Pathogen contamination is a primary source of surface water quality impairment in the United States and modeling tools to predict concentrations of indicator organisms have utility for those involved in watershed management and ecosystem restoration, as well as public health and source and recreational water protection. This research evaluated the use of artificial neural networks (ANNs) for simulating concentrations of fecal indicator organisms in the surface waters of the Gates Brook and lower Charles River watersheds in Massachusetts. ANN model performance was assessed in terms of both the ability of the ANN models to accurately match observed indicator organism concentrations, as well as the ability of the models to correctly predict when a relevant water quality standard is violated due to exceedance of an indicator organism concentration. In addition to the fundamental question of ANN model performance, several other issues related to the development and implementation of the ANN models were explored, including the effects of different methods Of input selection and logarithmic transformation of data, the temporal transferability of the ANN models, and the potential for use of ANN models in ungaged watersheds. A comparison of ANN and ordinary least squares (OLS) regression models for fecal coliform prediction was also performed. In both watersheds, for all combinations of input parameters considered, values of average absolute percent error (AAPE) and root mean square error (RMSE) are high. When the model performance assessment is based on the ability to identify violations of a water quality standard, the impression of model performance is quite different. The best performing ANN models in each watershed are able to predict approximately 60% to 90% of the violations of the 200 CFU/100 mL standard, which is the fecal coliform standard for primary contact recreation in Massachusetts. The ANN models developed for Gates Brook show performance that is comparable to and, in some situations, slightly better than other ANN and regression models developed for indicator organisms and pathogens.

This dissertation is a composite of several studies. First, three of the most common fracture sampling techniques are tested against each other to evaluate the effectiveness of each method to adequately capture the properties of natural discrete fracture networks (DFNs). Numerical simulation is used to evaluate the single scanline, selection and multiple scanline methods in layered rocks. Using statistics from each of the techniques, DFNs are stochastically generated and compared to another network that represents the natural DFN. This model was built with the exact locations, sizes and orientations of fractures as the natural network. Porosity and permeability results reveal that the most effective method to use is the selection method because this method is consistent and performs as well as the other methods but with less expenditure of time and energy. Second, the influence of lithology and rock fabric on fracture attribute distribution in crystalline rock is assessed. Trace lengths, spacings and orientations of joints and foliation-parallel fractures (FPFs) are used to determine the potential influence of fracture type and distribution on the groundwater flow system. Results show that although both joints and FPFs are common, major orientations and spacings are different for both fracture types. Because FPFs possess identical trace lengths but narrower spacing than joints, numerical modeling experiments indicate that they play an important role in controlling the groundwater flow regime by enhancing the transmissive properties of rocks. Third, conceptual models of DFNs that have unique hydraulic character that are based on fracture configurations and properties are developed with the aid of numerical simulations. Sets of persistently parallel fractures are stochastically generated to assess the effects of fracture size and distribution, intensity, number of sets and intersection angle on the hydraulic properties of DFNs. Arbitrarily chosen class intervals of the ratio of DFN permeability to that of a single fracture are used to delineate DFNs with similar hydraulic character. Numerous graphs are created for use in the field to determine and delineate DFNs with distinct hydraulic character.

Hydrological and geochemical data was collected from a small area within the 7.32-km$\sp2$ Cadwell Creek drainage basin in west-central Massachusetts for a period of one year. The hydrologic monitoring network included a tipping-bucket rain gauge, soil-moisture and soil-temperature probes, and continuous water-level recorders to measure changing groundwater levels and stream stage. The geochemical sampling network consisted of precipitation and throughfall collectors, soil water collectors, shallow and deep groundwater monitoring wells, and stream sampling locations. Water samples were collected on a weekly or bi-weekly basis for the entire study period. Both the hydrologic and geochemical information collected during the study period indicated that the majority of water reaching the stream, both during periods of high water level and storm flow and during baseflow periods in the summer months, was derived primarily from the top meter or two of the shallow water-table aquifer. Deeper groundwater exhibited a substantially different chemistry from that in the top 1-2 meters of the aquifer. The geochemical evidence clearly indicated that deep groundwater never entered the stream, even during baseflow periods. Instead, the stream in the vicinity of the study site became dry in the summer. Comparison of groundwater and stream chemistry during periods of high water level clearly indicated that the water in the stream was derived almost solely from the shallow groundwater, with little or no contribution from more dilute precipitation and soil water. Silica concentration, as well as alkalinity and pH values, proved to be an important indicator of the origin of water entering the stream. Specific factors affecting the degree to which acidic precipitation is neutralized before entering surface water within this watershed are primarily hydrologic in nature. The amount of time that precipitation water is in contact with the geologic materials prior to entering the stream appears to determine the degree to which it is neutralized. In this case, the depth to the top of the water table is a controlling factor. Silicate weathering dominated cation exchange as a neutralization mechanism in this watershed, at least in the vicinity of the instrumented site.

No description available.

Several previous studies have compared design storms with continuous simulation results for the purposes of estimating flood frequency distributions. These previous studies were limited in scope to primarily urban single lumped catchments. This thesis attempted to perform a more detailed comparison of design storm and continuous simulation flood frequency distributions by extending the analysis to different basin types, as well as examining the effect of more complex watershed systems and storage elements (detention ponds). It was found that design storms could reasonably reproduce continuous simulation flood frequency distributions if an appropriate distribution and antecedent conditions were selected. Design storms were found to compare increasingly well to continuous simulation results in more complex watershed systems and through storage elements. / Thesis / Master of Applied Science (MASc)

Doctor of Philosophy / Department of Geography / Melinda Daniels / Great Plains rivers are unique systems that vary from large, continental scale, to small intermittent streams with grain sizes that range from bedrock to cobbles to silt. These rivers have been subject to widespread hydrologic alteration both within the channel and the watershed, which has resulted in an alteration in their hydrologic and geomorphic regimes. Although there is an acknowledgement of this alteration, to date there has not been a synthesis of the hydrology of Great Plains rivers or of their longitudinal morphologies. Chapters in this dissertation provide, to my knowledge, the first comprehensive analyses of the hydrology and morphology of Great Plains rivers over a range of spatial and temporal scales. In the first study, I found that there was no uniform pattern of hydrologic alteration throughout the Great Plains, which is likely attributable to variable system-specific reservoir management objectives, land use changes, and climatic regimes over the large area the Great Plains encompass. Results of this study are the first to quantify the widespread hydrologic alteration of Great Plains rivers following impoundment. In the second study, I found an apparent decoupling between local moisture conditions and streamflow in intermittent prairie streams. Results of this study used statistical models to identify relationships between flow intermittence, mean annual flow, and flood flow characteristics with moisture to characterize flow in an intermittent prairie stream. In the final study, I found that the downstream trends in hydraulic geometry and substrate characteristics of the Ninnescah River were consistent with the expected trends proposed by hydraulic geometry and substrate theories. However, there were points that deviated from the expected trends, most notably where a substantially large tributary enters the Ninnescah River and as the Ninnescah River approaches the Arkansas River, and causal explanations for these deviations were explored. Results of this study are, to my knowledge, the first of its kind to assess the longitudinal hydraulic geometry and substrate characteristics of a large sand-bed river over a large spatial scale. To our knowledge, there have been no comparable studies exist that attempted to describe hydrologic and geomorphic characteristics of prairie streams.

abstract: Soil moisture (θ) is a fundamental variable controlling the exchange of water and energy at the land surface. As a result, the characterization of the statistical properties of θ across multiple scales is essential for many applications including flood prediction, drought monitoring, and weather forecasting. Empirical evidences have demonstrated the existence of emergent relationships and scale invariance properties in θ fields collected from the ground and airborne sensors during intensive field campaigns, mostly in natural landscapes. This dissertation advances the characterization of these relations and statistical properties of θ by (1) analyzing the role of irrigation, and (2) investigating how these properties change in time and across different landscape conditions through θ outputs of a distributed hydrologic model. First, θ observations from two field campaigns in Australia are used to explore how the presence of irrigated fields modifies the spatial distribution of θ and the associated scale invariance properties. Results reveal that the impact of irrigation is larger in drier regions or conditions, where irrigation creates a drastic contrast with the surrounding areas. Second, a physically-based distributed hydrologic model is applied in a regional basin in northern Mexico to generate hyperresolution θ fields, which are useful to conduct analyses in regions and times where θ has not been monitored. For this aim, strategies are proposed to address data, model validation, and computational challenges associated with hyperresolution hydrologic simulations. Third, analyses are carried out to investigate whether the hyperresolution simulated θ fields reproduce the statistical and scaling properties observed from the ground or remote sensors. Results confirm that (i) the relations between spatial mean and standard deviation of θ derived from the model outputs are very similar to those observed in other areas, and (ii) simulated θ fields exhibit the scale invariance properties that are consistent with those analyzed from aircraft-derived estimates. The simulated θ fields are then used to explore the influence of physical controls on the statistical properties, finding that soil properties significantly affect spatial variability and multifractality. The knowledge acquired through this dissertation provides insights on θ statistical properties in regions and landscape conditions that were never investigated before; supports the refinement of the calibration of multifractal downscaling models; and contributes to the improvement of hyperresolution hydrologic modeling. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2018

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 142-155).

The Hydrological Simulation Program - FORTRAN (HSPF) in its personal computer version, release 10.10, was used to perform the hydrological simulation of a sub-watershed of the Occoquan River drainage basin. The sub-watershed selected was the Cub Run Watershed located in the northern area of the Occoquan River catchment. A model in the form of a User Control Input (UCI) file was prepared. The Cub Run Watershed was analyzed considering its geological, edaphic and weather characteristics, and segmented accordingly. The model was calibrated to adjust simulated results to observed data. Several calibration runs were executed and a final run was done considering a further segmented watershed. The simulation results were good even when not all the desired data could be found. The annual percent difference between the best calibration run and the observed results was 21.28%. The ten-month percent difference, excluding June and July, was 5.82 %. The first value is a fair result for hydrologic calibration, the second value is an excellent result for the same type of calibration. Additional segmentation did not further improve the results obtained during the best calibration run. Differences in the calibration when considering just a pervious segment or two segments (one pervious and one impervious) could be noted, indicating the importance of considering impervious surfaces for the simulation. HSPF reacted quite logically to variations in the calibration parameters and the results from those variations could be predicted beforehand. In summary, the PC version of HSPF was demonstrated to be a good management tool for the hydrological simulation of this watershed. / Master of Science

<p> Field studies of Cordilleran metamorphic core complexes indicate that meteoric fluids permeated the upper crust down to the detachment shear zone and interacted with highly deformed and recrystallized (mylonitic) rocks. The presence of fluids in the brittle/ductile transition zone is recorded in the oxygen and hydrogen stable isotope compositions of the mylonites, and may play an important role in the thermomechanical evolution of the detachment shear zone. Geochemical data show that fluid flow in the brittle upper crust is primarily controlled by the large-scale fault-zone architecture. </p><p> We conduct finite element numerical modeling of groundwater flow in an idealized cross-section of a metamorphic core complex. The simulations investigate the effects of crust and fault permeability fields on groundwater flow. Results show that fluid migration to mid- to lower-crustal levels is fault-controlled and depends primarily on the permeability contrast between the fault zone and the crustal rocks. High fault/crust permeability ratios lead to channelized flow in the fault and shear zones, while lower ratios allow leakage of the fluids from the fault into the crust.</p>