Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains ix, 149 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 60-63).

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Thesis (Ph.D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 135-142).

Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1999? / Corrigenda pasted onto front end-paper. Bibliography: leaves 307-326.

Thesis (Ph. D.)--University of Adelaide, School of Civil and Environmental Engineering, 2006. / "October 2006." Includes bibliographical references (p. 261-270). Also available in print form.

Thesis (Ph. D.)--University of Washington, 1991. / Vita. Includes bibliographical references (leaves [162]-168).

Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 10, 2009). Includes bibliographical references.

Understanding the spatial and temporal dynamics occurring in headwater catchments enhances our ability to effectively manage the natural and unnatural inputs from the landscape to the stream. DOC is particularly important in northern peat dominated catchments, where concentrations in rivers have been increasing over recent decades. Due to the significant downstream impacts this increase has on the functioning of aquatic ecosystems and the quality of drinking water, it is vital to understand the tight coupling between the landscape and the stream. This study set out to explore the use of integrating high-frequency DOC data, stable isotopes and modelling as a novel way to increase our understanding of the hydrological and biogeochemical processes that control spatial and temporal DOC dynamics. By deploying in-situ FDOM sensors, across nested catchments, we captured 15 minute DOC dynamics. This yielded insights into seasonal, event and diel temporal variability, along with spatial variability. Results showed the utility of linking these DOC dynamics with stable isotopes and water ages, extracted from a tracer-aided runoff model. This allowed the main runoff generating processes, that transport the DOC from the sources to the stream, to be assessed, and showed the effects of hydrologic connectivity and antecedent conditions on DOC delivery. Incorporating modelling allowed the non-stationary hydrological processes influencing runoff generation, which cannot be easily measured by field techniques, to be evaluated. Overall, the findings of this thesis underline the utility of integrating highfrequency DOC data, stable isotopes and modelling to extract a highly informative dataset that helps produce a more complete symphony of the highly variable dynamics occurring in upland catchments. Such knowledge is crucial in order to effectively evaluate the influence of climate change on the water resources that both nature and humans so heavily depend on.

Hydrological responses vary from one catchment to another, depending on the nature of land use and cover changes. Modelling the hydrological responses to changes in land use and cover at different catchment spatial scales was the major focus of this study. This study assessed the hydrological responses attributed to changes in land use and extreme weather events resulting into increased sediment loading/concentration, rainfall-runoff generation/volume, streamflow fluctuation and modification of the river channel in the Malaba River Catchment, Eastern Uganda. The hydrological responses were assessed using hydrological models (IHACRES, SCS CN, and SHETRAN) to examine the effect of land use on soil physio-chemical properties susceptibility to rainfall-runoff generation and volume, frequency and severity of extreme weather events, changes in streamflow variations, sediment loading/concentration and river channel morphology. The preliminary study results showed that the frequency of extreme weather events reduced from 4-10 to 1-3 years over the catchment. The performance of the IHACRES model with a Nash-Sutcliffe Efficiency (NSE) of 0.89 showed that streamflow comparatively corresponded with the results obtained the drought indices in predicting the recorded events of severe drought (2005) and flood (1997). Changes in land use and cover types showed that the highest change in the gain of land was experienced from the agricultural land use (36.7 percent), and tropical forest (regeneration) (2.2 percent). The biggest losses in land were experienced in the wetlands (24.6 percent) and bushland and thickets (15.3 percent) land cover types. The SHETRAN model calibrated period had a NSE of 0.78 and 0.81 in the validation period showed satisfactory fits between the measured and simulated streamflow. The agricultural land use (crop growing) had a higher influence on the rainfall-runoff generation and increase in the streamflow than the tropical forest, and bushland cover types in the simulated period. Similarly, the curve number model estimated a comparatively higher surface rainfall-runoff volume generated from the agricultural land use (crop growing) (71,740 m3) than in the bushlands and thickets (42,872 m3) from a rainstorm followed by the tropical forest cover type. This was also reflected in the lower rates of saturated hydraulic conductivity from the agricultural land use (crop growing). The study also showed that human-induced sediment loading due to gold mining activities contributed a much higher impact on the concentration of suspended sediments and streamflow than sediments from rainfall-runoff from the sampled streams. The main contributor of human-induced sediments to the Malaba River were Nankuke River (130.6kg/annum), followed by Omanyi River (70.6kg/annum), and Nabewo River (66.8kg/annum). Human-induced sediment loading had a profound impact on the streamflow variations both in the dry and wet seasons from the sampled tributaries. Lastly, in regard to the effect of land use and cover types on the river channel morphology, tree plantation (cohesion=12, angle of internal friction=27) and bushland and thickets (cohesion=14, angle of internal friction=22) cover types had the most stable river banks compared to the wetland and agricultural land use and cover types that exhibited higher levels of sediment concentration.