Composted biological wastes contain vital plant nutrients that assist in plant growth as well as contain organic matter that promotes good soil conditions; both aid in rangeland restoration. Most importantly, it has the potential to restore water availability through increased infiltration and reduced runoff. In this thesis, local sources of composted dairy manure are utilized for application onto the degraded Fort Hood Western Training Grounds in central Texas in hopes to restore the rangeland for continued military training. Small scale rainfall simulations are applied two and eight months post-application of seven different agronomic rates of composted waste treatment (0, 5, 10, 15, 20, 25, and 30 y^3/acre) in order to determine changes in infiltration rates. July 2004 rainfall simulations, two months post application, indicate that composted wastes have not had sufficient time to incorporate into the soil matrix. Percent organic matter of the parent soil is the only significant variable of impact on maximum infiltration capacity. Composted waste treatments are concluded to have no effect on infiltration rates for any of the application rates in the summer rainfall simulations and are observed to exhibit very high variability in the amount of infiltration by a plot. January 2005 rainfall simulations, eight months post waste application, are observed to continue the trend of high variability across all treatment application rates. This variability is attributed to masking any potential effects from the treatment applications. Overall, this high natural variability disables the detection of potential effects of waste application treatments leading to the conclusion that composted waste applications do not affect infiltration on the Fort Hood Western Training Grounds. Runoff nutrient analysis observed nitrate-N to be well below Texas drinking water standards for all plots and phosphate to be above non-standardized values known to cause problematic algal growth. Natural rainfall events at intensities needed to generate runoff observed in this study are rare; therefore, nutrient pollution concern for local water bodies is low.

Two experimental rainfall simulation plots in the Edwards Aquifer region of Texas were established to measure the effects of brush clearing on surface and subsurface water movement pathways. Multi-stage rainfall simulations were carried out at a site with Juniperus ashei (ashe juniper) cover both before and after brush removal, with three replications of a particular rainfall event for each vegetation condition. Similar simulations were carried out on a plot with a longstanding grass cover. Both plots included trenches at their downhill ends for observation of shallow lateral subsurface flow. Canopy interception was found to represent a major water loss, with interception of 32.7 mm for an average 166 mm, 5.25 hr rainfall event. Brush clearing had little impact on surface runoff, with no overland flow occurring at the juniper plot for either vegetation condition, while 31.9 percent of applied rainfall moved as overland flow at the grass plot. This difference was attributed to differences in the structure and permeability of the epikarst. Brush removal caused significant (90 percent confidence level) reduction in shallow lateral subsurface flow into the trench after brush removal, with 56.7 percent of water reaching the surface entering the trench for the pre-cut condition and only 43.4 percent for the post-cut condition. However, subsurface water movement through other pathways increased from 31.0 to 54.1 percent after brush removal. This additional water, due to removal of canopy interception, could either move off-site through conduit and fracture flow or remain on site as storage in conduits, unconsolidated caliche/marl layers, or in soil pockets. Two tracer tests with fluorescent dyes were also conducted using simulated rainfall to assess discrete flow paths discharging into the trench at the downhill end of the juniper plot. Analysis of samples from sixteen outlet locations revealed that not all areas of the plot were connected hydraulically to the trench. Additionally, subsurface flow paths were found to have a high degree of interconnection, linking conduit flow outlets with multiple inlet locations on the plot surface. Conduits showed strong connection with an area surrounding juniper vegetation, with rapid water flow (up to 2.4 m/h) from this area.

From an agronomic perspective, the spreading of manure (sometimes containing antibiotics) onto agricultural fields is beneficial to the soil as a renewable source of fertilizer by increasing organic matter and providing nutrient inputs for crops. However, the use of antibiotics can be excessive, resulting in manures containing residual antibiotics contaminating soils and waterways. Thus, there is a need to improve existing or develop new management practices to minimize the losses of antibiotics from manure entering waterways and groundwater. Biochar is a carbon-rich material produced from the oxygen-free pyrolysis of biomass. Generally, biochars have high surface area and sorb organic compounds and trace metals; thus, it is reasonable to hypothesize that biochars sorb antibiotics. The main goal of this research was to investigate if incorporated biochar to soil facilitates the transport of antibiotics under simulated rainstorm events. The specific objectives were to investigate the losses of surface-applied antibiotics to soils with different (1) application rates of biochar and rainfall intensities, and (2) if the losses were antibiotic type-dependent. <br>

Les sols sableux peuvent constituer une réserve potentielle de sols cultivables mais leur mise en valeur entraîne toujours des dégradations de la structure et une baisse du potentiel agricole. Une dégradation très fréquente est l’affaissement des couches labourées sous l’action de la pluie, ou slumping. Notre objectif était d’identifier les mécanismes et les facteurs déterminants du slumping afin de proposer des techniques de prévention. L’étude a été conduite sous pluies naturelles (au champ) et simulées (au laboratoire). Au champ, la cinétique d’évolution des caractéristiques hydriques et physiques du sol a été suivie après un labour à 20 ou à 40 cm de profondeur, dans un sol sableux tropical Thaïlande. Au laboratoire, un sol cultivé modèle a été élaboré dans un cylindre (h et Ø = 20 cm) à partir i) du sol prélevé dans le champ expérimental, ii) de la fraction sable (> 50 μm) extraite de ce même sol. Les sols modèles ont subi des pluies d’intensité variable (de 20 à 120 mm/h) après mise en place sur une table à succion (20 à 90 hPa). Le slumping se produit lorsque deux conditions sont réunies: (1) l’eau doit atteindre un potentiel proche de 0 hPa ce qui réduit la cohésion et aboutit à un équilibre fragile du sol comme décrit par la physique des milieux granulaires; (2) ce potentiel doit être maintenu assez longtemps pour qu’une instabilité se produise et entraine une brusque et importante diminution de la cohésion, donc l’effondrement du matériau. Si la fraction fine (<50 μm) est retirée du sol, aucun effondrement n’est observé, démontrant l’importance de cette fraction limonoargileuse, pourtant minoritaire (<10-15 % en masse), dans l’instabilisation et le slumping. La prévention du slumping et la gestion des sols sableux sont discutées en guise de conclusion. / The sandy soil can serve as a potential reserve for cultivation. However, they are often considered as marginal because prone to have low productivity and problems of structure degradation. One of the degradations is compaction caused by rainfall or irrigation, which is called slumping. Our objective is to identify the processes and factors that affect slumping. The study had been done under natural conditions (field) and simulated conditions (laboratory) respectively. In the field, a tropical sandy soil in Thailand was selected. After 20 cm and 40 cm depth tillage, the dynamic of hydraulic and physical characteristics were measured. In laboratory, a cultivated soil model was build in a cylinder (height and diameter was 20 cm). We used two materials: 1) the original soil from the experiment field site, and 2) the sand fraction (> 50 μm) extracted from this soil. These model soils were submitted to rainfalls with different intensity (20 to 120 mm h-1), combined with different suction (20 to 90 hPa) on a suction table which can support the cylinder. The slumping for soil happens when two conditions were met: 1) the water potential reached a threshold value near 0 hPa. In this value, the soil cohesion decreased and a fragile equilibrium conditions were reached according to granular material theory; 2) the potential value was kept long enough and the cohesion continue decrease until they can no more support the equilibrium, so slumping happens. Surprisingly, in our treatment, when the fine particles (<50 μm) were taken out from the soil, no slumping was observed. This demonstrates the particles of clay and silt are very important to soil stability, even their content were very low as less than 10 percent. The possible ways to prevent slumping and management of sandy soils are also discussed.

Magister Scientiae - MSc / The primary origin of this project is due to a high demand for freshwater supply in the Berg Water Management Area (WMA). Most of the Berg WMA`s freshwater supply does not live up to the high ecological standards. This is mainly due to high sediments loading in the Berg River which is one of the water supplies to the Berg WMA. The project was conducted on a small-scale catchment at Langgewens experimental farms in Swartland district. The focus of this study was to address some of the hydrological processes active in the research catchment: infiltration, run-off and sediment mobilization on different soil types under wheat and canola vegetation cover. This was done to investigate the origin of sediments in the Berg River. Considering the results, one might conclude that the decayed root systems from the canola and wheat vegetation covers, organic matter content, soil cracks, slope orientation, and soil composition, all played a major role in influencing the ability of the soil to absorb the simulated rainfall. Because the infiltration was calculated using the difference between the incoming simulated rainfall and the measured run-off, there was an inverse relationship between run-off and infiltration. When run-off was low, the infiltration was high and vice versa. iv Factors that governed sediment mobilisation within the ring area are micro topography within the ring area, the slope gradient and vegetation covers. Considering the results, vegetation cover played a pivotal role and it must be maintained at all times. It is advisable that the land users leave crop residual cover behind after the annual harvest and not expose the land surface in bare form for too long as this will generate more run-off and increase sediment mobilisation. The analyses showed that wheat crop protects the soil from rain drop impact than on canola crop.

Measurements of runoff quantity and quality from three cattle stocking treatments applied to pastureland in southwestern Virginia indicate the need for further research to determine treatment effects. Three cattle stocking treatments (1) Continuous, 2) Rotational, and 3) Mob) were applied to three pastures at the Virginia Tech Prices Fork Research Farm. Rainfall simulations were performed over replicated plots in each treatment to induce runoff for collection of runoff quantity and quality data during the 2012 grazing season. Additionally, rainfall simulations were performed prior to applying the grazing treatments to establish initial conditions. Monitored runoff quantity and quality response variables included runoff depth, mean nutrient concentrations, and nutrient mass loss. Response variables were compared among the three pastures for initial conditions and among treatments for post-treatment conditions. Additionally, the trends in response variables within the 2012 season were compared among treatments. Plot and rainfall conditions that were expected to influence responses were also collected and analyzed in relation to response variables. Analyses of the response variables suggested that the variability within treatments likely muted any treatment effect on the response variables. Therefore, we concluded that further research is needed to determine treatment effects on runoff quantity and quality. / Master of Science

Made available in DSpace on 2014-06-11T19:31:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-05-06Bitstream added on 2014-06-13T20:41:10Z : No. of bitstreams: 1 sousa_gb_dr_jabo.pdf: 1449920 bytes, checksum: 805de1eda80021c1476ccc1c0e5cf804 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O escoamento superficial da água provoca o transporte dos nutrientes do solo, quando este encontra-se com a superfície desprotegida de cobertura. O presente trabalho teve como objetivo avaliar as possíveis relações entre posições do relevo, erosão em entressulcos e seus reflexos nas perdas de solo, matéria orgânica e nutrientes em área cultivada com a cultura de cana-de-açúcar submetida à colheita mecanizada. Parcelas experimentais foram submetidas à ação de uma chuva simulada com intensidade de 60 mm h-1, durante 65 minutos. Foram feitas análises do sedimento erodido para determinar perdas de solo, matéria orgânica e nutrientes. Houve maiores perdas de solo, matéria orgânica e nutrientes no sedimento das parcelas com 0% e 25% de cobertura por palha de cana-de-açúcar. Em média, as perdas no sedimento erodido foram significativamente reduzidas nas parcelas com 75% e 100% de cobertura por resíduos de palha de cana-de-açúcar. Na perda de água, observou-se que houve diferenças estatísticas das médias dos níveis de cobertura 0% e 25% em relação aos demais (50%, 75% e 100%) em todas as posições da vertente. No topo, a diferença do maior valor (168.600 L ha-1) para o menor valor (120.300 L ha-1) foi de 48.300 L ha-1. Os resultados permitem concluir que acima de 50% da cobertura com palhada, na área estudada, reduz a perda de solo e matéria orgânica, e a concentração de nutrientes no sedimento erodido / The water superficial drainage provokes the transport of soil nutrients especially in unprotected surfaces. The present work had as objective to evaluates the possible relationship between positions in a relief and soil losses induced by erosion in an area cultivated with the sugarcane under mechanized harvest. The studied plots were submitted to simulate rain events with intensity of 60 mm h-1, for 65 minutes. The analyses of eroded sediments in terms of volume, soil losses, organic matter and nutrients were conducted. There were larger sediment losses at plots with 0% and 25% of sugarcane crop residues cover. On average, the losses in the eroded sediment were significantly reduced in the portions with 75% and 100% surface residues covering. In terms of water loss it was also observed significant differences between 0% and 25% to the others (50%, 75% and 100%) in all positions in the slope. In the top the difference of the largest value 168,600 L ha-1 for the smallest value 120,300 L ha-1 it was of 48,300 L ha-1. The results points that 50% of crop residues covering would reduce soil losses, including organic matter and nutrients

Spatial variability of soil properties complicates the understanding of water and solute transport at the field scale. This study evaluated the impact of land use, soil surface roughness, and rainfall characteristics on water transport and Br- leaching under field conditions by means of a new experimental design employing scale-dependent treatment distribution. On a transect with two land use systems, i.e., cropland and grassland, rainfall intensity and the time delay between Br- application and subsequent rainfall were arranged in a periodically repetitive pattern at two different scales. Both scales were distinct from the scale of surface roughness as described by elevation variance. Nests of tensiometers and suction probes were installed at 1-m intervals along the transect to monitor matric potentials and Br- concentrations at different depths, respectively. After rainfall simulation, soil samples were collected at every 0.5 m horizontal distance in 10 cm vertical increments down to 1 m depth for Br- analysis. Soil Br- concentration was more evenly distributed with soil depth and leached deeper in grassland than cropland, owing to vertically continuous macropores that supported preferential flow. Frequency-domain analysis and autoregressive state-space approach revealed that the dominant factors controlling Br- leaching varied with depth. In shallow layers, land use was the main driving force for Br- distribution. Beyond that, the spatial pattern of Br- was mostly affected by rainfall characteristics. Below 40 cm, the horizontal distribution of Br- was dominated by soil texture and to a smaller extent by rainfall intensity. Bromide concentrations obtained from soil solution samples that were collected through suction probes showed similar results with respect to the influence of rainfall intensity. The spatial variation scale of temporal matric potential change varied with both time and depth, corresponding to different boundary condition scales. Matric potential change in some cases, reflected the impact of soil properties other than the boundary conditions investigated, such as hydraulic conductivity, contributing to the scale-variant behavior of Br- leaching. These findings suggest the applicability of scale-dependent treatment distribution in designing field experiments and also hold important implications for agricultural management and hydrological modelling.

The research described in the thesis details the investigation of build-up and wash-off process kinetics of Polycyclic Aromatic Hydrocarbons (PAHs) and heavy metals in urban areas. It also discusses the design and development of a rainfall simulator as an important research tool to ensure homogeneity and reduce the large number of variables that are usually inherent to urban water quality research. The rainfall simulator was used to collect runoff samples from three study areas, each with different land uses. The study areas consisted of sites with typical residential, industrial and commercial characteristics in the region. Build-up and wash-off samples were collected at each of the three sites. The collected samples were analysed for a number of chemical and physico-chemical parameters. In addition to this, eight heavy metal elements and 16 priority listed PAHs were analysed in five different particle size fractions of the build-up and wash-off samples. The data generated from the testing of the samples were evaluated using multivariate analysis, which reduced the complexity involved in determining the relative importance of a single parameter in urban water quality. Consequently, variables and processes influencing loadings and concentrations of PAHs and heavy metals in urban stormwater runoff from paved surfaces at any given time were identified and quantified using Principal Component Analysis (PCA). Furthermore, the process kinetics found were validated using a multivariate modelling approach and Partial Least Square (PLS) regression, which confirmed the transferability of chemical processes in urban water quality. Fine particles were dominant in both the build-up and wash-off samples from the three sites. This was mirrored in the heavy metal and PAH concentrations at the three sites, which were significantly higher in particles between 0.45-75μm than in any other fraction. Thus, the larger surface area and electrostatic charge of fine particles were favourable in sorbing PAHs and heavy metals. However, factors such as soil composition, total organic carbon (TOC), the presence of Fe and Mn-oxides and pH of the stormwater were all found to be important in partitioning of the metals and PAHs into different fractions. Additionally, PAHs were consistently found in concentrations above their aqueous solubility, which was attributed to colloidal organic particles being able to increase the dissolved fraction of PAHs. Hence, chemical and physico-chemical parameters played a significant role in the distribution of PAHs and heavy metals in urban stormwater. More importantly, the research showed the wide range of factors that distribute metals and PAHs in an urban environment. Furthermore, it indicated the need for monitoring these parameters in urban areas to ensure that urban stormwater management measures are effective in improving water quality. The build-up and wash-off process kinetics identified using PCA at the respective land uses were predicted using PLS and it was found that the transferability of the governing processes were high even though the PAHs and metal concentrations and loads were highly influenced by the source strength at each site. The increased transferability of fundamental concepts in urban water quality could have significant implications in urban stormwater management. This is primarily attributed to common urban water quality mitigation strategies relying on studies based on physical concepts and processes derived from water quantity studies, which are difficult to transfer between catchments. Hence, a more holistic approach incorporating chemical processes compared to the current piecemeal solutions could significantly improve the protection of key environmental values in a region. Furthermore, urban water quantity mitigation measures are generally designed to reduce the impacts of high-flow events. This research suggests that fairly frequent occurring rainfall events, such as 1-year design rainfall events, could carry significant heavy metal and PAH concentrations in both particulate and dissolved fractions. Hence, structural measures, designed to decrease quantity and quality impact on receiving waters during 10 or 20-year Average Recurrence Interval (ARI) events could be inefficient in removing the majority of PAHs and heavy metals being washed off during more frequent events. The understanding of physical and chemical processes in urban stormwater management could potentially lead to significant improvements in pollutant removal techniques which in turn could lead to significant socio-economic advantages. This project can serve as a baseline study for urban water quality investigations in terms of adopting new methodology and data analysis.

Accurate and reliable estimations are the most important factors for the development of efficient stormwater pollutant mitigation strategies. Modelling is the primary tool used for such estimations. The general architecture of typical modelling approaches is to replicate pollutant processes along with hydrologic processes on catchment surfaces. However, due to the lack of understanding of these pollutant processes and the underlying physical parameters, the estimations are subjected to gross errors. Furthermore, the essential requirement of model calibration leads to significant data and resource requirements. This underlines the necessity for simplified and robust stormwater pollutant estimation procedures. The research described in this thesis primarily details the extensive knowledge developed on pollutant build-up and wash-off processes. Knowledge on both build-up and wash-off were generated by in-depth field investigations conducted on residential road and roof surfaces. Additionally, the research describes the use of a rainfall simulator as a tool in urban water quality research. The rainfall simulator was used to collect runoff samples from small-plot surfaces. The use of a rainfall simulator reduced the number of variables which are common to pollutant wash-off. Pollutant build-up on road and roof surfaces was found to be rapid during the initial time period and the rate reduced when the antecedent dry days increase becoming asymptote to a constant value. However, build-up on roofs was gradual when compared to road surfaces where the build-up on the first two days was 66% of the total build-up. Though the variations were different, it was possible to develop a common replication equation in the form of a power function for build-up for the two surface types with a as a multiplication coefficient and b as a power coefficient. However, the values for the two build-up equation coefficients, a, and b were different in each case. It was understood that the power coefficient b varies only with the surface type. The multiplication coefficient varies with a range of parameters including land-use and traffic volume. Additionally, the build-up observed on road surfaces was highly dynamic. It was found that pollutant re-distribution occurs with finer particles being removed from the surface thus allowing coarser particles to build up. This process results in changes to the particle size composition of build-up. However, little evidence was noted of re-distribution of pollutants on roof surfaces. Furthermore, the particulate pollutants in both road and roof surfaces were high in adsorption capacity. More than 50% of the road and more than 60% of the roof surface particulates were finer than 100 μm which increases the capacity to adsorb other pollutants such as heavy metals and hydrocarbons. In addition, the samples contained a significant amount of DOC which would enhance the solubility of other pollutants. The wash-off investigations on road and roof surfaces showed a high concentration of solid pollutants during the initial part of events. This confirmed the occurrence of the 'first flush' phenomenon. The observed wash-off patterns for road and roof surfaces were able to be mathematically replicated using an exponential equation. The exponential equation proposed is a modified version of an equation proposed in past research. The modification was primarily in terms of an additional parameter referred to as the 'capacity factor' (CF). CF defines the rainfall's ability to mobilise solid pollutants from a given surface. It was noted that CF varies with rainfall intensity, particle size distribution and surface characteristics. Additional to the mathematical replication of wash-off, analysis further focused on understanding the physical processes governing wash-off. For this, both particle size distribution and physicochemical parameters of wash-off pollutants were analysed. It was noted that there is little variation in the particle size distribution of particulates in wash-off with rainfall intensity and duration. This suggested that particle size is not an influential parameter in wash-off. It is hypothesised that the particulate density and adhesion to road surfaces are the primary criteria that govern wash-off. Additionally, significantly high pollutant contribution from roof surfaces was noted. This justifies the significance of roof surfaces as an urban pollutant source particularly in the case of first flush. This dissertation further describes a procedure to translate the knowledge created on pollutant build-up and wash-off processes using small-plots to urban catchment scale. This leads to a simple and robust urban water quality estimation tool. Due to its basic architecture, the estimation tool is referred to as a 'translation procedure'. It is designed to operate without a calibration process which would require a large amount of data. This is done by using the pollutant nature of the catchment in terms of buildup and wash-off processes as the basis of measurements. Therefore, the translation procedure is an extension of the current estimation techniques which are typically complex and resource consuming. The use of a translation procedure is simple and based on the graphical estimation of parameters and tabular form of calculations. The translation procedure developed is particularly accurate in estimating water quality in the initial part of runoff events.