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Many features of the website utilize the Hydrologic Unit Code (HUC) System (Watershed Boundary Dataset, WBD) developed by the United States Geological Survey (USGS) with some minor variations explained below. We also display the USGS National Hydrography Dataset (NHD), which depicts lentic and lotic waters of the state. To learn about these datasets visit the USGS website here.
Unfortunately, the USGS has only drawn HUC areas for not created HUCs throughout the study area, into Mexico. U.S. HUCs cover a small part of Mexico that extend extending from U.S. HUC’s across the border a short distance into Mexico. This is no surprise since the system was primarily developed for the United States, but in order to expand our study area into Mexico (major addition for Version 3 of the website and database) we had to implement a similar system that could work in concert with the U.S. HUC system. Mexico’s National Institute of Statistics and Geography (INEGI) created a similar, albeit completely independent, system with three levels of nested hydrologic connected areas. We used their lowest ‘subcuenca’ level, which we though sufficiently similar to USGS HUC 8s to provide a complete hydrological watershed boundary dataset for the study area.
Edits to United States HUC and Mexican subcuenca systems:
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