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Center for Earth and Environmental
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2006
Research Program Quantifying Blue-Green Algae of Central Indiana Reservoirs Using Hyperspectral Reflectance Through funding provided by the Indiana Department of Natural Resources LARE Grant and Veolia Water Indianapolis LLC., the study focused on the development of a more efficient survey tool to determine blue-green algae concentration and spatial distribution in drinking water reservoirs. The approach of the research utilizes the spectral characteristics, i.e. the changes in how light from the sun is absorbed, of chlorophyll a and phycocyanin, as captured by the Airborne Imaging Spectrometer for Applications (AISA) airplane-based sensor. Chlorophyll a and phycocyanin are light absorbing pigments that are used by blue-green algae photosynthesis, thus changes in light absorption and reflection indicates the presence of blue-green algae. The image data from one of the three reservoirs in the study, Geist Reservoir, has been processed. Results from this Reservoir have yielded two successful algorithms for the prediction of chlorophyll a and phycocyanin. The algorithms can then be applied to the data collected to generate high spatial resolution (1 m2) maps of chlorophyll a and phycocyanin distribution in Geist Reservoir. Additional work is also mapping Morse and Eagle Creek Reservoirs. Development of Time-Series Models for Water Quality Management in Eagle Creek Reservoir Eagle Creek Reservoir supplies approximately 15 million gallons per day (MGD) of drinking water to the T. W. Moses water treatment plant. For many years, Indianapolis Water has heard complaints about taste and odor issues related to water from ECR. In recent years, blue-green algae that are capable of producing toxins that may remain in the water column, have been identified, and it has become clear that strategies must be devised for anticipating major algal blooms and mitigating their effects on drinking water quality. To that end, the Central Indiana Water Resources Partnership (CIWRP), has developed a network of 13 monitoring stations within the ECR watershed, including two within the lake, that collect continuous water quality, weather, and lake data. It is expected that these data will allow scientists to characterize the processes taking place within the reservoir and to devise strategies for long–term water quality management. Although the proximate causes of algal blooms in ECR are not fully understood, in many cases they can be correlated to recent mixing events. ECR exhibits numerous mixing events during the course of the year. Mixing events can release nutrients in the bottom waters into the water column, increasing the possibility of algal blooms. The current monitoring network makes it possible for the scientists at CEES to identify the timing of algal blooms and mixing events, and at least in some cases, to identify the proximate cause of mixing events, e.g. wind stress or inflows from streams. The objective of this project is to find ways to use data from the monitoring network to identify the characteristics of time periods just prior to particular events of interest (e.g. algal blooms or mixing events), and to devise a strategy for identifying the onset of “pre–event” conditions prior to an algal bloom. This forecasting will be achieved by the application of statistical time–series analyses. Information from the models then can be applied as part of a reservoir water quality management plan. Stream Nitrate and Organic Carbon Dynamics during Storms in Eagle Creek Watershed This study investigated nitrate and dissolved organic carbon (DOC) export during three spring storm events in an agricultural watershed and a mixed agricultural/urban land use watershed in a till landscape in Central Indiana (Schoolbranch and Eagle Creek). The objectives of the study are (1) to determine how land use affects water, nitrate, and DOC delivery (timing, amount) to streams during spring storms, and (2) to determine nitrate and DOC flow pathways to streams during storms. High frequency stream sampling of nutrients and cations, coupled with hydrograph separations using δ18O, were used to identify water flow pathways and event and pre-event water contributions to the streams. Results indicate that nitrate and DOC concentrations display distinct temporal patterns during spring storm events. DOC concentration increased with stormflow, and peaked with discharge and the peak in event water regardless of land use or storm characteristics. Nitrate concentrations followed Ca2+, Mg2+, and Na+ trajectories and decreased with stormflow in both watersheds. In addition, the nitrate concentration peak was delayed relative to DOC in the mixed land use watershed. Data suggest that during storms, DOC is exported either via overland flow or via preferential flow through soil macropores. On the other hand, nitrate appears to be mainly delivered to streams in association with pre-event water via subsurface flow. This study contributes to a better understanding of nutrient export pathways during storms for a variety of land uses and to the development of better management strategies and nutrient loading models at the watershed scale. It has aided our understanding of both where and when nutrients are being exported into streams in both agricultural and developing areas of the local watersheds and helping guide nutrient management decisions to improve water quality. |
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Center for Earth and Environmental
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