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- We utilized most HUC levels, from small HUC 12s to larger HUC 6s as shown in our map tab’s layers. However, lower level (larger shapes) seemed of little use within our comparatively small region. Instead, we combined HUC 8 and Mexican subcuencas into major river basins that we thought most biologists interested in aquatic ecosystems would find useful. See our Major River Basin layer in the map tab – this is also our study area.
- We decided to edit the shapes of US HUCs along the Rio Grande that overlapped with Mexico in order to maintain functionality of the website. Allowing overlapping hydrology systems, which we initially preferred, proved to be problematic for a number of reasons. Thus the Rio Grande is uniquely treated and we clipped those US HUCs to meet the Mexican subcuencas, which stop immediately at the Rio Grande. Users should understand that checklists and HUC assignments to occurrences are based on these edited shapes. Furthermore, the Rio Grande, cannot be treated as having hydrologically nested HUCs standard across the US portion of the study area.
- We noticed small areas on the borders of some Mexican subcuencas that we determined were errors and removed them.
- Lastly we changed the names of Mexican subcuencas by removing the "R" prefix they all had in common and replacing it with "MEX".
How are hydrologies used in FoTX:
The current version of the website displays the NHD dataset as a layer on the map tab, but the NHD is not utilized in other ways. Mexican subcuencas and the USGS’ WBD HUC system levels 12 through 6 are used throughout the website, together forming a merged continuous hydrology covering the entire FoTX study area that is used for summarizing and displaying data as described below:
- HUC8s/subcuencas can be viewed on the map tab as independent layers alongside species occurrences.
- Checklists derived from occurrences are available for all HUC8s/subcuencas.
- Native layers for all native species are described as compilations of HUC8s/subcuencas.
- Tableau dashboards summarize the data by HUC8s/subcuencas.
- Native Fish Conservation Areas are compilations of HUC8s/subcuencas.
- All records in the database have been assigned HUC8s/subcuencas based on their coordinates. This is how records are called up in hydrology-based queries from the data tab. Thus, records lacking coordinates, also lack HUC8/subcuencas assignments and are not discoverable using hydrology-based queries. We made HUC8/subcuencas assignments regardless of the size of the occurrence’s spatial error estimate. It is thus conceivable for records with large errors, and especially so for occurrences that are located close to HUC boundaries, to be assigned to HUC8s/subcuencas in which the true occurrence did not occur. Assignment of other categorical assignments (county or NFCA) work the same way.