Functional forecasting of dissolved oxygen in high‐frequency vertical lake profiles

Abstract

Predicting dissolved oxygen (DO) in lakes is important for assessing environmental conditions as well as reducing water treatment costs. High levels of DO often precede toxic algal blooms, and low DO causes carcinogenic metals to precipitate during water treatment. Typically, DO is predicted from limited data sets using hydrodynamic modeling or data-driven approaches like neural networks. However, functional data analysis (FDA) is also an appropriate modeling paradigm for measurements of DO taken vertically through the water column.In this analysis, we build FDA models for a set of profiles measured every 2 hours and forecast the entire DO percent saturation profile from 2 to 24 hours ahead. Functional smoothing and functional principal component analysis are applied first, followed by a vector autoregressive model to forecast the empirical functional principal component (FPC) scores. Rolling training windows adapt to seasonality, and multiple combinations of window sizes, model variables, and parameter specifications are compared using both functional and direct root mean squared error metrics. The FPC method outperforms a suite of comparison models, and including functional pH, temperature, and conductivity variables improves the longer forecasts. Finally, the FDA approach is useful for identifying unusual observations.

Sub-Liquid and Atmospheric Measurement Instrument To Autonomously Monitor the Biochemistry of Natural Aquatic Ecosystems

“…Temperature, pH, dissolved oxygen, total suspended solids, ammonia, nitrite, and nitrate concentrations have to be continuously measured to evaluate the permissible levels for aquaponic systems that provide information about the survival, growth, and food intake of fish. , Also, pH is an excellent indicator to observe the nutritional profile in freshwater fishery sectors, including calcium, magnesium, iron, manganese, and zinc, and monitoring the electrical conductivity, pH, and oxidation–reduction potential becomes vital in brackish water fish cultures . The same parameters can also be used to assess the quality of groundwater that could be compromised by anthropogenic activities, industrial effluents, , and algal bloom contamination. , …”

“…42 The same parameters can also be used to assess the quality of groundwater that could be compromised by anthropogenic activities, 43 industrial effluents, 44,45 and algal bloom contamination. 46,47 Although the SAM instrument offers several research and industrial applications, the deployment and operation of the SAM instrument do come with risks and challenges. Some of the field sites, including saline lakes, may host salt crusty deposits on lake surface, making the floating platform's maneuvering tricky.…”

“… 42 The same parameters can also be used to assess the quality of groundwater that could be compromised by anthropogenic activities, 43 industrial effluents, 44 , 45 and algal bloom contamination. 46 , 47 …”