Water Quality Resource Inventory
The Nature Conservancy (TNC) partnered with The Natural Resources Conservation Service (NRCS) to develop a water quality hot spot tool to aid in targeting 12 digit sub-watersheds within 8 digit sub-basins in Louisiana for targeted nutrient reduction conservation practices (e.g., winter cover crops, hydrological restoration, reforestation, etc.). The functional requirements of the application were scoped in a series of joint meetings between Louisiana-based TNC and NRCS staff. As a result of these meetings, three 8 digit sub-basins were chosen to pilot the project: Boeuf, Tangipahoa and Mermentau. In the end, the entire state was encompassed in the assessment. The following water quality traits were also selected for analysis: dissolved oxygen, turbidity, total dissolved solids, total suspended solids, total nitrogen, nitrate, total phosphorus, phosphate, ammonia and inorganic nitrogen.
The tool features three workflows that allow you to explore spatial concentrations, temporal trends or impaired watersheds in Louisiana. Supplemental data such as land cover and soils data are also included to aid in visualizing water quality resources and provide landscape context.
The spatial concentration or “hot spot” analysis was accomplished using readily available existing sample data from the EPA and the Louisiana Department of Environmental Quality (LDEQ). These sample data were interpolated within 8 digit sub-basins (HUC 8) to create heat maps. This allows users to evaluate 12 digit sub-watersheds based on relative concentrations of water quality traits within each HUC 8 along with the supplemental data. The temporal trends display all of the sampling stations and allows you to click on a station to view yearly mean values and monthly values within each year of available data for the selected traits.
Third, you can view impaired watersheds, which are visual representations of LDEQ’s 303(d) Impaired watersheds list. This workflow displays a map of all of the LDEQ sub-segments in Louisiana symbolized by TMDL priority. Sub-segments in green have no listed impairment while listed sub-segments are colored yellow for “low priority”, orange for “medium priority” and red for “high priority”. You can also click on the sub-segment to view the grid of impairments, causes and sources.
In addition to the original three pilot watersheds, The Nature Conservancy elected to expand the application to include all 57 HUC 8 watersheds in Louisiana. The spatial analysis has been extended to all watersheds except those where it is not possible to interpolate because there either were not enough sample points or where the shape of the watershed is too narrow and sinuous to create a heat map. The temporal analysis has also been extended to all watersheds along with all available supporting data.
Explore the tool on our Louisiana Freshwater Assessment site or use the Launch Mapping Portal button on this page and click Louisiana.
Photo credits this page ~ Main image: Doug Blodgett/TNC