70th SWCS International Annual Conference July 26-29, 2015 Greensboro, NC

1. A framework for setting realistic expectations
for water quality improvements based on
changes in agricultural activities
Paul Capel and David Wolock
U.S. Geological Survey
Soil and Water Conservation Society Conference
Greensboro, NC
July 27-28, 2015

2. Chemicals and sediment from fields enter the stream network
Annual loads transported
to the Gulf of Mexico
Nitrogen:
1000 – 2000 metric tons/year ~$1B
Phosphorus:
150 – 250 metric tons/year
Sediment:
600 – 1000 Million metric tons/year
A framework for setting realistic expectations for water quality improvements

3. Strategies for reduction of agricultural chemicals and sediment
exported from fields to protect and improve water quality
 Stop movement at/near source
conservation practices, …
 Reduce chemical use
reduced N application rate, …
 Remediate in real-time
biofilters, cover crops, …
 Remove/retain in hydrologic network
constructed wetlands, ….
A framework for setting realistic expectations for water quality improvements

4. How do chemicals and sediment get into the stream … coastal areas?
They move with the WATER(and wind) !
A framework for setting realistic expectations for water quality improvements

5. A framework for setting realistic expectations for water quality improvements
Framework for setting expectations
Transport

6. A framework for setting realistic expectations for water quality improvements
CHEMICAL: All agricultural chemicals are distributed between sediment and water
This distribution is an important control on the transport of the chemical.

7. Conceptual framework of watershed hydrology and chemical behavior
“Natural” flowpaths to a stream
Slowflow
sourced
(groundwater,
wetlands, …)
Fastflow
sourced
(stormflow,
runoff, …)Different energies
Different interactions with surface and subsurface soil
Different mechanisms of chemical / sediment transport

8. Artificial flowpaths to the stream – surface and subsurface drainage
A framework for setting realistic expectations for water quality improvements

9. Artificial flowpaths to the stream – subsurface drainage
A framework for setting realistic expectations for water quality improvements

10. Conceptual space for water flowpaths to any agricultural stream
A framework for setting realistic expectations for water quality improvements
“Natural” stream

11. National Map of Primary Flowpaths on Cropped Land in the US
A framework for setting realistic expectations for water quality improvements

12. Conceptual framework of watershed hydrology and chemical behavior
Combining conceptual space for water
flowpaths and for chemicals along a
sediment-water distribution continuum

13. A framework for setting realistic expectations for water quality improvements
Examples of agricultural activities that can be used
for the protection or improvement of water quality
Trapping Practices
Terraces, Grassed waterways, Brims at edge of stream
Buffer filter strips, Cover crops
Tillage Practices
Conservation and no-till tillage
Contoured plowing
Drainage Practices
Controlled subsurface drainage
Biofilters on subsurface drains
Removal of subsurface drains and surface inlets to subsurface drains
Irrigation Practices
Reduced volume and energy of irrigation water
Chemical Use Practices
Reduction in chemical use
Use of chemicals with short environmental lifetimes
Set-Aside Land for Conservation
Conservation Reserve Program (Federal and state; e.g., USDA CRP)
Constructed wetlands

14. A couple of examples of setting
expectations for agricultural
activities based on this framework
Conceptual framework of watershed hydrology and chemical behavior
Two sediment-water end-members
100% associated with sediment
- soil particles
~ total phosphorus
~ DDT
100% associated with water
- water
- chloride
- nitrate
- atrazine
Assume no chemical transformation.

15. Conceptual framework of watershed hydrology and chemical behavior
A few example AMPs … Buffer strips
Fastflow Slowflow Drain flow
Solid Water Solid Water Solid Water
Buffer strip + +O O +O O O

16. Conceptual framework of watershed hydrology and chemical behavior
Example … No-till tillage
Fastflow Slowflow Drain flow
Solid Water Solid Water Solid Water
No-till + + O -O O -O

17. Conceptual framework of watershed hydrology and chemical behavior
Example … Reduction in use of the chemical
Fastflow Slowflow Drain flow
Solid Water Solid Water Solid Water
Reduction in use + + + + + +

18. A framework for setting realistic expectations for water quality improvements
Chemical behavior
Field: Engineered
hydrologic setting
Field: “Natural”
hydrologic setting
General effectiveness of
management practice

19. A framework for setting realistic expectations for water quality improvements
Nitrate in Chesterville Branch, MD
-- corn, soybean, nursery, …
-- groundwater-sourced
-- GW contaminated with nitrate

20. A framework for setting realistic expectations for water quality improvements
Sediment in DR-2 Drain, WA
-- grapes, hops, apples, corn, dairy, …
-- water from irrigation canal
-- excess irrigation creates runoff
-- SW contaminated with sediment+

21. A framework for setting realistic expectations for water quality improvements
Framework useful as a thinking, teaching, and policy tool
Protection
Improvement
Transport