Name: Total Phosphorus, Total Nitrogen or Chloride Impairments with a 1/4mi Buffer
Display Field: wb_name
Type: Feature Layer
Geometry Type: esriGeometryPolygon
Description: Assessment Units (AU) are the basic unit of record for conducting and reporting water quality assessments to EPA. All assessment units are based on 1:24,000 scale hydrography linked to the National Hydrography Dataset (NHD); the national coverage used by EPA. Surface waters for which data was available to make an assessment, but which were not shown on the base NHD coverage, were added to this coverage on a case-by-case basis and linked to the NHD. Based on the NHD coverage and to facilitate reporting, surface waters were separated into the five waterbody types: rivers and streams; impoundments; lakes and ponds; estuaries; and ocean.AUs are intended to be representative of homogenous segments; consequently, sampling stations within an AU can be assumed to be representative of the segment. In general, the size of AUs should not be so small that they result in an unmanageable number of AUs for reporting. On the other hand, AUs should not be so large that they result in grossly inaccurate assessments.Many factors can influence the homogeneity of a segment. Factors used to establish homogenous AUs include: waterbody type; HUC-12 boundaries; water quality standards; pollutant sources; major changes in land use; stream order; public water supplies; outstanding resource waters; shellfish program categories; designated beaches; and cold water fish spawning areas. Each AU must have a unique identification number (i.e. AUID) to facilitate tracking and reporting of assessment results for each AU. AUIDs are unique to each waterbody and are formatted as SSWWWHHHHHHHHH-UU, where: SS = Stateabbreviation WWW = 3 letters to readily identify the waterbody type RIV = Rivers and StreamsLAK = Lakes and PondsIMP = ImpoundmentsEST = EstuaryOCN = OceanHHHHHHHHH = Last 9 digits of the 12 digit HUC UU = AU segment number Example AUID: NHRIV801060405-01
Service Item Id: b1598d3399a34c1c8dc0ed91c26e3513
Copyright Text: The New Hampshire Department of Environmental Services, Watershed Management Bureau,
Water Quality Planning Section, should be acknowledged as the data source in products derived
from these data.