This visualization shows water level trends over time for two monitoring wells (OW2DWL and OW2DSWL) in a line chart with a color legend and a linked brushing chart below. The main chart displays a dashed grey trendline calculated via least squares regression, with an equation label, while the brush chart filters the data range and recomputes the trendline interactively. Built using D3 v5, it applies `scaleTime`, `scaleLinear`, `scaleOrdinal`, `line`, `brushX`, and `axisBottom`/`axisLeft` to render SVG paths and axes. Data is loaded from a CSV file via `csv`, with date parsing through `timeParse` and event-driven brushing updating the trendline and equation.