4 pp. / On Wednesday August 5, 2015, during an EPA mine site investigation of the Gold King Mine near Silverton, CO, heavy equipment caused an unexpected release of acid mine drainage trapped inside a mine tunnel. A sample of the water was analyzed and found to contain several heavy metals such as lead, arsenic, and cadmium. This publication describes the event and evaluates the potential impact to water users below the Lake Powell Reservois and Arizona Farmers.

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Lakes represent a major topographic feature in southern Manitoba, having a direct meteorological influence on a number of communities, including Winnipeg. Therefore, it is crucial that we have an understanding of the characteristics of lake breezes in the region and the influence that they can have on local weather. The Effects of Lake Breezes on Weather in Manitoba (ELBOW-MB) project in 2013 sought to fill in the gaps in our current knowledge of lake breezes in southern Manitoba. The primary research objectives of this thesis are to: (1) provide a radar-based climatology of lake breeze frequency and characteristics and, (2) to characterize the detailed thermodynamic and kinematic properties of lake breezes and lake-breeze fronts. The two results papers presented within this thesis represent the first detailed analysis of lake breezes in southern Manitoba and help to fill important gaps in our knowledge about the occurrence and characteristics of lake-breeze circulations. / February 2016

Twenty-eight species of zooplankton were identified from Lake Texoma. Seasonal density of the overall microcrustacean community and seasonal cycles of individual species were compared with northern populations and any available literature from the Southwest. Cycles of occurrence and abundance were similar to those observed in northern populations but tended to occur earlier in the year due to higher temperatures. Spatial distributions within the reservoir were heavily influenced by nutrient and salt input from the Red River, which resulted in dense populations in the Red River Arm. In addition, during the summer, the microcrustacean community was restricted to the epilimnion due to anoxic conditions in the hypolimnion of the reservoir.

Master of Arts / Geography / Charles W. Martin / Tuttle Creek Dam was built in 1962 after near-record flooding in the Kansas River watershed. It has been in operation for over 50 years. In that time, nearly half of its storage capacity has been filled by sediment, reducing its ability to serve its intended purpose under current operations. The Corps of Engineers authorized a study to examine the sediment in Tuttle Creek Lake and determine management strategies to extend its lifespan. This report examines the erodibility of the sediment as a function of depth and distance to dam. Eight sediment cores were tested and analyzed for two erodibility parameters, critical shear stress and erodibility coefficient. After directly comparing these parameters it was determined that Tuttle Creek Lake sediment ranges from erodible to very erodible regardless of depth or location. Analyzing for locational and depth patterns in erodibility coefficients indicated that both influence the erodibility of sediment, with depth being the stronger factor. These results indicate that locations further upstream from the dam and greater depths are the least erodible. Sedimentation patterns were mapped onto a three dimensional model in ArcMap. It is hoped that this research will assist Corps of Engineers leadership in deciding which management practices to pursue for Tuttle Creek Lake.

Video summarizing Ph.D. dissertation for a non-specialist audience. / Civil and Environmental Engineering / College of Engineering

Lake Rotorua has become increasingly eutrophic over the past 2 to 3 decades. The sediments of the lake have been shown to exert an important influence on this eutrophication process. Chemistry of the sediments has been studied to determine the nature, composition and distribution of elements, through a 1.5 year coring programme. A geophysical survey together with sub-bottom profiling has provided stratigraphic information related to the bathymetry of the lake. Lake Rotorua has two types of sediments: coarse, dense (density c. 0.5 g/cm3) sediments comprised of clastic erosion products and coarse rhyolitic airfall components covering approximately 60% of the lake area; and fine, low-density (approximatly 0.02 g/cm3) diatomaceous ooze that covers the remaining 40% of the lake, accumulated from deposition of biota, predominantly diatom frustules of Aulacoseira granulata. The sediment contains a record of volcanic eruptions, with the Tarawera Tephra typically found 0.5 m below the sediment water interface and Kaharoa Tephra typically between 2 to 3 m depth, in water depths of 10-15 m. Phosphorus concentration in Lake Rotorua sediments decreases with sediment depth. In the centre of the lake phosphorus concentrations in the top 2 cm can exceed 2500 g/tonne and decline to 800 g/tonne at 20 cm depth. Accumulation rate of phosphorus in the sediment based on the nutrient budget is approximatly 29.6 t/yr. Iron and manganese concentrations in the sediment depend on the availability of the element and the sedimentation rate of diatom frustules, and are controlled by the redox conditions in the sediment. The average concentration of iron and manganese in the sediment is approximately 8000 g/tonne and between 300 and 400 g/tonne, respectively. Iron accumulates in the sediment at a rate of 385 t/yr and manganese at 17.9 t/yr. Maximum concentrations of arsenic in the sediment are 250 g/tonne but are generally between 50-100 g/tonne, depending on the water depth. Lead concentrations are typically below 15 g/tonne. Sediment concentrations of both arsenic and lead are highly correlated with iron and manganese concentrations in the sediment and mimic the respective concentration profiles. Arsenic and lead accumulate in the sediment at a rate of 3.71 and 0.49 t/yr, respectively. All elements show a peak in concentration in the tephra layers. The bathymetry of Lake Rotorua is dominated by a curved depression extending from Sulphur Point and almost reaching the Ohau Channel. This depression is probably a structural feature likely associated with the collapse of the caldera, but could be an ancient drainage channel. A series of conical depressions clustered to the north of Sulphur Point and to the east of Mokoia Island are likely to be hydrothermal explosion creators. In the north in the lake at water depths less than 10 m, a series of near-shore terraces are preserved in the sediment. Sub-bottom echo-sounding shows no return of sonic and seismic signals from most of the lake floor, indicating total absorption by the methane gas-filled sediment. In the shallow lake margin environments, generally less than 10 m water depth, gas is absent and a detailed stratigraphy of multiple reflectors from tephra layers was observed with sub-bottom profiles. The basin sediments of Lake Rotorua are significantly pockmarked, with deep, circular flat-bottomed depressions c. 20-60 m diameter and 0.5-6 m depth. The pockmarks are located on the lake floor in areas where the sediment is saturated with gas.