Stormflow generation was studied in a two square kilometre, sub-alpine, first-order basin tributary to Ryan River, which is in the Pacific Ranges of the Coast Mountains of British Columbia. Preliminary field work suggested that neither saturation overland flow nor subsurface stormflow were important mechanisms of stormflow generation Hortonian overland flow appeared to be dominant. The infiltrability of the soils dropped considerably during storm events. Three possible causes of this decline were considered initially: (1) a reduction in capillary gradients as wetting proceeds, (2) a textural contrast in the profile, and (3) air entrapment. All of the preceeding were rejected on the basis of more detailed observations. Instead, it was proposed that a water-repellent layer existed near the top of the soil profile. Laboratory experiments conducted on intact soil samples demonstrated that a repellent layer on the order of a few centimetres thickness did exist near the soil surface. The implications of this finding for infiltration and stormflow generation are discussed. / Arts, Faculty of / Geography, Department of / Graduate

The recession portion of the ephemeral stream hydrograph is modeled as a conceptual analog of the discharge from a single leaky reservoir. Physically, the reservoir may be considered to approximate that portion of the ephemeral stream channel that is flowing at the beginning of recession. The discharging reservoir is described by a continuity equation and by discharge-stage and storage-stage relations. No input is routed through the reservoir. It is assumed that initially (at the beginning of recession) the reservoir has water in storage. The discharge-stage relation for the reservoir is defined by the rating curve for the stream and storage-stage depends on reservoir configuration. A good agreement between observed and model curves is obtained by optimizing two parameters, reservoir leakage rate and initial storage, The agreement is most sensitive to changes in initial storage. Best parameter values are physically realistic and best reservoir configuration has leakage that varies directly with stage (depth) and storage that varies as the square of stage.

Data compiled from standardized procedures for width measurement at established streamflow gaging stations were used to develop a power-function relation between width in feet (W(A)_), and mean discharge in acre-feet per year (Q), for high-gradient perennial streams. Highgradient channels, which generally exhibit low variability for most factors influencing the width-discharge relation, were selected to indicate a standard exponent in the power-function equation. Flume data supported extrapolation of the high-gradient relation, Q = a w(A)¹•⁹⁸, through five orders of discharge magnitude. Further support for a standard exponent of the regression equation was provided by data from Kansas streams that had very silty beds and similar gradients, climate, and vegetation. Regression analysis of data from these streams gave an exponent of 2.01. Hence, a constant exponent of 2.0 was used for the width-discharge relation of all streams. To account for the effect of sediment on channel geometry, silt-clay percentages of the bed and bank material of 98 perennial streams of the western and midwestern United States were introduced into the standard width-discharge relation. Bed and bank cohesiveness, as indicated by silt-clay content, is considered a measure of channel competence. Narrowest streams for a specific mean discharge occur where channel competence, due to fine material and other variables including channel armoring and lush riparian vegetation, is greatest. Thus, at constant discharge, stream width varies inversely with both bed and bank silt-clay content. Multiple-regression analysis yielded the equation: Q = 2.0 w(A)²•⁰ (SC(bd))⁰•²² (SC(bk))⁰•⁵⁷ where SC(bd) and SC(bk) are percent silt-clay of bed and bank material, respectively. The average standard error of estimate for the relation is 58 percent, much of which is inferred to result from excessive width caused by bank erosion of historically recent flood events. Other causes of deviation from the relation include errors associated with the collection and analysis of data, climate and riparian vegetation, discharge variability, and armoring by coarse sediment sizes. Studies showing that stream channels are widened during periods of flooding suggest that most streams subsequently narrow toward an equilibrium width at normal discharges. Assuming that about one-sixth of the data sets, those exceeding one standard deviation, indicate streams too narrow owing to unrepresentative data or recently deficient runoff, the multiple-regression equation was modified to define channel equilibrium. For known conditions of mean discharge and sediment characteristics, an equilibrium width, W(eq) , can be calculated. Comparison with the measured width, W(A), defines the instability ratio, W(A)/W(eq) , The instability ratio identifies the degree to which channel width varies from assumed equilibrium, and ranges from 1.0 to 1.5 for most perennial streams. The ratio of suspended load to bed load appears to be a principal determinant of channel morphology, whereas sediment yield affects the rapidity with which channel healing can occur after widening by flooding. Greatest channel instabilities generally occur in sandchannel streams of arid to semiarid areas. In humid areas, lush vegetation, which encourages accretion of fine sediment sizes to bank material, induces channel stability. Low discharge variability, as shown by springs and regulated streams, generally results in low values of instability. Utility of the multiple-regression equation includes estimation of discharge from ungaged basins, and prediction of short-term changes in channel morphology resulting from altered supplies of water or sediment. Isolation of the influence of sediment on the width-discharge relation also permits consideration of the effects of other variables on channel shape.

The purpose of this study is to develop a method for predicting monthly flow duration curves for ungaged basins that are suitable for estimating average annual flow, and installed capacity and average annual energy generation at potential sites for hydropower development. The procedures were tested by developing monthly rainfall duration curves for five sample watersheds and then developing flow duration curves from the rainfall data. The methods were evaluated by comparing the predicted monthly flow duration curves to daily and monthly flow duration curves based on field data from the selected sites because a plant's potential energy output can be computed directly from a flow duration curve. The methods tested fit duration curves based on field data reasonably well and are suitable for preliminary evaluation of hydropower developments in ungaged basins.

No description available.

Thesis (M.S. - Hydrology)--University of Arizona. / Includes bibliographical references (leaves 84-85).

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

Thesis (M.S.)--University of Nevada, Reno, 2008. / "August, 2008." Includes bibliographical references (leaves 68-72). Online version available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 201-217). Also available on the World Wide Web.

Thesis (M.S.)--University of Tennessee, Knoxville, 2009. / Title from title page screen (viewed on Mar. 12, 2010). Thesis advisor: Qiang He. Vita. Includes bibliographical references.