1. Delaware Nutrient Load Reductions for Agricultural BMPs
Chesapeake Bay Program
Tributary Strategy Workgroup Meeting
November 7, 2006

2. Why are we here?
A brief overview of BMPs that are quantified in Delaware
Present water control structure overview and Nitrogen reduction data
Request that the CBP account for water control structure reductions

3. Chesapeake Bay Watershed
New York
Pennsylvania
Part one. The Chesapeake Bay is an estuary, where fresh and salt water mix. It is a very fertile place for things that grow.
About half of the water volume in the Bay is salt water from the Atlantic Ocean. The other half drains into the Bay from an enormous 64,000 square mile drainage basin or watershed.
Ninety percent of this fresh water is delivered from five major rivers: the Susquehanna (which is responsible for about 50% just by itself), the Potomac, the James, the Rappahannock and the York.
The Bay's watershed includes parts of six states: Delaware, Maryland, New York, Pennsylvania, Virginia and West Virginia, as well as the entire District of Columbia.
Additional information:
-The Chesapeake is the largest estuary in North America.
-More than 3,000 different species of plants and animals live here.
-The landscape which comprises the Bay watershed is made up of many interconnected basins, or watersheds. Within each watershed, all water runs to the lowest point - a stream, river or the Bay. On its way, water travels over the surface and across farm fields, forest land, suburban lawns, and city streets, or it seeps into the soil and travels as ground water. Large watersheds like the Chesapeake Bay are made up of many smaller watersheds across several states.
Maryland
Delaware
West Virginia
District of Columbia
Virginia

4. Over 90% of the Bay and its tidal rivers are impaired due to low dissolved oxygen levels and poor water clarity, all related to nutrient and sediment pollution.
Without oxygen and grasses, the Bay’s crabs, oysters, and fish cannot survive and thrive.
In 1998, the Chesapeake Bay and many of its tidal tributaries were added to the list of impaired waters, thus requiring the development of a TMDL to comply with the Clean Water Act. A TMDL is the maximum amount of a pollutant that a water body can receive and still meet water quality standards. It is calculated by totaling all the allowable loads of a single pollutant entering a body of water from all contributing point and nonpoint sources.
TMDLs also allocate the amount each pollutant source is allowed to release while still attaining water quality standards set by individual states and approved by EPA. These allocations are then regulated through enforcement of permit limits, principally directed at point source dischargers and the implementation of Best Management Practices (BMPs) for nonpoint sources.
The Chesapeake Bay’s main water quality impairment is its low dissolved oxygen (DO). Current state water quality standards require 5 mg/L of dissolved oxygen throughout all of the Bay’s waters – from the deep trench near the Bay’s mouth to the shallows at the head of the Bay. Even though the 5 mg/L standard is Baywide, scientists believe natural conditions dictate that in some sections of the Bay, such as the deep channel, Bay waters cannot achieve the current 5 mg/L standard. Additionally, scientists believe other areas, such as prime spawning areas, require higher levels of dissolved oxygen to sustain life.
In addition to dissolved oxygen, other Chesapeake Bay impairments include reduced light conditions and too much algae.
Impaired Water

5. Delaware -Total Maximum Daily Load and the Inland Bays Watershed
Promulgated in December 1998
Removal of all point sources of nutrient loading
Removal of 40-80% of nonpoint N
Removal of 40-65% of nonpoint P
Implementation through a Pollution Control Strategy
Low reduction area
High reduction area
TMDL developing

6. PCS Workgroup Members from various agencies
DNMC
DNREC: DWR & DSWC
NRCS
Sussex Conservation District
Kent Conservation District
University of Delaware Cooperative Extension
Mission: To devise a method to estimate how existing agricultural practices have already contributed to achieving the TMDL mandated nutrient load reductions …

7. PCS Workgroup Decisions
Calculations/recommendations based on best available science
Averages from several studies and/or ranges
Dependent on weather and site specific conditions
A lag time likely exists between practice implementation and benefit observation
Decisions assist in policy development and incentive based programs
Before actually discussing the decisions, we first have a little disclaimer...the decision that have been made were based on the best available science, and as you (the scientifice and technical advisory committee) know, science is always advancing...and we intend to update any and all of the following calculations as knew and better data become available to us.
In addition, we often averaged data from several years or from several studies in order to represent the average conditions from the Inland Bays watershed.
In doing so, we hope to suppress any effects of site specific conditions like (topography, soil type, crop production intensity, excess manure generation) or weather conditions (like drought or hurricanes) from the study period and location, however, this possibiltiy can not be ruled out.
And finally, we would like to recognize that....lag time... which we can not currently estimated because not all nutrient fate and transport processes are well understood at this time
Despite this disclaimer, ...

8. Cropland Loading Rates
Averaged data from two local studies
Ritter (1986)
TN: lbs/acre/yr
TP: 0.8 lbs/acre/yr
Ward (2001)
TN: lbs/acre/yr
Average loads used
TN: lbs/acre/yr
First of all, the group needed to decide on loading rates to assign to cropland...the chosen value will be used in numerous other reduction calculations for other bmps
Ritter's values were based, in part, on actual water quality sampling during our baseline period. These values were very similar to those generated by the Us Army Corp of Engineers Hydrodynamic and Water Quality Model for the Inland Bays.
Ward's updated Ritter's initial study....these both can be considered appropriate for the baseline period

9. Agricultural BMPs Considered
Reduced Commercial Fertilizer Application
Cover Crops
Conservation Reserve Program Practices
Conservation Reserve Enhancement Program Practices
Water Control Structures
Poultry Compost and Manure Storage Sheds
Manure Relocation and Alternative Use
Phytase
Nutrient Management Plans
The group attempted to establish nutrient loading reductions for 9 agricultural Best Management Practices which are listed here. First, I'll discuss whether or not we were actually successful at establishing a reduction efficiency for each of these practices. A reduction efficiency is a percentage that indicates who much a particulate BMP reduces the nutrient load to the receiving water body. (So if I say that a BMP has a reduction efficiency of 50%, that means that the nutrient load coming from an agricultural field will be cut in half prior to entering the stream due to the implementation of that BMP.) For the BMPs that we found efficiencies in the literature, I will then show you how we have estimated the load reduction to the stream.

10. Water Control Structures in place
N reduction to stream (lb/yr)
= x x
Inland Bays watershed
51 Structures, 1,530 acres treated = 29TN/day, 10,603TN/yr
Nanticoke River watershed
12 Structures, 175 acres treated = 3.3 TN/day, 1,213 TN/yr
Cropland loading rate (lb/acre/yr)
Acres treated by BMP
Efficiency (%)
WCSs hold the water table high in the soils during the winter, which is when more than half of the water and nutrients leave the fields. It is during these times that water control structures promote dentrification and lower nitrate concentrations in ground and surface waters.
***the acreage we have here is not the number of acres of wcs, but the number of acres treated by wcs, which is the total land area drained to that structure

11. Water Control Structures
Use the N reduction efficiency of 33% reported by Gilliam and Skaggs (1986)
Currently, there is little research to support a P reduction efficiency for water control structures
N reduction to stream (lb/yr)
= x x
WCSs hold the water table high in the soils during the winter, which is when more than half of the water and nutrients leave the fields. It is during these times that water control structures promote dentrification and lower nitrate concentrations in ground and surface waters.
***the acreage we have here is not the number of acres of wcs, but the number of acres treated by wcs, which is the total land area drained to that structure
Cropland loading rate (lb/acre/yr)
Acres treated by BMP
Efficiency (%)

12. Water Control Structures
NRCS Code # 587
Proper installation and maintenance
N-reduction due to volume flow reduction
Storm events – high base flow
N-reduction due to concentration reduction
P-reduction due to sediment transport reduction
WCSs hold the water table high in the soils during the winter, which is when more than half of the water and nutrients leave the fields. It is during these times that water control structures promote dentrification and lower nitrate concentrations in ground and surface waters.
***the acreage we have here is not the number of acres of wcs, but the number of acres treated by wcs, which is the total land area drained to that structure

13. Progress to Date from Agriculture
NMPs (9,225 acres)
Phytase (43,597 acres)
Manure (10,886 tons)
Water Control (55 structures)
Wetlands (65 acres)
Forest Buffers (92 acres)
Grass Buffers (54 acres)
CRP (200 acres)
Cover Crops (4,203 acres)

14. Reductions Achieved from BMPs on the Ground
Stormwater
Septic
Agriculture
23%
88%

15. Future Agricultural BMP Goals
NMPs (41,523 acres)
Phytase (NA)
Manure (14,032 tons)
Water Control (0 structures)
Wetlands (5,263 acres)
Forest Buffers (4,712 acres)
Grass Buffers (0 acres)
CRP (0 acres)
Cover Crops (32,231 acres)

16. Questions & Comments