United States Department of Agriculture 604-CPS-1

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NRCS reviews and periodically updates conservation practice standards. To obtain the current 

version of this standard, contact your Natural Resources Conservation Service State office or 

visit the Field Office Technical Guide online by going to the NRCS website at 

https://www.nrcs.usda.gov/ and type FOTG in the search field. 

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Natural Resources Conservation Service 

CONSERVATION PRACTICE STANDARD 

SATURATED BUFFER 

CODE 604 

(ft)

DEFINITION 

A subsurface, perforated distribution pipe used to distribute drainage system discharge beneath a

vegetated buffer along its length and discharge channel. 

PURPOSE 

Install the practice to achieve one or more of the following purposes: 

• Reduce nitrate loading from subsurface drain outlets through vegetation uptake and denitrification 

• Enhance or restore saturated soil conditions in riverine, lacustrine fringe, slope, or depression

wetland hydrogeomorphic classes 

CONDITIONS WHERE PRACTICE APPLIES 

This practice is applicable to lands with a subsurface drainage system adaptable to discharge in a

vegetated area. 

Apply this practice where the soils and topography of the vegetated discharge area can maintain a raised

water table without adverse effects to crops, channel banks, shorelines, or adjacent land. 

This practice does not apply to underground outlet systems. This practice applies to subsurface drainage

systems. If the system includes surface inlets, this practice applies only if the inlets are adequately

protected to prevent entry of soil and debris capable of plugging the distribution pipes. 

Do not use this practice to discharge septic system effluent or animal waste. 

CRITERIA 

General Criteria Applicable to All Purposes 

Conduct geologic and soil investigations to confirm— 

• Conditions, such as a restrictive layer, are present to create saturated conditions when water is

diverted from a subsurface drainage system. 

• The absence of pockets or layers of high hydraulic conductivity soil that could provide preferential

flow paths. 

• A minimum of 0.75 percent organic carbon (1.2 percent organic matter) in the top 2.5 feet of soil. 

• The absence of abandoned drain pipes in the buffer area that could continue to drain the buffer. 

• A minimum width of 30 feet vegetated buffer zone. 
Locate and design the system to maximize the amount of subsurface drainage water distributed to the

potentially saturated soil zone. Ensure there are no hydrologic trespass or other adverse impacts to

adjacent lands. Place the distribution pipe, at a minimum, 2 feet below the soil surface. 

Avoid placing the distribution pipe along any channels incised deeper than 8 feet, unless a slope stability

analysis shows an acceptable level of safety against saturated streambank failure. Slope stability analysis

may encompass geological investigations and reliance on local knowledge and field observations of bank

stability and lateral migration potential. Local knowledge and field observation relies on signs that imply

the existing bank does not exhibit an unstable slope and has adequate vegetative cover with a stream

channel that does not show recent lateral shifting in the floodplain. The NRCS Stream Visual Assessment

Protocol 2 (SVAP2) offers a bank condition element with descriptions of visual evidence of bank stability. 

For sites with obvious and observed bank stability problems, or if the proposed condition is predicted to

introduce bank stability problems, refer to NRCS Conservation Practice Standard (CPS) Streambank and

Shoreline Protection (Code 580) for protective measures, or alternatively, find a more stable site for the

proposed saturated buffer. 

Flow 

DRAINMOD, other appropriate model simulations, drainage mainline capacity, or drainage system

drainage coefficient with area drained can be used to determine drainage system capacity. 

Provide a positive hydraulic grade for drainage water to exit the saturated buffer distribution line.

Minimum saturated buffer design flow is 5 percent of drainage system capacity or as much as practical

based on the available length of the vegetated buffer. 

Use soil profile average saturated hydraulic conductivity, saturated buffer design flow rate, and hydraulic

heads available at the site to compute minimum buffer dimensions and length of distribution pipe required

to meet selected saturated buffer design flow. 

Water control structure 

Design a water control structure to maintain the target water table elevations over the distribution pipe

during the management period. Use the criteria found in NRCS CPS Structure for Water Control (Code

587). Locate the water control structure where it is accessible for water table observation and for

operation and maintenance. The structure location must not cause water to back up into a main or lateral

drainage system beyond a property line unless the upstream landowner provides written permission. 

Convey drainage water exceeding the design capacity of the saturated buffer through an overflow pipe to

a suitable stable outlet. Use nonperforated pipe for the overflow pipe for a minimum of 20 feet from the

water control structure to avoid draining the saturated soil zone around the water control structure. 

Distribution pipe 

Design the distribution pipe and overflow pipe according to the criteria found in NRCS CPS Subsurface

Drain (Code 606). Ensure the capacity of the distribution pipe is greater than the saturated buffer design

flow to ensure that the soil lateral flow capacity rather than the distribution pipe capacity limits saturated

buffer flow. 

Situate the distribution pipes on a topographic contour or grade to facilitate uniform ground water inflow to

the saturated zone. Add additional water control structures as needed for flow uniformity. The maximum

elevation difference between structures is 3 feet. 

Vegetation 

Establish permanent vegetation on the soil saturation area and any other disturbed areas to prevent

erosion and to utilize nitrogen from the drain water. The soil saturation area to be vegetated must be at

least 30 feet wide for the entire length of the distribution pipe. 

Refer to NRCS CPS Conservation Cover (Code 327), Critical Area Planting (Code 342), or Forage and

Biomass Planting (Code 512) for criteria on plant species selection; planting rates, methods, and dates;

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fertilization; and other factors to ensure a successful planting. Select the appropriate vegetative CPS

based on planned activities on the site, which can include secondary benefits such as habitat or hay

production as well as soil saturation. Do not allow livestock to utilize the vegetated buffer area. 

Additional Criteria to Reduce Nitrate Loading 

Provide a means to ensure saturated conditions within the high soil organic carbon region of the soil

profile when adequate drain flows exist. Design the system to maintain a water table within 12 inches of

the soil surface at the location of the distribution pipe near the water control structure during the

management period. For sites with adequate soil organic carbon at depths greater than 2.5 feet, the water

table setting may be lowered from the 12-inch threshold by the amount of additional depth. Maintain the

water control structure at the design level except when the water table must be lowered for providing an

adequate root zone for the crop, trafficability for field work, adverse weather conditions, or system

maintenance. 

Additional Criteria to Enhance or Restore Saturated Soil Conditions 

Design the system to replicate ground water levels shown in the “Water Features” report of the Water

Features section of the USDA Web Soil Survey report for the site. 

CONSIDERATIONS 

Consider using other practices and management systems in conjunction with this practice to achieve a

reduction of nitrate-nitrogen levels. Examples include NRCS CPSs Nutrient Management (Code 590),

Cover Crop (Code 340), Drainage Water Management (Code 554), Denitrifying Bioreactor (Code 605),

and Constructed Wetland (Code 656). 

Consider adding an envelope around the drain to improve exit flow. Refer to criteria in NRCS CPS

Subsurface Drain (Code 606). 

Consider examining 4-feet soil cores at various intervals along the width and length of the buffer area

when determining the existence of high conductivity soil layers that could provide preferential flow paths.

For example, take soil cores to a depth of 4 feet at every 200 feet of buffer length and visually inspect

them for sand and organic matter. Use Von Post method for assessment of organic matter. 

For enhanced denitrification, consider field verification of topsoil organic matter content rather than

reliance on rough (average or range) published data that is not specific for the site. 

For cost-effectiveness, consider locating the saturated buffer where it will intercept a subsurface drain

outlet draining at least 15 acres. 

Consider installing observation wells in the buffer midway between the distribution pipe and the receiving

channel or water body to facilitate water table documentation and water quality sampling. 

A saturated buffer may infiltrate less overland flow than a nonsaturated buffer. 

Where possible to maintain a water table at or near the buffer soil surface, planting the buffer to a mix of

hydrophytic species suitable for wet soil conditions will enhance nitrate removal and increase soil carbon

replacement at and near the soil surface. 

Installing a saturated buffer in locations where the water table is higher than the distribution line may result

in the distribution line becoming a drain rather than distributing the drainage water from the system. This

can happen where the land adjacent to the proposed saturated buffer is not adequately drained. 

Installation of this practice may enhance wildlife and pollinator habitats, with appropriate vegetation and

management. 

Install an anti-seep collar if piping of trench earthfill along the bypass pipe is a concern. Consider

measures to reduce the potential for root plugging of distribution lines by woody species. Set planted trees

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and shrubs back far enough that distribution lines will not be under the drip line of mature tree canopies.

Plant herbaceous species in areas over distribution lines. If the riparian area is currently in trees, either

establish an herbaceous zone outside the tree line for the water distribution area or remove only those

trees that inhibit installation of the distribution line. 

When practical, consider harvesting and removing green biomass to promote regrowth thus enhancing

additional nitrogen removal from the buffer area. Refer to NRCS CPS Forage and Biomass Planting (Code

512) for criteria on forage or biomass production. 

PLANS AND SPECIFICATIONS 

At a minimum, include— 

• A plan view of the layout of the water distribution system and saturated buffer area. 

• Profiles of the existing drain, distribution pipe, and outlet channel. 

• Details of required structures for water level control. 

• Vegetation establishment requirements. 

• Construction specifications that describe site-specific installation requirements. 

OPERATION AND MAINTENANCE 

Prepare an operation and maintenance plan that includes— 

• Planned water level management and timing. 

• Inspection and maintenance requirements of the water control structures, distribution pipes, and

contributing drainage system, especially upstream surface inlets. 

• Periodic removal of invasive trees or shrubs to reduce distribution line plugging. 

• If the site is to be monitored, monitoring and reporting requirements designed to demonstrate

system performance and provide information to improve the design and management of this

practice. At a minimum, record water levels (elevations) at the control structure, observation ports,

and if used, observation wells. Record water levels biweekly when a water table is present and

following precipitation events that result in high flows. 

REFERENCES 

Jaynes, D.B. and T.M. Isenhart. 2011. Re-saturating Riparian Buffers in Tile Drained Landscapes. A

Presentation of the 2011 IA‐MN‐SD Drainage Research Forum. November 22, 2011. Okoboji, IA. 

Jaynes, D.B. and T.M. Isenhart. 2012. Re-saturating Riparian Buffers using Tile Drainage. Unpublished. 

Jaynes, D.B. and T.M. Isenhart. 2014. Reconnecting Tile Drainage to Riparian Buffer Hydrology. Journal of

Environmental Quality 43:631-638. doi: 10.2314/jeq2013.08.0331. Advances in Agronomy 92:75-162.

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