Workshop on computer applications in water management: proceedings of the 1995 workshop

Compiled and edited by L. Ahuja, J. Leppert, K. Rojas, E. Seely.Also published as: Great Plains Agricultural Council publication, no. 154.Includes bibliographical references.Presented at the Workshop on computer applications in water management: proceedings of the 1995 workshop held on May 23-25, 1995 at Colorado State University in Fort Collins, Colorado

Geoarcheological Investigations of Wetland Cell D Within the Dallas Floodway Extension Project Area, Dallas, Texas

The Dallas Floodway Extension project is designed to provide flood damage reduction and environmental restoration within the Trinity River flood plain between the Corinth Street Viaduct and Loop 12. The U.S. Army Corps of Engineers, Fort Worth District, contracted with Geo-Marine, Inc., to conduct an archeological assessment of the proposed Wetland Cell D. The archeological assessment was to identify any potential archeological sites that may be eligible for inclusion in the National Register of Historic Places and to provide an assessment of the potential for buried landforms in the project area that may have intact archeological resources present. The geoarcheological investigations, involving the excavation of 10 backhoe trenches and the review of previous data collected within the Upper Trinity River drainage, revealed that the flood plain sediments of the Trinity River are quite variable, both horizontally and vertically. The data collected during the current investigations suggest that Cell D is located along or near the axis of a recent Trinity River meander belt that has cut deeply into the preexisting Quaternary sediments. This channel cut was then rapidly filled with fine-grained deposits possibly derived from the surrounding uplands and other areas upstream. In addition, the trenching revealed that the upper portions of the sediments within Cell D have been disturbed during the recent historic period, presumably by the construction of the Interstate 45 bridge and the activities of the nearby Dallas Central Wastewater Treatment Plant

The Ecology and Evolution of the Freshwater Turtles of Southern Mississippi

Turtles are one of the most threatened group of animals in existence today. The Southeastern United States is one of two global biodiversity hotspots for turtle species, including the state of Mississippi, where over 30 species can be found. However, very few studies have occurred within the state. This lack of research is even more startling given the ongoing decline, or even extirpation, of numerous turtle species across the world, due to a number of factors, including habitat degradation, and harvest for food or the pet trade. The overarching goal of this project was to perform a species inclusive freshwater survey and document the distribution and abundances of the diverse species present here. A substantial amount of data was collected through these surveys, including morphometric measurements, genetic samples, and habitat data recorded at each trap location. These data were then used to determine if riverine habitat and surrounding land cover has any effect on turtle communities. Similarly, a state-wide population genetic study on the Spiny Softshell turtle (Apalone spinifera) was initiated. The surveys performed for this study captured a total of 1,230 turtles, from 16 species. Analyses showed that land-use had no significant impact on turtle communities or species, but that habitat can be a predictor of species occurrence in some circumstances. Finally, our genetic analysis of A. spinifera from the Pascagoula and Pearl River drainages showed two distinct populations between the two drainages, but did not detect any intra-drainage populations structure

Investigation of the Flow and Fate of Nitrate in Epikarst at the Savoy Experimental Watershed, Northwest Arkansas

Many karst aquifers are at high risk of nitrate contamination due to a combination of vulnerable geology characterized by thin soils and conduit flow, and excess inputs of nutrients from animal feeding operations. One zone that is present in many karst regions and could play an important role in nitrate attenuation due to properties such as increased residence time and matrix-water contact is the upper, weathered portion of karst, the epikarst. However, the understanding of this role is lacking, and the objective of this dissertation was to elucidate it. The fate of nitrate in the epikarst was traced along a hydrologic gradient using a multi-faceted geochemical approach based primarily on concentration and stable isotope composition of the reactants and products of denitrification. In addition, dye-tracing tests were conducted to assess the flow, solute transport and aquifer characteristics of the epikarst system. The study found multiple lines of evidence for denitrification which is spatially and temporally highly variable and can remove up to 33% of nitrate along the studied flowpaths. Dissolved organic carbon and dissolved oxygen appear to control denitrification levels, and both in turn appear to be controlled by hydrologic conditions (saturation). However, the most significant agent of nitrate attenuation is dilution, decreasing nitrate concentration by upwards of 50%. Transport of water and solutes in the epikarst can be relatively fast (up to 2.2 m/h) and involves preferential flowpaths. However, transport of a point-source solute located in the upper epikarst depends on saturation, and the transported mass is likely to be negligible in the short term (weeks-months) under the normal weather pattern. Overall, the results indicate that the epikarst can be an important buffer against potential groundwater contaminants

Incorporating digital data into rapid geomorphic assessments

Channel widening and migration can lead to sediment pollution and can be indicative of an imbalanced stream system. Rapid Geomorphic Assessments (RGAs) are on-site methods used to rank stream reaches in terms of stability. RGAs are relatively easy and quick to perform. Subjective measurements and on-site estimates of reach-length parameters create uncertainty in the RGAs. The primary objective of this study was to develop digital RGA methods that integrate readily available data and resources. Digital methods were developed and compared to historical site assessments. Then, the methods were validated by comparing digital RGAs to on-site assessments on several different streams. The digital methods included several different resources, including LIDAR for streambank measurements, Web Soil Survey for bank material and vegetation metrics, and Google Earth to perform visual assessments needed for specific RGAs. Study areas for the validation included second to fourth order streams in Oklahoma in the Ozark Highlands, the Central Great Plains, and the Cross Timbers ecoregions. The resulting digital RGAs performed reasonably well, successfully ranking stream reaches in the same stability ranking as the on-site assessment 38% of the time for two commonly used RGAs: Bank Erosion Hazard Index (BEHI) and the Channel Stability Index (CSI). The digital CSI performed better in the development stage with an 83% success rate. The decrease in performance could be due to several compounding factors such as channel visibility and image availability on Google Earth. Specific metrics should continue to be measured on-site to improve the accuracy of the digital RGAs. For example, a difference of up to twenty points can be avoided if the primary bank material is identified on-site. This project has illustrated the possibility that digital data can be successfully incorporated into RGAs, where digital RGAs have several benefits including the reduced time to assess larger areas and no longer being dependent on land access

Guide to the ecological systems of Colorado

Includes bibliographical references