COMPLETEING A PRELIMAINRY ASSESSMENT FOR AG. WATER SUPPLY PONDS

COMPLETEING A PRELIMAINRY ASSESSMENT FOR AG. WATER SUPPLY PONDS

Water Quantity and Conservation #1

Use land according to its capability and treat it according to its needs

Use management to gain the most agricultural benefit from precipitation and shallow groundwater

Improve water use efficiency

Keep runoff clean

Capture runoff and use it on the farm

Farmers, Consultants and Partners #1

NRCS wants the opportunity to assist you in development of a conservation plan that adds value to your land.

Why is NRCS ability to assist you with pond development limited to a preliminary site assessment?

Time- people w/ pond experience, broader mission

Money- program funds targeted, demand v. supply

Red tape- the federal compliance burden

Farmers, Consultants and Partners #2

This process is for ag. water supply ponds- irrigation, stock watering, wash water and cooling water.

Do you need to use this process? NRCS workload priorities might be

directed elsewhere when you request assistance.“ I won’t be able to assist you right now, but I’d like

to get some information about your needs and if time becomes available we’ll get in contact with you.”

NRCS and District folks- #1

Are we getting back into the pond business?

Is this the only training I’m going to get? Please don’t over-think this assessment

Off-site evaluationNo lay-outNo design

NRCS and District folks- #2

Use pond interest to engage in on-farm planning.“Can I get you to go on site to look at my place?”

Prelim. Site Assessment “pre-planning service” evaluate candidate site’s natural resources for

capability of land to support pond development

explain potential regulatory issues

enable early identification of problems with a proposed site that can be changed or solved because the idea is still being developed

help farmer’s develop ponds they need

will save farmer’s time in the overall process by ensuring practical alternatives, site limitations and regulatory issues are considered before large investments of time or money are made

Not all sites are good candidates: Soils and geology can cause limitations

Size of drainage area

Flood hazards

Unique cultural or environmental features

Ratio of drainage area to pond surface area affects water level At least 10:1. Not more than 30:1. Mid-range is ideal.

Good soil conservation in the drainage area is important

Rules of Thumb #1

Rules of Thumb #2

Irrigation storage: at least 1.3 to 1.5 acre-feet of storage per acre irrigated

Evaporation and seepage losses: 2.5 to 4 ft. per irrigation season

Beef cattle require at least 15-20 gallons per animal per day.

Pond may not be best alternative for livestock water supply.

NRCS has published technical references that can be used to support planning and design:

National Eng. Handbook, Ponds and Reservoirs

NC Irrigation Guide

Conservation Practice Standard: Pond (378)

Use ArcMapNavigate toArea of Potential Pond Site

Define Area of Interest

Bare Earth Data Converted to Tin

Tin Converted to 5ft Contours

Site Characteristics Question 1:Estimated

Drainage Area

For THIS Example - 10:1 Ratio of Drainage Area to Surface Area of Pond Needed

IDEAL = 20:1 Ratio

ASSUMPTION:

68 Acre Drainage Area=

6.8 Acre Pond

Site Characteristics Question 2:

Estimated Pool Area

Site Characteristics Question 3:Estimated Depth of Water

Elevation Difference - Lowest Point to Top of Pool Area

955’

931’

Site Characteristics Question 4:Estimated Embankment Height

Add 5ft to Embnakment Height for Freeboard and Spillway

960’

931’

Site Characteristics Question 5: Estimated Length of Dam

Look Downstream

What Hazards are Observed?

• Measure the Distance to Any Downstream Hazards • Create .pdfs to Attach to Assessment Showing Potential Hazards

Following General Guidelines Referenced in USDA: Ponds – Planning, Design, and Construction

Based on Embankment Height of 29ft =

Dam Width of 14ft

Ass

ume

3:1

– O

utsi

de T

oe

Assum

e 3:1 – Inside Toe

94 ft 94 ft

Estimated 188 ft of the Stream Filled by Embankment

Using Soil Data Viewer

ArcMap or Toolkit Environment

Use the NC Floodplain Mapping Program Stream

Data to Determine if a Blue Line Stream Exists

Calculate Feet of Stream Inundated by Pond

Length of NCFPMP Stream Inside Pond

MINUS

Length of Inside Toe

631 ft – 94 ft= 537 ft

Does the potential pond area fall within the boundaries of the property owned by the person?