration period and greater than 0.3 during the validation period. Research results indicated that turfgrass sod can be used to export composted dairy manure out of impaired watersheds to improve water and soil quality.

The research focus is on the various modeling aspects of flow and sediment transport in water bodies and watersheds. The interaction of flow with a mobile bed involves a complex process in which various turbulent scales characterized by coherent structures cause a chaotic sediment motion. In many rivers and natural waterways secondary flows that are dominating flow struc-tures bring about more complications. In estuaries and open waterbodies thermal stratification and internal mixing control the flow structure besides the flow interaction with the mobile bed. To adequately model these processes 3D coupled flow and transport models are needed. The research is based on use and adaptation of open source codes for 3D hydrodynamic and sediment transport model known as Estuarine Coastal Ocean Model (ECOMSED) and the Soil and Water Assessment Tool (SWAT) model. A bed load transport model was developed and coupled to ECOMSED. The flow and sediment transport characteristics in a curved channel and a river reach were successfully captured by the model. Improvements in ECOMSED were made to study the effect of wind and basin bathymetry on mixing and flow exchange between two estuaries. Using spectral analysis the hydrological component of SWAT model was investigated for its applicability under limited data conditions in three Ethiopian catchments. / QC 20100827

Microbial contamination of drinking water poses an important health risk which causes severe illnesses and epidemics. In order to improve surface and drinking water quality, the understanding of fecal pathogen contamination processes including their prevention and control needs to be enhanced. The watershed model soil water assessment tool (SWAT) is commonly used to simulate the complex hydrological, meteorological, erosion, land management and pollution processes within river basins. In recent years, it has been increasingly applied to simulate microbial contamination transport at the watershed scale. SWAT is used in this study to simulate Escherichia coli (E.coli) and fecal coliform densities for the agriculturally dominated Payne River Basin in Ontario, Canada. Unprecedented extensive monitoring data that consist of 30 years of daily hydrological data and 5 years of bi-weekly nutrient data have been used to calibrate and validate the presented model here. The calibration and validation of the streamflow and nutrients indicate that the model represent these processes well. The model performs well for periods of lower E. coli and fecal coliform loadings. On the other hand, frequency and magnitude of higher microbial loads are not always accurately represented by the model.

Microbial contamination of drinking water poses an important health risk which causes severe illnesses and epidemics. In order to improve surface and drinking water quality, the understanding of fecal pathogen contamination processes including their prevention and control needs to be enhanced. The watershed model soil water assessment tool (SWAT) is commonly used to simulate the complex hydrological, meteorological, erosion, land management and pollution processes within river basins. In recent years, it has been increasingly applied to simulate microbial contamination transport at the watershed scale. SWAT is used in this study to simulate Escherichia coli (E.coli) and fecal coliform densities for the agriculturally dominated Payne River Basin in Ontario, Canada. Unprecedented extensive monitoring data that consist of 30 years of daily hydrological data and 5 years of bi-weekly nutrient data have been used to calibrate and validate the presented model here. The calibration and validation of the streamflow and nutrients indicate that the model represent these processes well. The model performs well for periods of lower E. coli and fecal coliform loadings. On the other hand, frequency and magnitude of higher microbial loads are not always accurately represented by the model.

Concentrated 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.

The 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.

Farming 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.

A total maximum daily load (TMDL) assessment in the Upper North Bosque River (UNBR) has mandated reductions of soluble reactive phosphorus (SRP). The large concentrations of dairies in the UNBR watershed have been identified as a source of the SRP. Agricultural best management practices (BMPs) can be used to reduce in-stream loads of manure nutrients from confined dairy feeding operations (CAFOs). A new BMP utilizes turfgrass sod to export composted dairy manure nutrients out of the impaired watershed in a sustainable manner. Previous plot-scale experiments have showed that 46 to 77% of applied phosphorus (P) and 36 to 47% of applied nitrogen (N) were removed in a single sod harvest. Two, 1.4 ha turfgrass fields were instrumented to measure runoff flow and sediment and nutrient transport. One turfgrass field was topdressed with composted dairy manure and fertilizer N and the other with fertilizer N only. A total of 3.5% of the applied manure P and 3.1% of applied manure N were lost in the surface runoff over a 1.5 year period. The runoff data from the experimental fields were used to calibrate and validate Soil and Water Assessment Tool (SWAT) model simulations of flow, sediment, organic, and mineral nutrients. The Nash-Sutcliffe model fit statistic was greater than 0.6 for flow, sediment, and nutrients during the calibration period and greater than 0.3 during the validation period. Research results indicated that turfgrass sod can be used to export composted dairy manure out of impaired watersheds to improve water and soil quality.

Ο σκοπός της εργασίας είναι η ανάλυση της χωρικής κατανομής των κατολισθητικών φαινομένων στην υδρολογική λεκάνη του Βουραϊκού ποταμού. Απώτερος σκοπός είναι η δημιουργία ενός χάρτη ευστάθειας πρανών (χάρτης επικινδυνότητας) ο οποίος θα μπορεί να παρέχει σημαντικές πληροφορίες για περιοχές επιδεκτικές σε κατολίσθηση. / -

Land 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.