United States Department of Agriculture 646-CPS-1

NRCS, NHCP

January 2024

Notice of Proposed Changes to the National Handbook of Conservation Practices 

for the Natural Resources Conservation Service

[Docket No. NRCS-2023-0022]

PROPOSED FULL TEXT FOR PRACTICE STANDARD CODE 646

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. 

USDA is an equal opportunity provider, employer, and lender.

Natural Resources Conservation Service 

CONSERVATION PRACTICE STANDARD 

SEASONAL WATER MANAGEMENT FOR WILDLIFE 

CODE 646 

(ac)

DEFINITION 

The seasonal inundation of lands with water to provide specific life cycle needs for fish or wildlife. 

PURPOSE 

This practice is used to: 

• Provide essential habitat elements for wildlife such as shorebirds, waterfowl, wading birds,

mammals, fish, reptiles, amphibians, and other species that require standing or pooled water for a

portion of their life cycle, by managing the depth and duration of inundation. 

CONDITIONS WHERE PRACTICE APPLIES 

Lands that can be inundated by active management of water using existing or planned infrastructure

including dikes, ditches, pumps, and water control structures. 

Floodplains where seasonal flooding is needed to provide refuge for native fish during high flow periods. 

This practice does not substitute or replace — 

• Conservation Practice Standard (CPS) Dike and Levee (Code 356) and (CPS) Structure for Water

Control (Code 587) when structural practices are needed to impound or hold water. 

• Conservation Practice Standard (CPS) Watering Facility (Code 614), applied to provide sources of

drinking water for wildlife. 

• CPS Constructed Wetland (Code 656) intended to treat point and nonpoint sources of water

pollution. 

• CPS Wetland Restoration (Code 657) applied to rehabilitate a degraded wetland where the soils,

hydrology, vegetation community, and biological habitat are returned to a close approximation of the

original conditions. 

• CPS Wetland Creation (Code 658), applied to create wetland functions on a site that was not a

wetland historically. 

• CPS Wetland Enhancement (Code 659) intended for modification of an existing wetland where

specific attributes are targeted by management objectives, possibly at the expense of other

attributes, or the rehabilitation of a degraded wetland where the result is a wetland that is different

than what previously existed on the site. 

• CPS Wetland Wildlife Habitat Management (Code 644), applied to maintain, develop, or improve

existing wetland habitat by means other than managing the level and duration of inundation. 

• CPS Fish Pond Management (Code 399) installed for the purpose of managing impounded aquatic

habitat and water quality for the production of fish. 
CRITERIA 

General Criteria Applicable to All Purposes 

Apply an NRCS State approved habitat evaluation or assessment (e.g., Wildlife Habitat Evaluation Guide)

to identify habitat-limiting factors that can be addressed by managing inundation on the planning area. 

The site must be capable of supporting surface inundation for the prescribed period. 

Water supply for planned periods of inundation must be adequate (e.g., available and reliable). 

Water supply for planned periods of inundation must be of acceptable quality for intended wildlife. 

Dewatering must be possible within a prescribed schedule to meet both the target habitat conditions and

future management needs. 

Maintain the appropriate depth over most of the planning area during periods of scheduled inundation. 

Utilize, decommission, or modify existing drainage systems to achieve the intended purpose. 

Duration of inundation must be sufficient to meet the identified life cycle need (e.g., extend throughout the

local breeding period). 

Surrounding upland habitat must be of sufficient quality and quantity to support the complete life-cycle

requirements when amphibians are the objective. 

Water control and management structures must prevent predatory fish access to areas planned for

amphibian breeding habitat. 

CONSIDERATIONS 

Nearly level sites will allow for larger units while keeping planned water depths within a consistent range

over most of the unit and while more undulating sites will provide more diversity of water depths. 

The timing of flooding and drawdown, as well as the type of drawdown, will affect future management of

the site (e.g., planting the next crop in sequence or moist soil plant species composition). 

Burning, disking, or other surface disturbance on an appropriate schedule can set back succession,

control the growth of undesirable plants and encourage desirable plant communities on areas that will not

be managed annually for agricultural purposes. 

Consider tolerance of plants to flooding and salinity. 

Nutrient and pesticide residues may affect plant species composition and the site’s capability to grow

desirable plants. 

Adding and holding water on a site may impact adjacent habitats and crops. 

Implementing this practice may increase movement of dissolved and suspended substances to

downstream surface waters and groundwater . 

The practice may affect downstream flows or aquifers that would affect other water uses or users. 

The practice may function as a link in a habitat corridor that aids the site’s use and colonization by wetland

flora and fauna. 

The composition, structure, and extent of surrounding upland vegetation may influence habitat functions. 

Installation of vegetated buffers on surrounding uplands may improve water quality in the shallow water

area. 

-CPS-2

NRCS, NHCP

646

January 2024
Implementing this practice may raise downstream water temperature, causing detrimental impacts to

associated aquatic and terrestrial communities. 

Soil disturbance may increase the probability of invasion by unwanted plant species. Increasing water

depth and duration may be used as a method to control unwanted vegetation. 

Human and livestock activities in and surrounding the practice may disturb wildlife, thereby decreasing

habitat suitability and function. Vegetative screens, fences, or gates are means of reducing unwanted

disturbance. 

Inundation of soils and vegetation with water may create anaerobic conditions, leading to increased

methane emissions. 

PLANS AND SPECIFICATIONS 

Practice designs will specify the targeted species, desired water depths and duration and timing of

inundation, as well as drawdown dates, rates, and methods. 

Practice designs will specify the supporting practices required to implement the practice, as applicable. 

Specifications should be recorded using state approved specifications sheets, narrative documentation in

the conservation plan or other acceptable documentation. 

OPERATION AND MAINTENANCE 

The following actions must be carried out to ensure that this practice functions as intended throughout its

expected lifespan. These actions include routine activities in the application and use of the practice

(operation), and repair and upkeep of the practice (maintenance). 

• Any use of fertilizers, mechanical treatments, prescribed burning, pesticides and other chemicals

must not compromise the capability of the practice to provide habitat for the target species. 

• Monitor and repair structural components as necessary, particularly after flood events. 

• Repeat habitat evaluation or assessment procedures to determine habitat quality provided and

adjust water management as necessary to achieve habitat objectives. 

REFERENCES 

Frederickson, . L. H and F. A Reid. 1988. Waterfowl Management Handbook. US Fish and Wildlife

Service, Leaflet 13, 258 pp. 

Fredrickson, L.H., 1991. Strategies for Water Level Manipulations in Moist-soil Systems, 13.4.6, Gaylord

Memorial Laboratory, School of Natural Resources, University of Missouri-Columbia., Puxico, MO. 

Helmers, D. 1992. Shorebird Management Manual. Western Hemisphere Shorebird Reserve Network,

Manomet, MA 58 pp. 

Kaminski, R.M., J.B. Davis. 2014. Evaluation of the migratory bird habitat initiative: Report of Findings.

Forest and Wildlife Research Center, Research Bulletin WF391, Mississippi State University. 24 pp. 

Kingsbury, B. and J. Gibson. 2002. Habitat Management Guidelines for Amphibians and Reptiles of the

Midwest. Partners in Amphibian & Reptile Conservation, Ft Wayne IN, 57 pp. 

Nelms, K. D, B. Ballinger and A. Boyles, Eds, 2007. Wetland Management for Waterfowl Handbook.

Mississippi River Trust, USDA Natural Resources Conservation Service, and US Fish and Wildlife Service,

132 pp. 

-CPS-3

NRCS, NHCP

646

January 2024
Sieges, M.L., J.A. Smolinsky, M.J. Baldwin, W.C. Barrow, Jr., L.A. Randall, and J.J. Buler.. 2014.

Assessment of Bird Response to the Migratory Bird Habitat Initiative Using Weather-Surveillance Radar.

Southeastern Naturalist 13(1):G36-G65. 

Smith, L. M. and R. L. Pederson. 1989. Habitat management for migrating and wintering waterfowl in

North America. Texas Tech University Press, 574 pp. 

Stafford, J. D., R.M. M. Kaminski, K. J. Reinecke and S. W. Manley. 2006. Waste Rice for Waterfowl in the

Mississippi Alluvial Valley. Journal of Wildlife Management 70 (1): 61–69. 

USDA-NRCS and Wildlife Habitat Council. 2007. Temporarily flooded wetlands. Fish and Wildlife Habitat

Management Leaflet No. 47. Washington, D.C. 

Zinke, B. M, “Comparison of Small Mammal Communities in Ephemeral Wetlands and Wet Meadows

during Drought.” (2014), Maters Theses, Fort Hays State University

-CPS-4

NRCS, NHCP

646

January 2024