Evaluating the Effectiveness of Agricultural BMPs

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Evaluating the Effectiveness of Agricultural BMPs

• Nancy Mesner
• Utah State University

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CSREES Conservation Effectiveness Assessment for
the Little Bear River
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The Little Bear River a targeted HUA watershed
in the 1990s. Identified pollutants included
phosphorus, sediment and bacterial. Identified
sources included riparian degradation, irrigation
return flows, animal feeding operations

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BMPs included riparian and stream restoration,
offstream watering and fencing, upland
restoration of grazing lands, and manure
management.

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DEQs Ongoing monitoring 2 long term sites,
3-8 other sites sampled every 5 years
Monthly water quality monitoring Biweekly
monitoring - spring runoff

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• Questions that Little Bear CEAP project is
  addressing
• Was there a reduction in phosphorus since 1990?
• If so, can it be attributed to BMPs?
• Are current monitoring techniques adequate?
• How well do alternative wq indicators correlate
  with traditional approaches?
• Are there other factors in the watershed that may
  bias or affect our interpretation of the data?

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• General Questions to Consider When Assessing BMP
  Effectiveness
• What are the goals and objectives of the BMPs?
• When to monitor?
• Where to monitor?
• What needs to be measured?

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Riparian restoration buffers stream, improves
temperature, reduces erosion
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Stream restoration habitat restoration,
improved stream function,
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Grazing / rangeland management sediment,
nutrient, pathogen control
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Irrigation management salinity, sediment,
nutrients
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Manure management nutrient, pathogens
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Effectiveness of BMPs Most studies have
addressed specific BMPs at a test plot or field
scale. Demonstrating watershed changes more
complicated. Appropriate statistical design
difficult Very few studies linking BMPs to
changes in beneficial uses (fisheries)
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Considerations BMPs work in field studies but
need to consider NP ratios in manure vs plant
requirements leads to build up of P if using N
requirements Trade offs between N contamination
(groundwater) and P contamination (surface water)
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• Findings
• Successful BMPs require greater amount of
  oversight and management than previously thought.
• Limit application rate to agronomic rates
  (requires manure and soil testing)
• Use in coordination with buffer strips, etc.
• Consideration of time of year of application
  (requires storage)
• May need to expand application area
  (increased costs)
• Composting and soil amendments (unknown
  consequences)

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• When to monitor?
• Typical water qualty monitoring plan involves
  regularly spaced sampling (eg. quarterly or
  once/month)
• ? Long term dataset

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Typical monitoring program measures water quality
at a relatively few points in time, then
connects the dots. Note Total annual load
is assumed to be the area under the curve.
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However If storm events arent measured, the
actual load may be much larger.
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• Many monitoring schemes miss daily variation as
  well.
• Blue dots are typical late afternoon
  measurements of dissolved oxygen. In many
  productive systems, however, DO drops to very low
  values at night.

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All Samples
Comparison of storm event data with non-storm
data at 8 different urban stations in Utah
Note difference in percent exceedence of
pollutant criteria. Data from Rieke, Mesner
and Gilles, 2005
All Samples
Non Runoff Samples
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• Consider temporal effects
• Temperature only an issues in summer
• Dissolved Oxygen may only be an issue in summer
  or late winter.
• Ag return flows only an issue during irrigation
  season.
• Target timing of monitoring to best evaluate the
  BMP.
• IF your bmp is effective during runoff periods,
• then monitor during runoff windows.

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• Where to monitor?
• Upstream / downstream
• At bottom of watershed
• Multiple sites
• Do you know the critical contributing areas in
  the watershed?
• Consider size of total watershed vs size of bmp

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• Are you monitoring in the right locations?

Problem excess sediment BMP series of small
in-stream sediment basins Average flow 20 cfs
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• Upstream/downstream monitoring demonstrates
  impact of BMP very effectively.

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• But will upstream/downstream monitoring capture
  all impacts?

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• Loading from large feeding operation swamped by
  the large loads carried by the Bear River.

upstream
downstream
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Upstream / Downstream IF.. You are measuring
direct instream effects OR during a storm/runoff
event AND the magnitude of the reduction is
large compared to the total load in the stream
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Measuring bmp effectiveness at a watershed scale

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• One example of a watershed scale study that
  looked at effectiveness of BMPs on fisheries.
• Wang et al (2001) - Used BACI (before after
  control impact) design to evaluate effects on
  habitat and fish populations in 2 watersheds
• Paired reference streams (increased power)
• 2 regional least impacted streams (upper end
  conditions)
• Modified fish sampling

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NPS issues livestock, grazing, feedlots
NPS issues excessive pasturing along stream
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Findings BMP implementations improved overall
stream physical habitat conditions. However
Spring Creek (with relatively large amounts of
BMPs in both upland and riparian) ? improved
habitat, temps and fisheries Joos-Eagle (with
very few BMPs installed) ? No change in fish or
thermal regime ? habitat only improved in
localized areas.
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• Findings
• Fisheries improvement thru riparian bmps alone
  will only work if the watershed is already in
  good shape, or if upland bmps are installed.
• A minimum of 30-50 bmp implementation at a
  watershed scale may be necessary

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Challenges for evaluation of watershed-scale
BMPS Often difficult to get enough BMPs
installed This makes experimental design
difficult BMPs require gt 5 years to be effective
at system level, which may be outside of
monitoring plan scope. Limitations in
monitoring strategies may miss actual
changes Poor controls for other factors (changes
in land use, drought, etc).
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• What to monitor?
• Measure everything?
• Measure pollutant of concern?
• Measure surrogates?
• Measure actual beneficial use?
• Consider goals of monitoring and goal of specific
  implementation.

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• For example,
• Manure application to fields as a means of
  managing excess phosphorus
• Can lead to nitrogen leaching / groundwater
  problems.
• Targeted monitorng of phosphorus in surface water
  could entirely miss nitrogen problem in gw.

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Which parameters to monitor?

• Chemical Data (TDS, Nutrients, TSS, metals)
• Biological Data
• Macroinvertebrates
• Sensitive (Indicator) species, Functional Groups
• Riparian (Green Line)
• HQI
• Stream Geomorphology

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Example from grazing management project on BLM
land in western Wyoming. Chicken Creek
1989
Photopoints can be are very effective at
demonstrating impact.
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Proper Functioning Condition Stream Re-assessment
2000
1989
PFC measurements provide indicators of system
response.
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Chicken Cr. Greenline Study Site T.19N., R.118W.
Sec. 5
Green line monitoring provided more quantitative
data. Note the quantitative objectives of
project on graph.
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Utahs interagency monitoring team visits
selected sites every few years. Target a few
reference and implementation sites.
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(No Transcript)
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Transect Locations at Curtis Property
G2
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Surveying demonstrates response of stream width,
depth, lateral migration. In these cross
sections, stream has deepened and narrowed at BMP
site.
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Macroinvertebrate indices integrate over time.
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Woody plan transects measure response of riparian
area to BMPS.
Age Class Trend in Total number of Woody Plants
1994 1995 1996 1998
Seedling 156 364 300
324 Young 74 148 165 208 Mature
15 28 45 49 Decadent 2
2 0 0 Dead 0
0 0 0
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Habitat Quality Index measures quality of fish
habitat.
1999 2003 Flow Velocity
3 0.5 Average width 25.2
18.9 Feet of eroded Bank 22
0 Macroinvertebrates High Quality High
Quality Macroinvert. Nos Adequate Adequate I
nstream Cover (ft2) 1633 4343
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The reports also utilize monitoring data
collected by DWQ. In this example, response was
measured as a change in the slope of the
TP/discharge relationship.
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• In evaluating effectiveness of BMPS, it is
  critical to look for other changes in the
  watershed that become the driving factors?
• Land use changes?
• Climatic patterns?
• Changes in ownership?

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BMPs installed to protect banks from direct
impacts of animal grazing.
Several years later, ownership of land had
changed and BMPs were no longer in place.

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Urbanization
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In conclusion Keep project goals in mind when
monitoring BMPs Monitor at an appropriate
scale Keep time lags in mind Be selective,
consider individual situations Monitor surrogates
when appropriate Control or measure human
behaviors / other watershed changes.