This repository provides the `lidar` Python package, a specialized library for hydrological depression analysis of high-resolution topographic data, particularly LiDAR-derived DEMs. Its core functionality includes DEM smoothing (mean, median, Gaussian filters), sink extraction, and a novel level-set algorithm for delineating nested depression hierarchy, yielding topological and geometric properties (size, volume, depth, perimeter). The package is designed as a reusable library with a CLI (`lidar` command), a PySimpleGUI-based graphical interface, and integration with ArcGIS via a dedicated toolbox. It also includes Jupyter notebooks for tutorial and research workflows, demonstrating the complete analysis pipeline. The project is research-grade, backed by peer-reviewed publications, and follows a modular architecture with separate modules for filtering, filling, slicing, and mounts. However, some dependencies (GDAL, arcpy) and Python version constraints introduce moderate technical drift risk.