Many environmental studies of water transport through the vadose zone require a field determination of saturated hydraulic conductivity. The purpose of this dissertation is to analyze the reliability of existing methods to determine saturated hydraulic conductivity, K(s), in the vadose zone from constant head borehole infiltration test data. In methods developed by the U. S. Bureau of Reclamation [USBRI, and in lesser known ones, K(s) is computed knowing the height of water in the borehole, length open to the formation, borehole radius, distance above the water table, and steady flow rate. The mathematical formulas on which these methods rest are derived on the basis of numerous simplifying assumptions. The free surface approach is used as the conceptual model of flow from a borehole. Results of numerical simulations are used to compare with the analytical solutions. Simulations with a steady-state finite element computer program, FREESURF, show that the Nasberg-Terletskata solution most closely approximates flow from a borehole with the free surface approach. The influence of capillarity is simulated for saturated-unsaturated porous media in four soils using a finite element computer program, FLUMP, and an integrated finite difference program, TRUST. Contrary to what one finds with the free surface approach, only a small portion of the flow field near the borehole is saturated at steady-state and the cross sectional area normal to the flow path increases with depth below the borehole. For deep water table conditions in fine textured soils, values of K(s) computed using the USBR open-hole equations may be more than 160% greater than the true values; and in coarse sands the USBR solutions may under-estimate the actual value by more than 35%. Mostly because of the influence of unsaturated soil properties there is no unique relationship between K(s), borehole conditions, and steady flow rate, as implied in the analytical solutions. Steady-state simulations demonstrate that existing solutions for borehole infiltration tests in anisotropic or nonuniform soils may also lead to significant errors. Time dependent simulations show that the time to reach a steady flow rate may be more than several days in very dry, low-permeable soils. The time to reach a steady flow rate can be significantly reduced by decreasing the open area between the borehole and formation while increasing the height of water in the borehole. Two methods are proposed to minimize the time, water volume requirements, and cost of conducting constant head borehole infiltration tests. Simulations show that a plot of the inverse of flow rate versus logarithm of time departs from a straight line after about 80% of the steady rate is achieved for various soil and borehole conditions; the steady rate is approximately 0.8 times the rate at the break in slope. In the second method flow rate is plotted versus the inverse of the square root of time and the steady rate is estimated within about 10% by linear extrapolation of early time measurements. USBR field data generally support this linear relationship. Two empirical equations are proposed to compute K(s). The first is applicable for a range of borehole conditions and approximately accounts for capillary effects with a single parameter. The second applies if the height of water in the borehole is I meter, and is based on the time to reach 80% of the steady rate and saturation deficit of the field soil.

The Rodeo-Chediski Wildfire the largest in Arizona's history at the time of burning damaged and disrupted ecosystems resources and functioning in a largely mosaic pattern throughout the ponderosa pine (Pinus Ponderosa) forests exposed to the burn. Impacts of this wildfire on ecosystems resources and functioning were studied from shortly after the cessation of the wildfire in late summer of 2002 through the spring of 2007 on two previously instrumented watersheds located on sandstone derived soils within the burn. One watershed was burned by a high severity (stand-replacing fire), while the other watershed burned in a low severity (stand-modifying) fire. This dissertation focuses on the effects fire severity had on watersheds resources and functioning in terms of the tree overstories, herbaceous understories, large and small mammals, avifauna, hydrologic functioning, soil water repellency, hillslope soil movement, and fuel loadings. The results of these studies indicated the cumulative impacts incurred to ecosystem resources, hydrologic functioning, and flammable fuels were much greater on the watershed exposed to the high severity (stand-replacing) fire. It is anticipated that the overall ecological and hydrologic function on the watershed burned by a high severity will not approach pre-fire conditions for many years. The watershed burned at a low severity, however, was approaching pre-fire conditions nearly five years after fire and is expected to be recovered within the next few years.

Hydrologic catchment response varies in time. The goal of this dissertation is to investigate how and why it varies and what controls these variations. In order to tackle these questions the first step is to develop a method that permits the capturing of the temporal variation of transit time distributions (TTDs). To this end, the established transfer function-convolution approach using time series of stable water isotopes was modified so that it is now able to determine variable mean transit times (mTTs). The type and the shape parameter of the transfer function also vary in time. We found that antecedent moisture content, saturated hydraulic conductivity, soil depth and subsequent precipitation intensity are all potential controls. We propose a dimensionless number that integrates these controls and relates available storage to incoming and outgoing water fluxes in combination with information on antecedent moisture conditions to predict TTD type and shape. The individual TTDs for every time step produced by this model can be superimposed, summed and normalized to create a classification tool for catchments that is based on its general response behavior to precipitation events: the master transit time distribution. With this model in hand the hydrologic response for three consecutive monsoon seasons in ten nested subcatchments was examined. It was found that the major response controls were changing between the years in accordance with three hydrologic response modes. The mTT correlated most strongly with soil depth in the first year, with hydraulic conductivity in the second year and with curvature in the third year. These variations were produced by differences in precipitation patterns that led to differences in soil saturation and consequently to different dominant flow processes: in the first year most of the water left the catchment via fast flow paths (macropore flow, overland flow), in the second year shallow subsurface flow in the soil matrix was more dominant and in the third year most outflowing water derived from slow base flow. To better predict hydrologic catchment response we propose to apply a dimensionless number to determine the catchment response mode for every time step before selecting the appropriate response control.

The HYDROPAC model was developed to improve the technology transfer from the science of hydrology to environmental planning disciplines by initiating advanced spatial analysis techniques for predicting rainfall-runoff relationships. This model integrates the Soil Conservation Service (SCS) equations for calculating runoff and a Geographic Information System (Map Analysis Package) in a framework that allows the simulation of runoff processes over a digital elevation model. The simulations are done in discrete time steps allowing the generation of a hydrograph at any desired point in the watershed and the overland flow patterns are displayed in maps. This framework addresses some of the current limitations of hydrologic model for stormwater management planning in terms of capabilities for analysis and communication of results. This manuscript describes the methods used to develop the framework of the HYDROPAC model and its usefulness for analyzing potential runoff problems during the planning process.

A physically-based, user friendly, hydrologic computer simulation model was developed for pinyon-juniper woodland watersheds. The data requirements are minimum, requiring vegetation conditions, basic soil survey information, and daily values for precipitation and temperature. The model predicts runoff from cleared and uncleared watersheds by simulating hydrologic processes on a daily basis. The model was tested with data from small pinyon-juniper watersheds in central Arizona. A crack-forming vertisol was the dominant soil type, and a special feature for addressing its effects on runoff was included. No significant difference between predicted and observed annual runoff was found at the ninety-five percent confidence level.

The research project described in this dissertation studies the modelling techniques employed for the Mlazi River in the context of flood analysis and flood forecasting in order to model flood inundation. These techniques are applicable to an environment where there is uncertainty due to a lack of historical input data for calibration and validation purposes. This uncertainty is best explained by understanding the process and data required to model flood inundation. In order to model flood inundation in real time, forecasted flood flows would be required as input to a hydraulic river model used for simulating flood inundation levels. During this process, forecasted flood flows would be obtained from a flood-forecasting model that would need to be calibrated and validated. The calibration process would require historical rainfall data correlating with streamflow data and subsequently, the validation process would require real time streamflow data. In the context of the Mlazi Catchment, there are only two stream gauges located in the upper subcatchments. Although these stream gauges have recorded data for 20 years, the streamflow data does not correlate with disaggregated daily rainfall data, of which there are records for at least 40 years. Therefore it would be difficult to develop the forecasting model based on the rainfall and streamflow data available. In this instance, a more realistic approach to modelling flood inundation involved the integration of GIS technology, a physically based hydrological model for flood analysis, a conceptual forecasting model for real time forecasting and a hydraulic model for computation of inundation levels. The integration of modelling techniques are better explained by categorising the process into three phases: Phase 1 Desktop catchment modelling: A continuous, physically based simulation model (HEC-HMS Model) was set up using GIS technology. The model applied the SCS-UH method for the estimation of peak discharges. Synthetic hyetographs for various recurrence intervals were used as input to the model. A sensitivity analysis was implemented and subsequently the HEC-HMS model was calibrated against output SCS-UH method and peak discharges simulated. The synthetic hyetographs together with results from the HEC-HMS model were used for validation of the Mlazi Meta Model (MMM) used for real time flood forecasting. Phase 2 Implementation of the Inundation Model: The hydraulic model (HEC-RAS) was created using a Digital Elevation Model (DEM). A field survey was conducted for the purpose of capturing the roughness coefficients and hydraulic structures, which were incorporated into the model and also for the confirmation of the terrain cross sections from the DEM. Flow data for the computation of levels of inundation were obtained from the HEC-HMS model. The levels of inundation for the natural channel of Mlazi River were simulated using the one dimensional steady state analysis, whereas for the canal overbank areas, simulation was conducted for unsteady state conditions. Phase 3 Creation of the Mlazi Meta Model (MMM): The MMM used for real time flood forecasting is a linear catchment model which consists of a semi-distributed three reservoir cell model (Pegram and Sinclair, 2002). The MMM parameters were initially adjusted using the HEC-HMS model so that it became representative of the Mlazi catchment. This approach sounds unreasonable because a model is being validated by another model but it gave the best initial estimate of the parameters rather than using trial and error. The MMM will be further updated using record radar data and streamflow data once all structures have been put in place. The confidence in the applicability of the HEC-HMS model is based on the intensive efforts applied in setting it up. Furthermore, the output results from the calibrated HEC-HMS model were compared with other reliable methods of computing design peak discharges and also validated with frequency analysis conducted on one of the subcatchments. / Thesis (M.Sc.)-University of Natal, Durban,2003.

Advancements in computation and development of physically based hydrologic models to simulate complex vadose zone scenarios helped the research community to evaluate different scenarios easily compared to long-term field experiments. However, some field data collection is necessary to obtain input data such as soil properties, water usage and land management practices to validate the model performance specific to the site. Data obtained from field experiments conducted in 2011 at Hespler farms, Winkler, MB was used in this research for model calibration and validation. The hydrologic model, HYDRUS (2D/3D) was evaluated using parameters such as visual and statistical analysis. Model evaluation during the calibration and validation stage gave RMSE values of 0.019 and 0.015 cm3 cm-3; PBIAS values of -1.01 and -0.14, respectively, suggesting that the model was efficient in simulating soil water content similar to the field observed data. The validated models were then used to simulate outcomes for different scenarios such as 30-year rainfall data (1986 – 2015), different soil physical properties, and drainage system design parameters. Models simulating free drainage predicted lower soil water content compared to controlled drainage leading to 6 – 60 more trafficable days for 8 m spacing and 0.9 drain base depth. Free drainage predicted 8 – 110 additional trafficable days compared to controlled drainage for 15 m spacing and 1.1 drain depth. Heavier than normal rainfall events caused high water contents leading to a few years with a very low to no trafficable days under controlled drainage conditions. The comparisons are presented based on models using free drain conditions. Models with 8-m drain spacing predicted a 1 to 10-day increase in the number of trafficable days compared to the 15-m drain spacing. Drains placed at a base depth of 1.1 m below the soil surface predicted 4 - 40 more trafficable days compared to those installed at a base depth of 0.9 m. / October 2017

This study is focused on the evaluation of selected rainfall-runoff episodes in terms of temporal and spatial distribution of rainfall and runoff in the upper basin of the Blanice River. HEC - HMS model with two variants of spatial discretization was used to achieve the results of the holistic approach. The main input data was quantitative precipitation estimation, which better assessed the spatial variability of rainfall fields than interpolated ground measurements. The model simulated five episodes. Contrary to expectations, southern headstream area of the basin showed lower coefficient of runoff in comparison with its northern part. Precipitation cores of epizods occurred over the northern part of the basin at the outlet. Outputs from the model were evaluated in relation to measurements carried out in the experimental basin Zbytiny. Key words: Blanice River, HEC-HMS, hydrologic modeling, quantitative precipitation estimation

Master of Science / Department of Computing and Information Sciences / Mitchell L. Neilsen / In recent years, headline news has been overwhelmed with stories about dam and levee failures including the 2005 levee breaches in New Orleans and the 2006 Kaloko Damfailure in Hawaii that resulted in seven deaths. Since 2000, state and federal agencies have reported 92 dam failures in the United States to the National Performance of Dams Program. Incidents such as these have brought both national and worldwide attention to the need for improved flood warning systems and breach prediction tools for dam embankment and levee failures. (G. J. Hanson, 2010) IESIMBA 2012 is an upgraded version of SIMBA, which has been upgraded from VB6 to C#.NET. The Microsoft Windows-based SIMplified Breach Analysis software (SIMBA) was developed by the USDA Agricultural Research Service in cooperation with Kansas State University. The software was developed for the purpose of analyzing internal erosion, earth embankment breach test data and extending the understanding of the underlying physical processes of breach of an overtopped earth embankment. It is a research tool that is modified routinely to test the sensitivity of the output to various sub-models and assumptions. This software is a test version for use in validation testing of the simplified breach model based on stress and mass failure driven headcut movement. It runs under Microsoft Windows 98SE, Windows 2000, NT, XP, or Vista. The following Input Screens are used to guide the user through development of input data sets.  Model Properties , Dam Profile , Structure Table, Spillway Rating and Hydrograph Data After an input data set has been entered, the data is saved and simulation can be performed on the data stored in memory at any time by selecting Build option. Input and output files are stored in a fixed ASCII text format. The results of the simulation can be viewed in graphical format which are of interest to the researchers at Oklahoma State University, Stillwater by selecting View option.

Este trabalho compreende a modelagem hidrológica da bacia hidrográfica do rio Muriaé (BHRM). As simulações hidrológicas foram realizadas com o modelo hidrológico TOPMODEL com medições de precipitação de estimativa de vazão da rede telemétrica da Rede Hidrometeorológica Nacional (RHN). Utilizou-se também as respectivas estimativas de precipitação por satélite com o método CMORPH, e a análise de precipitação integrada entre a precipitação medida pela telemetria e a estimada por satélite por meio da análise objetiva estatística (ANOBES). A calibração e a validação do modelo TOPMODEL foram realizadas para eventos hidrológicos entre 2016 e 2018. A calibração do modelo TOPMODEL com as séries de dados de precipitação acima foi avaliada por meio do coeficiente de Nash-Sutcliffe (NSE), que variou entre 0,7 e 0,9. A validação do modelo TOPMODEL com séries independentes resultou em NSE de -0,8 a 0,3. Este resultado em grande parte se deve ao pequeno número de eventos hidrológicos desde o início das medições telemétricas na BHRM. O TOPMODEL também foi utilizado para simular vazões em séries com período anual entre 2009 e 2013. A calibração e validação com séries anuais resultaram em NSE ~ 0,6. Notadamente, as simulações com CMORPH tendem a subestimar as vazões, enquanto que com ANOBES o desempenho foi melhor, em especial para períodos de cheia. Portanto, os resultados sugerem a aplicabilidade do modelo TOPMODEL para simulações hidrológicas da Bacia do Rio Muriaé, com os melhores resultados obtidos quando a modelagem iniciou em um período de estiagem e o dado de precipitação representou a variabilidade espacial da chuva. / This study comprises the hydrological modeling of the Muriaé river basin. Hydrologic simulations were performed with the TOPMODEL hydrological model, with precipitation measurements and discharge estimation from the Brazilian Hydrometeorology Network (RHN). It was also used satellite precipitation estimates with the CMORPH method, and the integrated precipitation analysis between the precipitation measured by the telemetry and the estimated by satellite through objective statistical analysis (SOAS). The calibration and validation of the TOPMODEL model were performed for hydrological events between 2016 and 2018. The calibration of the TOPMODEL model with the above precipitation data series was evaluated using the Nash-Sutcliffe coefficient (NSE), which ranged from 0,7 and 0,9. Validation of the TOPMODEL model with independent series resulted in NSE from -0,8 to 0,3. This result is largely due to the small number of hydrological events since the beginning of telemetry measurements at the Muriaé river basin. TOPMODEL was also used to simulate flows in series with annual period between 2009 and 2013. Calibration and validation with annual series resulted in NSE ~ 0.6. Notably, CMORPH simulations tend to underestimate flow rates, while with SOAS the performance was better, especially for flood periods. Therefore, the results suggest the applicability of the TOPMODEL model for hydrological simulations of the Muriaé river basin, with the best results obtained when the modeling started in a drought period and the rainfall data represented the spatial variability of the rainfall.