dog river watershed management plan preliminary data analysis · total 63,877 112,180 305,384...
TRANSCRIPT
Dog River and Garrows Bend
Watershed Management Plan
Ambient Water Quality and
Pollutant Loading Estimates
Doug Robison, PWS
Management Measures Working Group
July 26, 2016
Stakeholder Water Quality Concerns
• Trash
• Sediment
• Sewer overflows
• Algae blooms
• Safe fishing & swimming
Water Quality Data Sources
• Alabama Department of Environmental Management
(routine ambient monitoring)
• Alabama Water Watch – Dog River Clearwater Revival
(volunteer monitoring)
• Mobile Area Water & Sewer System (special study)
• Geological Survey of Alabama (special study)
• Mobile Bay National Estuary Program (baseline survey)
• Dog River is a tidal river
estuary
• Sub-basins and major
tributaries
– Upper Dog River
• Eslava Creek
• Bolton Branch
– Halls Mill Creek
– Lower Dog River
• Rabbit Creek
• Garrows Bend sub-
basin flows directly to
Mobile Bay
Water Quality Parameters of Concern
• Dissolved oxygen
– Measure of organic enrichment
– Critical for healthy fish & shellfish
populations
• Chlorophyll-a
– Measure of algal production and
organic enrichment
– Driven by excessive nitrogen and/or
phosphorus
• Bacteria
– Measure of animal waste discharges
– Indicator of human pathogens
• Heavy metals
– More problematic in urban watersheds
– Toxic accumulation in sediments & food
chain
Upper Dog River
Halls Mill Creek
Lower Dog River
Garrows Bend
Water Quality Summary
Upper Dog
River
Halls Mill
Creek
Lower Dog
River
Garrow’s
Bend
Dis. Oxygen
Chlorophyll-a
Nutrients
Bacteria
Metals
Good Fair Poor No Data
Dog River Watershed - Impaired Water
Bodies
Tributary/Segment Impairments
Halls Mill Creek Siltation (303(d) list)
Bolton Branch Pathogens (approved TMDL)
Eslava Creek Pathogens (approved TMDL)
Rabbit Creek Organic Enrichment (approved TMDL)
Pathogens (approved TMDL)
Dog River Organic Enrichment (approved TMDL)
Pathogens (approved TMDL)
NPS Pollutant Loading Model
• GIS-based model
• Links key watershed parameters
– Topography
– Land use
– Soil types
• Applies actual rainfall data
• Calculates annual runoff pollutant loads
– Nutrients, sediment, and heavy metals
– Based on actual event mean concentration (EMC) data
measured in the southeastern U.S.
Watershed Topography
Watershed Land Use
Watershed Soils
Pollutant Loadings by Sub-Basin
• Greatest pollutant loads are from the Upper Dog River– Greatest hydrologic load
• Differential pollutant loads per unit area among sub-watersheds– Differences in land use and soils
Estimated Load (Pounds/Year)
WatershedArea
(Acres)
Runoff
Volume
(Ac-Ft)
TN TP BOD TSS Copper Lead Zinc
Garrow's
Bend4,221 8,372 31,511 4,609 106,845 571,822 171 51 779
Halls Mill
Creek20,863 28,486 76,622 11,352 242,496 1,272,934 406 114 1,729
Lower Dog
River16,996 35,842 58,759 8,771 188,409 1,007,041 310 91 1,366
Upper Dog
River21,798 39,480 138,492 20,394 472,764 2,517,176 751 224 3,399
Total 63,877 112,180 305,384 45,126 1,010,515 5,368,973 1,637 480 7,273
Highest Pollutant Loading Areas
Water Quality Recommendations
• Greatest needs are in the Upper Dog River
• Improve public education to reduce illicit
discharges and encourage urban BMPs
• Continue to identify and mitigate failing
wastewater infrastructure
– Severe Weather Attenuation Basins (SWABs)
• Identify potential stormwater treatment sites
– Floatable trash skimmers
– Attenuation/sedimentation basins
– Wetland treatment systems
Potential Treatment Areas
Offline Wetland Treatment System
Salt Barrier
Estuary
Low FlowDiversionStructure
Questions