Abstract

This study shows the results of testing previous research that used remote sensing techniques to determine chlorophyll-a concentrations in turbid surface waters, and developing similar methods and models for Utah Lake using Landsat 7 ETM+ satellite imagery and field measured concentrations of chlorophyll-a. The data for the study included images acquired on June 22 and July 8, 2009. The field data included ground measurements taken on June 22 and July 6, 2009 from seven water quality sampling locations. The 48 hour time difference between the Landsat image acquisition (July 8) and the field measurement (July 6), and the small sample size for the data analysis were potential sources of error. The log transformation of red/near-infrared reflectance (i.e. ln[Band3/Band4]) had a high correlation with the field measured chlorophyll-a concentrations (R^2 = 0.9337). With this relationship, a model and 19 contour maps showing the spatial distribution of chlorophyll-a concentrations over Utah Lake was developed for the spring, summer, and fall seasons of 2003 to 2010. Generally about 90% of the Lake area had chlorophyll-a concentrations lower than 20µg/L. High concentrations of Chlorophyll-a (355µg/L and over) were observed mostly at the Provo Bay and Goshen Bay areas of the Lake. Occasionally, elevated levels of chlorophyll-a were observed at the northeastern, middle, and western sections of the lake. Utah Lake's average chlorophyll-a concentration is declining over time. In spring, the Lake average chlorophyll-a concentration reduced from 30.51µg/L in 2004 to 7.08µg/L in 2010. In summer, this average reduced from 132.13µg/L in 2003 to 36.58µg/L in 2010. Finally, in fall, the Lake average chlorophyll-a concentration reduced from 273.40µg/L in 2006 to 33.59µg/L in 2010. Field measured concentrations of phosphorus and model estimates for chlorophyll-a concentrations were highly correlated (R^2 = 0.9046). This suggests that the elevated levels of chlorophyll-a might be a result of the point and non-point discharge of phosphorus-laden wastewater from treatment plants, municipal storm drains, and agricultural activities.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering

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