Watershed Monitoring Programs in Fairfax County

Transcription

1 Watershed Monitoring Programs in Fairfax County Innovation and Collaboration in Stormwater and Ecosystem Assessments Department of Public Works and Environmental Services Working for You! A Fairfax County, VA, publication April 27, 2017

2 Presentation Overview: Monitoring in Fairfax Co. Introduction to Fairfax County Need for monitoring programs High-level overview of our diverse programs Brief introduction to our 2 core monitoring efforts: 1. Comprehensive Biological Monitoring Program 2. USGS/Fairfax County stream gage network partnership & trend study Selected results/learnings from study [time permitting] Ancillary study findings [time permitting] 2

3 Welcome to Fairfax County! Chesapeake/Potomac River Watershed 30 watersheds draining ~400 miles 2 1,000 miles of stream (~750 perennial) 3 Physiographic Provinces Suburb of Washington DC Population = 1.14 million Average impervious ~ 25% 2 nd highest median household income in U.S. MS4 Phase I Community FY 18 County budget approx. $4.1billion SWM Program funded through Service District ($0.03/$100 assessed real estate value) $61.8 million for STW Management program 8 Ecologists (in monitoring group) ee3

4 Monitoring Programs the Foundations Basin Master Drainage Plans - mid-1970s: Stream Protection Strategy (SPS) Baseline Study 1999 Comprehsensive Biological Monitoring program instituted Countywide Stream Physical Assessment Watershed Management Plans Streams and Water Quality CIP - $22 M in FY18 Stream Restoration Projects ~ 80% Stormwater Pond Retrofits ~15% Green Infrastructure ~ ~5% VA 305(b)/303(d) listed impaired segments: 2014 Riverine impairments = 386 miles 24 impairments in > 105 impairments in

5 Watershed Monitoring Programs (at a Glance) 1. Comprehensive Biological (>100 sites annually) Probabilistic (stratified random) design - 40 sites/yr. Stream restorations & special projects 10 sites/yr. Reference (trend) - 18 sites USGS gages 20 sites QA/QC 4 sites 2. USGS Gages network trend study 3. Dry Weather Outfall Screening - 100/yr. 4. Wet Weather Outfall Screening 2 sites/yr., quarterly 5. Lakes Study 4 monthly 5

6 Comprehensive Biological Monitoring Stream assessments include: Chemical/physical WQ parameters Physical habitat Bacterial contamination (E. coli) Benthic macroinvertebrates Fish community 6

7 Annual Countywide Stream Assessments Probabilistic design allows statistically valid approach for assessing trends in overall stream health countywide 7

8 How are we doing? Fairfax spending $21 M/year on watershed improvement projects Need to meet Chesapeake Bay TMDL reduction targets: N, P, TSS Need to meet local TMDL reduction targets and biological endpoints. Will WQ improvements = biological improvements? Lag time issues? Attainability? s Billions of $$ will be spent Bay-wide. Individual BMP efficiency/performance ratings > sketchy at best Effect of multiple BMPs at the watershed scale is unknown Are we investing $$$ efficiently & effectively? 8

9 USGS Gages Partnership Trend Study Study Objectives: Phase 1 (Ongoing since 2007) 1. Generate long-term monitoring data to describe: Current water-quality conditions, Trends in water-quality, quantity, nutrient and sediment (loads and yields). Nitrogen (N) Phosphorous (P) Sediment (SSC) Phase 2 (Beginning now) BMP Evaluation 2. Evaluate relationships between observed conditions/trends and watershed BMP implementation. [BMP Evaluation] 3. Transfer the understanding gained to other less-intensively monitored watersheds. [Knowledge Transfer] [Intensive Monitoring] 9

10 BMP induced changes are difficult to quantify at the watershed scale: Environmental factors cause great variability need to separate signal from noise, Lag times may be considerable, Numerous Samples + Continuous Data Multiple Sites Extended Duration 10

11 Objective 1: Intensive Monitoring Operate 5 intensive monitoring stations 10+ years of data collection - Continuous-record stream gage - Continuous water-quality monitor: (turbidity, ph, SC, water temp, DO) - Nutrients & Sediment Sampling - Automated sampler (storm samples) - Scheduled monthly sampling (base flow) - Annual benthic macroinvertebrate monitoring - Develop relationships b/w real-time data and lab samples to calculate - Watershed loads (lbs/year) - Watershed yields (lbs/acre/year) - Real-time estimates of N, P, TSS 11

12 Objective 2: BMP Evaluation Assemble BMP implementation dataset for monitored watersheds. Evaluate relations between water-quality conditions/trends and BMP activities. 12

13 Objective 3: Knowledge Transfer Operate 15 trend monitoring stations (less intensive) Partial-record stream gage Nutrient & sediment sampling Scheduled monthly sampling (wet & dry) Annual benthic macroinvertebrate monitoring Evaluate relations between trendand intensive monitoring sites Cost-effective approach 13

14 Network Site Parameters Continuous Streamgage Continuous Water-Quality Monitor Intensive Sites (5) Stormflow Sampling Monthly Sampling Trend Sites (15) Annual Benthic Macroinvertebrate Sampling Partial-Record Streamgage 14

15 Monitoring Network 5 Continuous Record Gages (intensive) 15 Partial Record Gages (trend) Trend Monitoring Station Intensive Monitoring Station Site Added in WY 2013 All watersheds <5 mi 2 15

16 Site Selection: Land Use Spectrum 16

17 Publications SIR Study purpose and design Summary of 1 st 5 years Water-quality characterizations Surrogate relations Nutrient and sediment loads and yields Comparisons with Chesapeake Bay tributaries and other urban areas Work on next report to begin this year! Trends Assessment of responses to implementation Numerous Ancillary Studies and Pubs USGS Nat l Headquarters in Fairfax County Nitrate (from septic) in surface waters Floodplain processing of nutrients and sediment Sediment fate and transport Fairfax watersheds in context of Ches. Bay SIR

18 Public Access All data, related studies, publications, and reports on web Project Web Page: 18

19 Selected Learnings Sediment movement Nitrate loadings in non-sewered areas Related to density of septic fields P levels in Triassic Basin streams are high Headwaters eroding, but floodplains are sink net sediment budget for Difficult Run Several others Sediment loading is highly episodic- most of the load is generated by a few of the largest storms. Nitrate concentrations at the Difficult Run stream gage have been increasing over the past 35 years 19

20 Monitoring Programs Expensive Time intensive Must be objective-driven Provide critical information for making sound management decisions Current condition characterization Identifies source stressor(s) Insight into trends More efficient use of limited resources Provides learning opportunity Greater rate of success (informs project selections/designs) Monitoring staff work collaboratively with implementation staff Use monitoring data to illustrate success stories 20

21 Additional Information For additional information, please contact Shannon Curtis, Chief, Watershed Assessment Branch