Thesis (Ph. D.)--University of Hawaii at Manoa, 2002. / Includes bibliographical references (leaves 414-437). Also available on microfiche.

A comparison of the performance of selected conceptual models of the rainfall-runoff process forms the central theme of this study and the comparison was conducted with three major objectives in mind. The first objective was to develop a conceptual model that could be used by practising hydrologists for the refinement and extension of historical streamflow records. The major requirements of the model were that it should be simple in structure and easy to operate and yet be flexible in terms of complexity of structure and input requirements as well as producing output at a level of accuracy that is competitive with that of the more complex models presently available. A comparison of the performance of the required model with that of other models formed an integral part of the development process. The second objective of the comparative study was to contribute to current knowledge of the criteria used in the selection of a suitable model for a particular application. There are, at present, no reliable guidelines to assist the hydrologist in selecting a suitable model from the wide range of models available and a comparative study would indicate the merits of various forms of model structure. The third objective is associated with the problems that arise when no streamflow data are available for model calibration. One approach is to calibrate the model in a nearby gauged catchment that the hydrologist regards as being 'hydrologically similar' and transferring the model parameter values to the ungauged catchment. Little is known about the feasibility of this parameter transfer process or about the choice of a model for such an application. The third objective was to test the feasibility of the parameter transfer process and to make use of the comparison of model performance to determine the model characteristics that are most suitable for the purpose

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.

A glacierized 24 km² watershed in the Coast Mountains of British Columbia was studied during the 1976 melt season in order to investigate the naturally occurring spatial and temporal variations of stream water chemistry. The chemical species measured were those that have been shown to be the major products of chemical weathering: calcium, magnesium, potassium, sodium, and silica. Detailed analysis of errors in field and laboratory procedures were an integral part of the research design and it was shown that errors on individual determinations were similar to those of university and government laboratories. The two major components of the research design were: 1) comparison of the chemistry of four major tributaries within the study area, and 2) an analysis of the temporal variability of stream chemistry at the basin outlet. The results of paired comparisons of tributary chemistry were consistent with geologic differences between sub-basins. For example, potassium concentration was greater in streams draining granodiorite than in a stream draining only quartz diorite, reflecting the lesser abundance of K-feldspar in quartz diorite. The highest solute concentrations were observed in spring water draining a metamorphic roof pendant while glacier meltwater had the lowest concentrations of all terrestrial water. Four models were investigated for describing the relationship between stream chemistry and stream discharge at the basin outlet. The best predictive model for calcium concentration (log Ca = a + b log Q, Ca = 10[sup a] Q[sup b]) explained 60% of the calcium variance. However, subsequent analysis showed that the unexplained variance contained information about temporal changes in runoff sources. In particular, the time-dependent behavior of the residual variance was interpreted as the result of an increase in the ratio of glacier meltwater to ground water discharge through the summer. Furthermore, the sub-basin approach in the research design made it possible to objectively identify the two glacierized sub-basins as the source of this phenomenon. All solutes behaved similarly except potassium which generally varied little through time or with changing discharge. This was attributed to the high availability of K⁺ in vegetation and soils and an apparent buffering of its concentration in the weathering zone. In a glacierized sub-basin almost lacking well-developed soils and forested slopes, potassium behaved more like the other solutes. All terrestrial water was shown to be in equilibrium with kaolinite in the Ca-plagioclase weathering system. Within the kaolinite stability field, water samples from different sources plotted in positions that were consistent with the availability of plagioclase, residence time, and the availability of C0₂ as a source of acidity during hydrolysis. / Arts, Faculty of / Geography, Department of / Graduate

No description available.

Thesis: Sc. D., Massachusetts Institute of Technology, Department of Civil Engineering, 1975 / Vita. / Bibliography: leaves 213-221. / Sc. D. / Sc. D. Massachusetts Institute of Technology, Department of Civil Engineering

Residential infill development and the associated increases in impervious cover and stormwater runoff have the potential to overwhelm aging infrastructure causing erosion, flooding, and ecological degradation of waterways. The lack of greenfield sites available for new development around urban centers coupled with a desire for maintaining a traditional neighborhood aesthetic drives residential infill and replacement of existing smaller homes by significantly larger structures, minimizing open space available for stormwater mitigation. An analysis of residential infill development trends in Fairfax County was performed to characterize the effects of intensified development. Development patterns were identified and assessed using digitized impervious cover data extracted from aerial imagery of the study area for six selected years from 2002 to 2015. The average annual increase in percent impervious area was computed to be 0.3%. Redevelopment was found to be mainly occurring in areas zoned as lower-density residential. The spatial distribution of redevelopment showed trends of clustered increases as opposed to isolated events. The hydrologic analysis performed revealed that from 2002 to 2015, there was an 8,930 m3 (7.2 acre-ft) increase in stormwater runoff volume, 38% of which is contributed to by runoff generated from development that is considered exempted from regulation in Fairfax County. Additionally, there was a 28 kg/year (62 lb/year) increase in total phosphorus loads attributable to the change in impervious cover due to residential development throughout the study area. The results of this study provide a quantitative basis for municipalities to amend policies regulating residential development and its associated stormwater management. / Master of Science

<p> This is the first study of the karst features found at Moira River karst. This study intends to investigate a number of different karst features of the area rather than concentrating on one highly specific problem. Hopefully this will enable the reader to appreciate the wide diversity of karst able to form within a small area such as Moira karst.</p> <p> The variation in karst features encountered at Moira River ranged from a relatively rare form of karst, called a draped karst, to dissolution patterns (scallops), found within a cave. The draped karst dominates much of the area and is formed by the preferential removal of thin, recessive limestone beds. The overlying, massive bedded unit remains and is "draped" over an underlying massive unit.</p> <p> The river plays a dominant role in the formation of karst features at Moira Karst. It floods quite frequently as evidenced by the number of runoff channels found in the area. The caves at Moira River karst have developed as a short cut across a bend in the river and are fully inundated when the river reaches high flow rates. Karst development does not extend much beyond a range of 300 m from either bank of the river and is concentrated on the east side of the river.</p> / Thesis / Bachelor of Science (BSc)

The operation and maintenance of highways contributes a variety of pollutants to surface and subsurface waters. Solids, heavy metals, nutrients, oil and grease, pesticides and bacteria can all be associated with highway runoff. Although the full extent of the effect of all these runoff constituents upon the quality of surrounding waters is not well defined, this study will mainly concentrate on nutrient contaminants (essentially phosphorus). The last decade has seen increasing efforts in research and development to abate contaminant discharges from highway runoff using a number of treatment facilities such as swale and detention/retention ponds. An evaluation of the effectiveness of these systems in removing phosphorus by physical, chemical and biological uptake is the aim of this research endeavor. This study represent the first step towards the determination of design criteria for swales and detention/retention ponds based on water quality improvement.

The overall goal of this research was to improve simulation of soil phosphorus (P) transport and transformations in GLEAMS 3.0, a non-point source model that simulates edge-of-field and bottom-of-root-zone loadings of nutrients from climate-soil-management interactions to assess management alternatives. The objectives of this research were to identify the state of the science for P transport and transformations, determine appropriate relationships for inclusion in GLEAMS, and determine if modifications to GLEAMS improved predictions of P loss in runoff, sediment, and leachate. The state of the science review revealed numerous equations available to predict dissolved P loss in runoff and leachate from a soil's nutrient status. These equations use a single variable to predict P loss and were developed for site-specific conditions based on empirical data. Use of these equations in GLEAMS is not reasonable as transport factors must also be considered when predicting P loss. Results from the sensitivity analysis showed that GLEAMS prediction of leached P were extremely sensitive to changes in the P partitioning coefficient (CPKD). Runoff PO₄-P output was slightly to moderately sensitive, sediment PO₄-P was moderately sensitive to sensitive, and sediment organic P was moderately sensitive to changes in CPKD whereas plant uptake of P was insensitive to slightly sensitive. The weakness of GLEAMS to estimate CPKD has been documented. Upon further investigation, it was determined that CPKD was highly over-estimated in GLEAMS as compared to measured values found during the literature review. Furthermore, this over-estimation caused under-estimation of the P extraction coefficient (BETA P); the value of BETA P remained constant at 0.10 and did not vary over the simulation period. Expressions for CPKD and BETA P were modified in GLEAMS. Data from three published studies (Belle Mina, Gilbert Farm, and Watkinsville) were used in the analyses of three modifications to GLEAMS: GLEAMS BETA P, GLEAMS CPKD, and GLEAMS BETA P+CPKD. GLEAMS BETA P investigated the change in BETA P as a function of soil clay content, GLEAMS CPKD attempted to improve GLEAMS' estimation of CPKD, and GLEAMS BETA P+CPKD assessed the combined effects of changes to BETA P and CPKD. Over the respective study periods, GLEAMS over predicted runoff PO₄-P for Belle Mina by 193 to 238% while under-predicting runoff PO₄-P at Gilbert Farm by 41% and Watkinsville by 81%. Sediment P was over-predicted by GLEAMS for Belle Mina by 225 to 233% and Gilbert Farm by 560%, while sediment P was under-predicted by 62% at Watkinsville. Leached PO₄-P was both over- and under-predicted by GLEAMS; Belle Mina was the only data set with observed leached P values. Simulation results from the model changes were inconclusive. There was no clear evidence supporting use of one model over another. Modifications increased predicted dissolved P in runoff and leachate, while decreasing predicted sediment-bound P in runoff. The original GLEAMS model best predicted runoff and leached PO₄-P at the Belle Mina sites. GLEAMS CPKD was the best predictor of runoff PO₄-P and sediment P at Gilbert Farm. GLEAMS BETA P+CPKD best predicted runoff PO₄-P at Watkinsville. Overall, the proposed improvements to GLEAMS did not improve GLEAMS predictions. In conclusion, GLEAMS should not be used for quantitative estimates of hydrology, sediment, and nutrient loss for specific management practices. As recommended by the GLEAMS model developers, GLEAMS should only be used to predict relative differences in alternative management systems. It is recommended that future research focus on developing a better correlation between CPKD, clay mineralogy and content, and organic matter content, as CPKD has been identified as a vital component of the GLEAMS P sub-model that requires further examination. / Master of Science