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Center for Earth and Environmental
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2007
Research Program Empirical and Bio-optical Modeling of Hyperspectral Reflectance for Improved Mapping of Water Quality Parameters in Central Indiana Reservoirs Nuisance blooms of blue-green algae are seasonally prevalent in Indianapolis’ three reservoirs: Geist, Morse, and Eagle Creek. These blooms can lead to aesthetic degradation of drinking water resources (e.g., surface scums on the water and taste and odor in drinking water). Some blue-green algae are able to produce toxins which can lead to adverse human health effects. Current methods for detecting blue-green algae are both costly and time consuming, which can lead to delayed management decisions. However, remote sensing techniques that utilize the optical properties of blue-green algal pigments (chlorophyll a and phycocyanin) can meet the need for rapid detection and assessment of blue-green algal distribution. Several previously developed algorithms were applied to boat-collected field reflectance spectra to predict the phytoplankton pigment concentrations in the reservoirs. Preliminary results show that the algorithms are able to predict up to 90% of the variability in phycocyanin concentration and thus blue-green algae distribution. While the algorithms are robust, data will be analyzed to further optimize their applicability to Indianapolis’ water reservoirs, thus, providing water quality managers with a survey tool for the rapid delineation and quantification of nuisance blue-green algae.Contaminant Transport Dynamics During Storms in Medium to Large River Systems of the Midwest The study determined variations in nitrate, phosphorus, and dissolved organic carbon concentration in two small catchments in Eagle Creek watershed during spring and summer storm events and identifying the specific ways these nutrients are moved from the land into streams. Two independent techniques were used to determine the specific flow paths and include use of oxygen isotopes and major cations as change in their concentrations throughout a storm event indicate whether the water is sourced from precipitation, shallow groundwater, or surface runoff. Identifying changes in water sources during events using these two independent approaches allows for a better characterization of nutrient export processes in the two watersheds. This work will aid in understanding of both where and when nutrients are being exported into streams in both agricultural and developing areas of the Midwest that can guide nutrient management decisions to improve water quality. Internal Phosphorus Cycling in an Urban Drinking Water Reservoir Sediments can provide a detailed history of the evolution of a reservoir, much as tree rings can provide a history of the growth and climatic conditions in a forest. For sediments, this history is extracted by taking core samples through the sediments that have accumulated at the bottom of the reservoir. These cores record the annual layers of sediment that accumulate in the reservoir, providing information about input from rivers, as well as the active biological processes that occur within the reservoir itself. Of interest was the geochemical history recorded from sediment cores in Eagle Creek Reservoir, which would provide information about how patterns have changed since the formation of the reservoir. In particular, we were interested in understanding the role that sediments from the bottom of the reservoir play in nutrient cycles in the reservoir waters. Under conditions of stagnant circulation and warm surface water common late in the summer, nutrients are released into the overlying reservoir water. These excess nutrients may provide nuisance algae with enough nutrients to bloom, degrading water quality and causing taste and odor in drinking water.
We took several complete sediment cores from the
bottom of Eagle Creek Reservoir, selecting sites that spanned a
range of bottom conditions. We were able to identify the
pre-flooding surface within our ~1 meter long cores, and observed
that ~65 cm of sediment has accumulated in the bottom of the
reservoir since flooding in 1967, amounting to a sediment
accumulation rate of about 1.8 cm/yr. The reservoir sediment was
typically soft and green-gray colored, being comprised of very fine
silt-sized particles and relatively enriched in organic matter
(6-14%). Layering was easily observed in the sediment core, likely
reflecting seasonal changes in watershed runoff and biological
activity. The nutrient content of the sediments is very high. For example, the concentration of the biologically limiting nutrient phosphorus is about 1.8 mg/g, putting it in range with other Midwestern reservoirs which also have high biological productivity. One of our key findings was that the percentage of the phosphorus that is highly sensitive to low oxygen conditions was very high (typically about 70% of the total phosphorus content). Because of seasonal patterns in stratification of the reservoir waters themselves, the bottom waters of the reservoir become oxygen-depleted. These low-oxygen reservoir conditions result in the oxygen-sensitive phosphorus in the sediments becoming mobilized and “leaking” back to the reservoir waters. The excess phosphorus becomes available to feed algal blooms and degrades water quality. Thus, the reservoir sediments themselves play a role in the formation of algal blooms. This understanding helps resource managers understand that algal bloom management in Eagle Creek Reservoir will require both watershed management to reduce nutrient inputs from stream flow as well as strategies that manage low-oxygen bottom water conditions.
Effects of Land Cover on Water Quality and Nutrient Loading Research focused on understanding the influence of land cover on the amount and timing of water and nutrient delivery to streams in Eagle Creek Watershed. Research was completed in Fishback Creek and School Branch Creek on the northwest side of Indianapolis. Both watersheds are rapidly developing from agricultural to residential land use and flow directly into Eagle Creek Reservoir, a source of drinking water for the City of Indianapolis. Increased nutrient input from the watersheds is believed to be a cause of increased algal blooms observed in the reservoir. The study utilized a holistic approach to watershed research and management, combining in-stream water sampling, continuous monitoring, and remote sensing technologies. Results of the study indicated that the influences of different land cover types on water delivery to streams and in-stream water quality vary seasonally and with respect to flow conditions. Additionally, study results suggested that a land cover change from agriculture to development will affect the concentration and loading of some water quality parameters (nitrogen) while others will likely remain the same (phosphate).
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