Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xvii, 104 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Andy Ward, Dept.of Food, Agricultural, and Biological Engineering. Includes bibliographical references (p. 100-104).

No description available.

<p> In ephemeral streams, infrequent surface flow can be the main source of water that sustains plants throughout long dry periods. The objectives of this research are to: (1) explore seasonality of rainfall runoff in different channel types and (2) examine how runoff thresholds vary by channel type. The study area was two watersheds with areas of 188 km² and 323 km² on the Yuma Proving Grounds (YPG) in the Sonoran Desert near Yuma, Arizona. Eight tipping bucket rain gauges were installed to measure precipitation. Runoff was measured with 18 pressure transducers in five different channel types with different channel morphologies and contributing areas ranging from 0.002 km² to 225 km². Over approximately two years there were 11 to 48 rain events at the different rain gauges. Stream types with bedrock channels and small watershed areas between 0.005 km² and 0.015 km² produced runoff when the peak 60-minute precipitation intensity (I60) exceeded 4-6 mm hr^-1. At these sites, 17-25 percent of the rain storms generated runoff. I60 values of 5-9 mm hr^-1 produced runoff in streams with contributing areas of 0.021-0.061 km² on mid-Pleistocene piedmont surfaces covered by desert pavement. At these sites, 31-36 percent of rain events produced runoff. Streams incised into bedrock with some alluvium fill produced runoff at larger I60's of 13-18 mm hr^-1. Contributing areas for these sites were 0.8 km² to 2.2 km², and up to 10 percent of precipitation events at these sites produced flow. Precipitation thresholds for runoff generation in streams with contributing areas >3 km² were not clearly defined due to the influences of variable precipitation in upstream tributaries and transmission losses of streamflow through channel bed alluvium. For watersheds with &lt;3km², rain intensity thresholds increased with the log of catchment area, and as a result flow frequency tended to decrease with increasing catchment area.</p>

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 152-163). Also available via the Internet.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed May. 20, 2008). PDF text: x, 178 p. : ill. (some col.) ; 17 Mb. UMI publication number: AAT 3284241. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 92-95).

Thesis--Wisconsin. / Includes bibliographical references (leaves 96-99).

In urban areas with high amounts of impervious land cover, stormwater basins provide a valuable service by trapping and slowly infiltrating excess runoff which would otherwise impair streams. Stormwater basins also trap fine sediment suspended by runoff, which can lead to clogging of pore spaces needed for proper infiltration and cause the basin to fail. Basins require maintenance, but a thorough understanding of basin behavior is needed to find appropriate maintenance strategies. The goal of this study was to use multiple techniques – electrical resistivity tomography (ERT), ground-penetrating radar (GPR), sediment sampling, soil moisture sensors, and water level loggers – to assess stormwater basin failure and aid in the creation of targeted basin maintenance strategies. Three basins were selected for monitoring based on size and age: the Upper Moreland Middle School Basin (or “Betz”), the Ethel Jordan Memorial Park Basin, and the Lukens Park Basin. Five to six sediment cores were collected from each basin from depths down to 40 cm. Sediment data did not provide evidence for a layer of fine sediment at the basin surface. Basin sediments did not show consistent patterns with depth: Betz coarsened with depth, Ethel Jordan was relatively homogeneous, and Lukens fined with depth. Sediment at Betz and Lukens fined across the basin from inlet to outlet, but sediment from Ethel Jordan was more uniform across the basin. ERT was able to demonstrate differences in resistivity between the basins, as well as structure beneath the basins. The technique was most useful at Lukens, where buried stormwater chambers were identified, and Ethel Jordan, where rocky, high-resistivity portions of the basins were mapped. GPR used at Ethel Jordan showed strong reflected signals from the same region that displayed high resistivity values, helping to confirm the location of the subsurface features. Neither technique was able to demonstrate sediment heterogeneity. Time-lapse ERT surveying was employed at Betz to detect infiltration during storms. However, changing water levels and conductivity values made data inversion difficult and obfuscated any signal from infiltration. Furthermore, it was not apparent that any infiltration was occurring at Betz. Recession rates from water ponded in the basin were more rapid in the summer than in the winter, and were higher in Betz than in Ethel Jordan. Recession at Lukens was not calculated because the basin did not store water due to a broken riser pipe. Soil moisture sensors placed within basin were used to calculate infiltration rates. Rates could only be calculated at Lukens Park, as the subsurface was saturated at Betz and Ethel Jordan. The sensors demonstrated heterogeneity in infiltration rates throughout the basin and the adjacent land surface, as well as lower infiltration rates caused by vegetation. Basins showed no signs of failure based on the results of the monitoring techniques used, but did demonstrate variations in infiltration and recession behavior. While a concise maintenance plan could not be created, this study demonstrated the advantages of multiple monitoring techniques that can be used to improve maintenance strategies. / Geology

No description available.

<p> In order to make informed decisions in response to future climate change, researchers, policy-makers, and the public need climate projections at the scale of few kilometers, rather than the scales provided by Global Climate Models. The North American Regional Climate Change Assessment Program (NARCCAP) is such a recent effort that addresses this necessity. As the climate models contain various levels of uncertainty, it is essential to evaluate the performance of such models and their representativeness of regional climate characteristics. When assessing climate change impacts, precipitation is a crucial variable, due to its direct influence on many aspects of our natural-human ecosystems such as freshwater resources, agriculture and energy production, and health and infrastructure. The current study performs an evaluation analysis of precipitation simulations produced by a set of dynamically downscaled climate models provided by the NARCCAP program. The Assessment analysis is implemented for a period that covers 20 to 30 years (1970-1999), depending on joint availability of both the observational and the NARCCAP datasets. In addition to direct comparison versus observations, the hindcast NARCCAP simulations are used within a hydrologic modeling analysis for a regional ecosystem in coastal Louisiana (Chenier Plain). The study concludes the NARCCAP simulations have systematic biases in representing average precipitation amounts, but are successful at capturing some of the characteristics on spatial and temporal variability. The study also reveals the effect of precipitation on salinity concentrations in the Chenier Plain as a result of using different precipitation forcing fields. In the future, special efforts should be made to reduce biases in the NARCCAP simulations, which can then lead to a better presentation of regional climate scenarios for use by decision makers and resource managers.</p>