<p>In this dissertation, I explored the effects of vegetation type on ecosystem services, focusing on services with significant potential to mitigate global environmental challenges: carbon sequestration and groundwater recharge. I analyzed >600 estimates of groundwater recharge to obtain the first global combined analysis of groundwater recharge and vegetation type. Using a regression model, I found that vegetation was the second best predictor of recharge after precipitation. Recharge rates were lowest under forests, intermediate in grasslands, and highest under croplands. The differences between vegetation types were higher in more humid climates and sandy soils but proportionately, the differences between vegetation types were higher in more arid climates and clayey soils. My extensive field estimates of recharge under paired vegetation types in central Argentina and southwestern United States provided a more direct test of the relationships between vegetation and recharge. The field data confirmed the strong influences of vegetation and its interactions with abiotic factors on recharge observed in the synthesis. The results indicate that vegetation shifts have a proportionately larger potential to affect recharge in more arid climates and clayey soils.</p><p>At the same study systems, I compared my field estimates of recharge to organic carbon stocks (in biomass, litter and soil) under the different vegetation types to evaluate tradeoffs between carbon sequestration and groundwater recharge as affected by vegetation shifts. To determine net values of vegetation shifts, I combined the changes in carbon and water with reported economic values of the ecosystem services. Based on physiological tradeoffs between photosynthesis and transpiration in plants, I hypothesized that vegetation promoting carbon storage would reduce recharge and vice versa. Changes in water and carbon services were inversely proportional, with rain-fed cultivation increasing groundwater recharge but decreasing carbon storage compared to the grasslands they replaced whereas woody encroachment did the opposite. In contrast, cultivated plots irrigated with ground water decreased both ecosystem services. Higher precipitation and clay content both exacerbated changes in carbon storage with grassland conversions, whereas higher precipitation accentuated, but higher clay content diminished, those in recharge. Regardless of the nature of vegetation shift, most of the net values of grassland conversions were negative, with the shifts representing increasing costs in the following order: woody encroachment, rain-fed cultivation and irrigated cultivation. Values of changes in carbon were greater in magnitude than those of recharge, indicating that establishment of carbon markets may drive land-use changes in grasslands over water markets.</p><p>Lastly, I examined the effects of changes in subsurface hydrology resulting from grassland conversion to croplands on soil inorganic carbon stocks in the same U.S. study system. I observed significantly lower inorganic carbon stocks under both rain-fed and irrigated croplands compared to the grasslands they replaced. The losses were visible to past 6 m depth in the soil profile and were uncharacteristically rapid for the carbon pool that is considered to be relatively inert. Based on the negative relationship between the inorganic carbon stocks and recharge rates and higher estimated exports of bicarbonates in recharge under croplands, I concluded that increased recharge with cultivation resulted in dissolution and leaching of grassland soil carbonates. Ecosystem services and their relationships to biotic and abiotic factors quantified here will further our understanding of the tradeoffs and interactions between the two services through vegetation shifts.</p> / Dissertation

The capability of radar measured rainfall to enhance the simulation of storm hydrographs was assessed. Six rainfall events which occurred in 1986 and 1987 over an 8.13 km$ sp2$ agricultural watershed in south-western Quebec were used in model simulations. Radar measured rainfall rates were calibrated using measurements from a single tipping-bucket raingauge located at the study site. / A deterministic, event-based model, HYMO, was used to simulate streamflow using radar and gauge measured rainfall. The model utilized two rainfall abstraction techniques, i.e. the SCS Curve Number method and the Green-Ampt infiltration equation. Simulated streamflow hydrographs were compared with observed storm flows. / For short duration, high intensity, simple rainfall events, there were minor improvements in hydrograph simulations when calibrated radar measured rainfalls were input to the model, compared to tipping-bucket raingauge measurements. Complex, low intensity storms were poorly simulated by the model using either rainfall data source. Neither rainfall abstraction method proved consistently superior.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23855号 / 工博第4942号 / 新制||工||1772(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 立川 康人, 教授 中北 英一, 講師 萬 和明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Corrigenda pasted onto front end-paper. / Bibliography: leaves 307-326. / xvii, 326 leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A study was undertaken of erosion and sedimentation in a catchment in South Australia. An erosion and sedimentation model was developed and interfaced with the existing digital terrain models called TAPES-C and THALES, to estimate soil erosion and deposition in Sauerbier Creek catchment. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1999?

Corrigenda pasted onto front end-paper. / Bibliography: leaves 307-326. / xvii, 326 leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A study was undertaken of erosion and sedimentation in a catchment in South Australia. An erosion and sedimentation model was developed and interfaced with the existing digital terrain models called TAPES-C and THALES, to estimate soil erosion and deposition in Sauerbier Creek catchment. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1999?

Hydrological observations are characterised by wet and dry cycles, a characteristic that is termed hydrological persistence. Interactions between global climate phenomena and the hydrological cycle result in rainfall and streamflow data clustering into wetter and drier states. These states have implications for the management and planning of water resources. Statistical tests constructed from the theory of wet and dry spells indicate that evidence for persistence in monthly observations is more compelling than at an annual scale. This thesis demonstrates that examination of monthly data yields spatially - consistent patterns of persistence across a range of hydrological variables. It is imperative that time series models for rainfall and streamflow replicate the observed fluctuations between the climate regimes. Monthly time series are generally represented with linear models such as ARMA variants ; however simulations from such models may underestimate the magnitude and frequency of persistence. A different approach to modelling these data is to incorporate shifting levels in the broader climate with a tendency to persist within these regimes. Hidden Markov models ( HMMs ) provide a strong conceptual basis for describing hydrological persistence, and are shown to provide accurate descriptions of fluctuating climate states. These models are calibrated here with a full Bayesian approach to quantify parameter uncertainty. A range of novel variations to standard HMMs are introduced, in particular Autoregressive HMMs and hidden semi - Markov models which have rarely been used to model monthly rainfall totals. The former model combines temporal persistence within observations with fluctuations between persistent climate states, and is particularly appropriate for modelling streamflow time series. The latter model extends the modelling capability of HMMs by fitting explicit probability distributions for state durations. These models have received little attention for modelling persistence at monthly scale. A non - parametric ( NP ) HMM, which overcomes the major shortcomings of standard parametric HMMs, is also described. Through removing the requirement to assume parametric forms of conditional distributions prior to model calibration, the innovative NP HMM framework provides an improved estimation of persistence in discrete and continuous data that remains unaffected by incorrect parametric assumptions about the state distributions. Spatially - consistent persistence is identified across Australia with the NP HMM, showing a tendency toward stronger persistence in low-rainfall regions. Coherent signatures of persistence are also identified across time series of total monthly rainfall, numbers of rain - days each month, and the intensities of the most extreme rain events recorded each month over various short durations, illustrating that persistent climate states modulate both the numbers of rain events and the amount of moisture contained within these events. These results provide a new interpretation of the climatic interactions that underlie hydrological persistence. The value of HMMs to water resource management is illustrated with the accurate simulation of a range of hydrologic data, which in each case preserves statistics and spell properties over a range of aggregations. Catchment - scale rainfall for the Warragamba Reservoir is simulated accurately with HMMs, and rainfall - runoff transformations from these simulations provide reservoir inflows of lower drought risk than provided from ARMA models. / Thesis (Ph.D.)--School of Civil and Environmental Engineering, 2006.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2007. / Härtill 5 uppsatser.

Thesis (Ph.D.)--McMaster University (Canada), 1996. / Source: Dissertation Abstracts International, Volume: 57-10, Section: B, page: 6146. Adviser: M. K. Woo.

Thesis (Ph. D.)--University of Adelaide, 1995. / Includes bibliographical references (p. 474-514).

Thesis (Ph. D.)--University of Newcastle, 1999. / Department of Civil, Surveying and Environmental Engineering. Includes bibliographical references (leaves 246-255). Also available online.