Hyperspectral Imaging from a Multipurpose Floating Platform to Estimate Chlorophyll-a Concentrations in Irrigation Pond Water

This study provides detailed information about the use of a hyperspectral imaging system mounted on a motor-driven multipurpose floating platform (MFP) for water quality sensing and water sampling, including the spatial and spectral calibration for the camera, image acquisition and correction procedures. To evaluate chlorophyll-a concentrations in an irrigation pond, visible/near-infrared hyperspectral images of the water were acquired as the MFP traveled to ten water sampling locations along the length of the pond, and dimensionality reduction with correlation analysis was performed to relate the image data to the measured chlorophyll-a data. About 80,000 sample images were acquired by the line-scan method. Image processing was used to remove sun-glint areas present in the raw hyperspectral images before further analysis was conducted by principal component analysis (PCA) to extract three key wavelengths (662 nm, 702 nm, and 752 nm) for detecting chlorophyll-a in irrigation water. Spectral intensities at the key wavelengths were used as inputs to two near-infrared (NIR)-red models. The determination coefficients (R2) of the two models were found to be about 0.83 and 0.81. The results show that hyperspectral imagery from low heights can provide valuable information about water quality in a fresh water source.

Population Dynamics and Seasonal Occurrence of Adult Amphipsyche meridiana Ulmer 1902 (Trichoptera: Hydropsychidae) in an Irrigation Pond Outlet

Population dynamics and seasonal occurrence of adult Amphipsyche meridiana Ulmer, 1902 (Trichoptera: Hydropsychidae) in an irrigation pond outlet at Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom Province were determined, with the influence of air temperature, wind speed, precipitation and relative humidity on its population density being evaluated. Samples were collected monthly from January to December 2013 by light trapping. Monthly sampling records for adults collected were 24876, 2605, 29344, 43632, 18684, 16524, 29871, 15183, 10548, 17100, 7695 and 15678, respectively. An increase in the number of adults collected was observed from January to July with peaks of 43,632 (18.83%) in April. A remarkable decrease in the number of insects collected was observed in the months after August. There was an increase in the number of adults most influenced by the decrease in precipitation and relative humidity.