TMDL Development Priority HUC Basins

A TMDL (Total Maximum Daily Load is a scientific determination of the maximum amount of a given pollutant that a surface water can absorb and still meet the water quality standards that protect its designated uses including recreation, human health, and aquatic life. Water bodies that do not meet water quality standards are identified as 'impaired' for the particular pollutants of concern — nutrients, bacteria, mercury, etc. — and TMDLs must be developed, adopted and implemented for those pollutants to reduce pollutants and restore the water body so that designated uses are attained. The threshold limits on pollutants in surface waters — Florida's surface water quality standards on which TMDLs are based —are set forth primarily in rules 62-302 and 62-303, Florida Administrative Code (FAC), and the associated table of water quality criteria. Adopted TMDL rules are included in Chapter 62-304, FAC. The data layer depicts the hydrologic basins where the State of Florida has proposed future development of TMDLs through 2022. These basins are based on the Hydrologic Unit Code (HUC) watersheds that are delineated by USGS using a nationwide system based on surface hydrologic features. This system divides the country into 21 regions (2-digit), 222 subregions (4-digit), 370 basins (6-digit), 2,270 subbasins (8-digit), approximately 20,000 watersheds (10-digit), and approximately 100,000 subwatersheds (12-digit). The HUC basins shown here are at the 8-digit level.总最大日负荷量（Total Maximum Daily Load，TMDL）是一项科学测定方法，用于确定某地表水体可吸纳的特定污染物最大限值，且仍能满足保护其指定用途的水质标准，这些指定用途包括休闲娱乐、人体健康保护以及水生生物养护。未达到水质标准的水体，会被认定为针对所关注的特定污染物（如营养物、细菌、汞等）的「受损水体」，需针对此类污染物制定、采纳并实施TMDL，以削减污染物排放量、修复水体，使其恢复既定使用功能。 TMDL所依据的佛罗里达州地表水质污染物阈值限值，主要规定于《佛罗里达行政法典》（Florida Administrative Code，FAC）第62-302条与第62-303条，以及配套的水质标准表。已正式采纳的TMDL规则收录于FAC第62-304章。 本数据图层展示的是截至2022年，佛罗里达州计划未来开展TMDL开发工作的水文盆地。此类盆地基于美国地质调查局（USGS）依托全国地表水文特征体系划定的水文单元代码（Hydrologic Unit Code，HUC）流域。该体系将美国划分为21个一级区域（2位代码）、222个次级区域（4位代码）、370个流域盆地（6位代码）、2270个子流域（8位代码）、约20000个10位代码流域，以及约100000个12位代码子流域。本次展示的HUC盆地为8位代码级别。