Managing Delmarva Agricultural Drainage Ditches for

Water Quality Protection

College of Agriculture and Natural Resources

Agricultural drainage ditches are essential for draining storm and subsurface water from farmland on the Delmarva Peninsula. Ditches are unique ecosystems, having the features of both streams and wetlands. Ditches often provide lman.

the only wetland and aquatic habitats process nutrients and other pollutants that result from farm activity.  The engineered nature of

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ditch systems enables them to handle a concentrated

exposed b y ditch c lean-out

Photo by Br

ian Neede

on farmland.  They also carry, store, and

level of pollutants and provides opportunities for management not available with natural streams. Improving ditch management not only aids in agricultural efficiency, but also provides agricultural producers with important opportunities for protecting

Needelman.

water quality.

Photo by Brian

Drainage and water-control structures A well-designed ditch provides good water movement and drainage while maximizing water conservation for crop production. Water-control (or flow-control) structures have horizontal boards that allow managers to control the depth of water in the ditch and the flow rate. These structures increase

g the water structure raisin Water-control e e soil surfac table to near th

Ditches carry pollutants from both nonpoint sources such as in runoff and point sources such as manure storage areas.

water retention during winter and summer, improve crop yields and wildlife habitat, and decrease the quantity of pollutants that move downstream.

Ditch clean-out

restores a ditch’s capacity to carry water by removing the collected sediment. Dredging often

Two-stage ditch engineering

exposes sediment with a low capacity to capture pollutants such as phosphorus and some herbicides; in

Ditches may naturally form or be engineered for a two-stage geometry, which consists of an inset channel

to dredge is when they expect amounts of these

and a small vegetated bench that serves as a floodplain.

pollutants to be low. On the Delmarva Peninsula,

Although building a two-stage channel rather than a

most ditches are dredged on a 10- to 30-year cycle.

traditional ditch channel requires more excavation,

Excavated materials are generally deposited on ditch

the two-stage channel improves conveyance capacity,

banks and in adjacent fields where they may be

provides water quality and other ecological benefits,

susceptible to erosion.

and is more self-sustaining. When these benches form

Andy War d.

these cases, the best time for agricultural producers

naturally, it may be preferable not to disturb them

Photo co

urtesy of

Ditch wit h inset ch annel and veget ation benches

during ditch-dredging operations.

Nonpoint and point sources Ditches may carry pollutants from

Photos by Brian Needelman.

both nonpoint sources such as field runoff Ward.

and concentrated sources such as farm

Vegetated benches formed naturally

te Photo cour

sy of Andy

production areas, highways, or towns. Ditches that drain on-farm point sources and carry high pollutant loads can be targeted with gineered hannel Ditch en d inset c n a s e h c ben

for conservation practices. Ditches can transport surplus nitrogen and phosphorus

Photos by Br

Cleaning out or dredging a ditch

ian Needelm

an.

Ditch clean-outs

Most ditches capture more phosphorus than they lose over time.

Photo

s cour

from agricultural systems. By slowing

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f Cha

d Pen

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water movement, water-control structures are effective at decreasing nutrient losses. Increasing retention time of ditch water allows for greater nitrogen removal and promotes the accumulation of sediment-bound forms of phosphorus. Other methods of nutrient control include riparian buffers, filters (reduction curtains, infiltration filters), and improved management of adjacent fields to lower the potential for transfers

Filters containing phosphorussorbing material

from fields to ditches.

phosphorus, keeping it from flowing downstream. Engineered systems in which drainage water passes through phosphorus-sorbing materials, such as

an. Photo by Brian Needelm

gypsum, drinking water treatment residuals, or acid mine drainage residuals, can potentially remove large percentages of phosphorus as well as sediment, heavy metals, and other pollutants.

ter ch with stagnant wa Algal bloom in a dit

Phosphorus-sorbing materials Ditches that drain sites containing very high levels of phosphorus likely themselves carry high levels of phosphorus. A large portion of this load is transported in the dissolved form; management practices that reduce particulate phosphorus are ineffective at reducing dissolved phosphorus. “Phosphorus-sorbing” materials soak up dissolved

Ditch sediments and soils Ditch sediments and soils react with ditch waters through biological and chemical processes and influence the concentrations and forms of phosphorus. Sediments and soils within ditches can capture dissolved and particulate phosphorus from drainage water and suspended sediments. This phosphorus may be released back into the drainage water from the ditch sediments and soils through disturbance, erosion, or leaching. Most ditches capture more phosphorus

Photo by Brian

Needelman.

Iron monosu lfides

indicating high ly anoxic cond itions

Ditch soil

than they lose over time. However, if management

nitrogen from ditch water. Anoxic conditions also

practices in a watershed cause a decrease in

lead to cycling of iron and sulfur minerals, with both

phosphorus concentrations entering a ditch, then the

positive and negative consequences for water quality.

ditch sediments and soils may become net phosphorus sources and should be removed or treated.

Ditch vegetation Herbaceous vegetation in ditch channels serves

Anoxia in ditches Unlike most streams, “healthy” ditches undergo

to filter pollutants, stabilize sediments and soils, cycle nutrients, and provide habitats for various

periodic losses of oxygen (anoxia). This occurs due to

organisms. Ditch vegetation may be killed or stressed

water stagnation, continuous soil saturation, and the

by becoming covered with too much water and by

presence of lots of organic matter. Anoxic conditions

the loss of soil oxygen. Stray woody vegetation may

and organic matter availability favor denitrification,

reduce flow capacity in the ditch channel or clog it

which is the transformation of nitrogen from a

entirely. The Maryland Department of Agriculture

dissolved form to nitrogen gases and which serves

developed and field-tested a “weed wiper,” a tool that

as an important mechanism for removing inorganic

selectively applies herbicides to woody vegetation

Photo courtesy

of David Ruppe

rt.

Ditch vegetation may be killed or stressed by becoming covered with too much water and by the loss of soil oxygen.

Stray woody vegetation may reduce flow capacity in the ditch channel or clog it entirely.

in ditches, replacing the common practices of lman. ian Neede

mowing and broad herbicide applications. With this technology, nonwoody vegetation remains in

Photo by Br

place to retain sediment, to stabilize soils and banks, and to provide ecosystem habitats.

External ditch management practices

ritus n and det

io h vegetat Ditch wit

For management practices established outside of the ditch itself, there is generally a trade-off between taking more land out of production and increasing environmental benefits. Since these practices take valuable land out of production, landowners are often compensated financially. from their natural floodplains, thereby removing natural sediment retention mechanisms. Floodplains may be re-established within drainage ditch networks to serve as natural sediment and pollutant retention mechanisms and to provide habitat. Options for performing this improvement include: • Benches within larger ditches

Algal turf scrubber

Photo courtesy of Edwin

Remsberg.

Ditching and channelization disconnect waterways

Algal Turf Scrubbers Researchers at the University of Maryland and the

• In-stream and riparian wetlands

U.S. Department of Agriculture Agricultural Research

• Lowering of the floodplain to reconnect it to a ditch

Service, in cooperation with the Maryland Department

• Redesigning ditches using natural channel design

of Agriculture, are evaluating the use of Algal Turf

principles, and • Establishing riparian buffers.

Scrubbers to remove nutrients from ditches and also to produce biomass that can be used as a feedstock for biofuels.

Drainage ditches are an integral part of many agroecosystems, functioning to improve field drainage for crop production, but also serving as key pathways of nutrient export.

Resources

MDA Cost-Share Program (MACS). For more

• The Ditch Project maintains a webpage at http://

information, download an MDA pamphlet entitled

sawgal.umd.edu/DrainageDitches/index.htm. The

“Cost-share assistance for public drainage

page includes resources from the 2006 Ditch

associations” at http://www.mda.state.md.us/pdf/

Project Field Tour and Symposium, including the

MDA_PDA_bro_proof2.pdf.

Field Tour Guide and symposium abstracts and presentations. • The 2007 July/August edition of the Journal of Soil and Water Conservation (Vol. 62, No. 4) provides a special section on drainage ditches that includes

• Delaware also has a system of cooperatively managed ditches, termed tax ditches. For more information, see http://www.swc.dnrec.delaware. gov/Pages/TaxDitches.aspx. • Federally, the U.S. Department of Agriculture

an overview paper with an extensive reference

(USDA) administers many ditch-related programs.

list of ditch-related literature and 15 original

Cost-share assistance programs are generally

papers covering fundamentals, methodologies,

administered through the USDA Natural

and case studies.

Resources Conservation Service (NRCS) such

• The University of Maryland houses a ditch soil

as the Environmental Quality Incentives Program,

monolith collection. Soil monoliths are vertical

the Conservation Security Program, the Flood

cross sections of a soil profile permanently

Plain Easement Program, the Farmland Protection

mounted on a wooden board. These monoliths

Program, and the Wetlands Reserve Program.

are available for viewing and for loan for ditch-

The USDA Farm Service Agency administers

related presentations (contact Brian Needelman

the Conservation Reserve Program and the

at 301-405-8227).

Conservation Buffer Initiative. The USDA-NRCS National Engineering Field Handbook includes

• In Maryland, most large ditches are owned and maintained by Public Drainage Associations and Public Watershed Associations. The Maryland

chapters on water table control, wetland restoration, and drainage management (available online at: http://www.info.usda.gov/CED/).

Department of Agriculture (MDA) is responsible for regulating and overseeing the drainage and

• The Agricultural Drainage Management Systems

watershed associations. Managers must also

Task Force is a USDA technical work group

conduct annual walking inventories, leading to

addressing water management issues on

formal operation and maintenance plans. Water

agriculturally drained lands (http://extension.osu.

control structures are cost-shared through the

edu/~usdasdru/ADMS/ADMSindex.htm).

Our long-term goal is to develop and implement improved ditch management practices.

• The Agricultural Drainage Management Coalition

Innovation Grants program (USDA-EQIP), the

is an organization of private companies working to

Cooperative Institute for Coastal and Estuarine

promote drainage water management to reduce

Environmental Technology (National Oceanic and

the nutrient enrichment of water bodies, protect

Atmospheric Administration), and the Keith Campbell

against droughts, and enhance wildlife habitat

Foundation for the Environment.

(http://www.admcoalition.com/).

The Ditch Project The Ditch Project is a collaboration among University of Maryland, College Park; University of Maryland Eastern Shore; USDA Agricultural Research Service in University Park, PA; stakeholder farms; and University of Maryland Cooperative Extension. We study the science and management of nutrient

Partners • The Ditch Project (Lead Investigators: Brian Needelman, Peter Kleinman, and Arthur Allen) • University of Maryland • University of Maryland Eastern Shore • USDA Agricultural Research Service Pasture Systems and Watershed Management Research Unit

losses from ditch-drained agroecosystems and work with farmers and government agencies to

• Chesapeake Research Consortium

develop and assess improved ditch management

• Maryland Department of Agriculture

practices. Drainage ditches are an integral part of many agroecosystems, functioning to improve field drainage for crop production, but also serving as key pathways of nutrient export. Our long-term goal is to develop and implement improved ditch management practices that increase economic profitability and reduce nutrient and other pollutant losses to the

• Mid-Atlantic Association of Professional Soil Scientists • USDA Mid-Atlantic Regional Water Program • Maryland Water Resources Research Center • Design and printing of this document was made

Chesapeake Bay and other impaired water bodies. Our

possible through the support of the Keith Campbell

primary external funding sources have been the USDA

Foundation for the Environment.

National Integrated Water Quality Program, the USDA Capacity Building Program, the USDA Conservation

Authors • Brian A. Needelman, Associate Professor, Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742; 301-405-8227; [email protected]. • Arthur L.  Allen, Associate Professor, University of Maryland Eastern Shore, Department of Agriculture, Food, and Resource Sciences, Princess Anne, MD 21853; 410-621-2876; [email protected]. • Peter J.A. Kleinman, Soil Scientist, USDA-ARS Pasture Systems and Watershed Management Research Unit, University Park, PA 16802; 814-865-3184; [email protected]. • Ray B. Bryant, Research Leader, USDA-ARS Pasture Systems and Watershed Management Research Unit, University Park, PA 16802; 814-863-0923; [email protected].

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