Estuaries are wetlands where freshwater from streams mixes with salt water from sea. Also known as “kidneys of our planet”- they are extremely productive environments that filter pollutants, absorb floods from sea level rise,and shelter a unique ecosystem. However, eutrophication and loss of native species are ailing our wetlands. There is a lack of uniform data collection and sparse research on correlations between satellite data and in situ measurements (measurements made on the ground level). But a tool called remote sensing (RS) may be showing some promise in bridging this gap.
This project attempts to use satellite data and correlate metrics with in situ observations, collected at five U.S. west coast estuaries. The 5 west coast estuaries under study were: San Francisco Estuary, Elkhorn Slough, Tijuana Bay, South Slough, and Padilla Bay. Images for satellite data were processed to calculate 7 bands (SIs or satellite indices) using Python. Average SI values were calculated per month for 23 years. Publicly available data from estuaries was used to obtain 10 parameters (OPs). Average OP values were calculated per month for 23 years. Linear correlations between the 7 SIs and 10 OPs were made and found to be inadequate (correlation = 0 to 44%). Fourier transform analysis on 7 SIs was performed. Dominant frequencies and amplitudes were extracted for 7 SIs and four machine learning(ML) model algorithms were trained, validated, and tested for 10 OPs. The OPs saw improved R2 values in the range of 96.1% to 99%.
This novel approach can be used to get periodic analysis of overall wetland health with satellite indices. It proves that remote sensing can be used to develop correlations with critical parameters that measure eutrophication in situ data and can be used by practitioners to easily monitor wetland health.