Google Earth Engine

Earth Engine pairs a multi-petabyte catalogue of satellite and environmental data — Landsat, Sentinel, MODIS, precipitation, terrain, land cover, the JRC Global Surface Water record — with cloud compute that runs your JavaScript or Python analysis next to the data. Water applications lead its success stories: global surface-water change, flood mapping, irrigation monitoring, snow and drought tracking.

It is free for noncommercial and research use, with commercial licensing through Google Cloud. The skill transfers everywhere in modern hydrology; start with the JavaScript Code Editor or geemap in Python.