<p> Satellite data from GOES and LANDSAT where evaluated as a source of information for hydrologic distributed models applied to large watersheds. Three basins within the Llanos area of the Orinoco River basin, Venezuela, were selected as study areas. The specific objectives of the study were; (1) To test the applicability of meteorological satellite data for improving information on the temporal and areal distribution of precipitation,as well as estimates of amount over large areas. (2) To investigate photographic and digital LANDSAT data as a source of land surface information for hydrologic distributed models. The satellite and ground data used in this research were: (1) GOES WEFAX electrostatic facsimiles, (2) LANDSAT photographic and digital data, (3) Reports and maps on soil studies by Desarrollo Industrial Agricola C.A (1958) and Comerma and Luque (1971). </p> <p> The analysis of the data was carried out by visual analysis on the photographic products of GOES and LANDSAT using r·egular photo-interpretation techniques. GOES photographic data allowed the analysis of temporal and areal distribution of precipitation over large areas. Follansbe's (1973) method for estimating precipitation using satellite imagery was found potentially applicable to hydrologic distributed models. Variations to the method are suggested. </p> <p> The visual analysis of a single LANDSAT image allowed the mapping of broad land-cover classes and some soil characteristics in the study area. Analysis of the multidate imagery was found very useful in detecting seasonal and non-seasonal changes. </p> <p> Digital analysis of LANDSAT data was carried out on the Image 100 system at the Canada Centre for Remote Sensing in Ottawa. Contrast stretched images and breakpoint enhancement supervised and unsupervised classifications were produced.The results showed that LANDSAT digital analysis either by unsupervised or supervised classification can be used for the extraction of land-use/land-cover information for application in hydrologic distributed models. </p> / Thesis / Master of Arts (MA)

Accurately measuring denitrification in stochastic floodplains, particularly the leveed and unleveed reaches of the Mississippi River basin, requires innovative experiments. To replicate hydraulic variability ranging from overland flooding to groundwater exfiltration in floodplain wetlands, I incubated sediment cores collected from four field sites across the Dogtooth Bend of the middle Mississippi River; pairing novel deep injection (Graphic Abstract Fig. A, left) with traditional surface delivery (Graphic Abstract Fig. A, right) of both oxic and anoxic Mississippi River water. In sandy sediments with unconstrained flux of nutrients, denitrification more than doubled across a range from 192 to 429 mg N m-2 day-1 in a linear anoxic-injection hierarchy of anoxic deep > anoxic surface > oxic deep > oxic surface treatments. In contrast, for incubations in diffusion-limited clay sediments, injection type made no difference; however, in anoxic conditions denitrification rates were as high as 435 mg N m-2 day-1 compared to oxic incubations at 187 mg N m-2 day-1. This methodology reveals the magnitude of diverse denitrification rates spanning different hydrologic conditions (Abstract Fig. B) and the mediation of denitrification by sediment type. These findings provide quantified bounds to inform resource management decisions regarding what areas should be selected for protection or hydrologic reconnection to best facilitate nutrient processing services like denitrification under varying hydrologic conditions.

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At Crabby Creek, an urbanized watershed in northeast Chester County, Pennsylvania, an NaCl tracer test was conducted in 2010 to assess changes in hyporheic flow from a 2009 tracer test around the same stream restoration J-Hook. This project compares the 2009 and 2010 tracer test breakthrough curves and geophysical time-lapse resistivity surveys. This project also compares elevation cross sections and tile probing from 2009 and 2010, both measured upstream and downstream from the J-Hook. To confirm areas of lingering tracer seen in the time-lapse resistivity profiles, sediment cores using the freeze core method were taken to measure pore water for tracer. This project also measured diurnal temperature flux through the streambed at several locations along the sample site to model vertical water and heat flux. The breakthrough graphs constructed from the conductivity of the well water samples shows similar hyporheic flow characteristics from 2009 to 2010. The time-lapse resistivity profiles show an area of lingering tracer upstream from the J-Hook in 2010 that is similar in shape and location to an area upstream from the J-Hook in the 2009 profiles. However, an area of lingering tracer downstream from the J-Hook present in 2009 as a round feature on the profile is now a thin linear feature. The freeze cores show tracer present in the pore water after the end of the tracer injection in the stream sediment, confirming areas of lingering tracer seen in the time-lapse resistivity profiles. The grain size analysis of the freeze cores and the comparison to the 2009 cores taken at Crabby Creek show similar grain size distribution upstream from the J-Hook. Downstream from the J-Hook the grain size analysis shows a redistribution of sediment. Upstream from the J-Hook the tile probe shows both shallower and deeper bedrock, a redistribution of sediment but no net erosion. Downstream from the restoration structure, however, the tile probe data show a sediment loss of 20 cm. Elevation cross section surveys from 2009 and 2010 confirm what the tile probing found, a loss of sediment downstream but not upstream from the J-Hook. Temperature modeling of heat flux through the sediment shows that the diurnal temperature distribution can be accounted for without vertical flux. Thus, the immobile regions upstream and downstream from the J-Hook seem to be related to sediment distribution rather than hydrologic gradient differences. The significance of this study shows the need to use multiple techniques to characterize the immobile zone as a part of hyporheic flow. The immobile zone is an important area of chemical reactions in the streambed. At Crabby Creek the central J-Hook inhibits net erosion patterns upstream from the structure, allowing for the continued presence of an immobile zone. Downstream from the central J-Hook the erosion of the streambed sediment led to a decrease in size and location of the immobile zone. The disturbance of sediment around restoration structures influences the development of a healthy hyporheic flow and needs to be studied for future restoration of impaired streams and riparian corridors. / Geology