Harvesting Rainwater for Animals

Ginger Easton SmithEmily Moench

Texas AgriLife Extension

How to Collect Rainwater

P 0.6 gallons per square foot of roof per 1” rainfall

Gutters and Downspouts

Weight – 8.33 lb/gallon7.5 gallons per cubic foot

Rainfall is captured off a small barn into 300 gallon recycled containers and used to water chickens, ducks and Guineas

These watering pans are connected to the 300 gallon containers by a

water hose.

Deciding Factors for Water Needs

• Kind of animal• Number of animals• Annual rainfall and length of time between

rain events (longest usual dry period)• Whether or not wildlife have access to the

water

Example: Water demand for 2 horses

• I have 2 mature horses and live where the average rainfall is 31 inches of rain per year and most dry spells are not 2 months long.

• How much roof surface do I need and • How large a catchment tank

do I need?

Average Daily Consumption of water by various Livestock Species

Species Gallons of Water per DayCattle 7 to 18 gallonsHorses 8 to 18 gallons Sheep and Goats 1 to 4 gallons

General rule: Provide 2 gallons of water per 100 pounds of body weight daily.

Water needs for 2 horses• Daily maximum water requirements

18 gallons x 2 horses= 36 gallons/day

• Monthly requirement30 days x 36 gallons = 1,080 gallons/month

• Storage needed for dry spells1,080 gals. x 2 months supply = 2,160 gals. minimum storage needed, so…at least a 3,000 gallon tank

How Much Water Can You Capture?

Rainfall x Catchment Area x Conversion factor = Supply (Inches) x (Square Feet) x 0.623 = (Gallons)

Example: 1 inch rain falls on a 10’ by 20’ roof1” x (10 x 20) = 200 sq’ x .6 (0.623 rounded off) =

120 gallons

Catchment area

• Footprint of the building

Roofs and Collection Surfaces

Is my barn big enough to catch needed water?

If the roof measures 20’ x 60’ (footprint) how much will I catch per 1” rain?

Reminder: Rainfall x catchment area x conversion factor = supply

1” rain x 1,200 sq.ft. (20’ x 60’) roof area = 1,200 1,200 x .6 (conversion factor) = 720 720 gallons per inch of rainfall

If the average monthly rainfall is 2.5” then how much will I catch?

720 gals. x 2.5” = 1,800 1,800 gallons could be captured in an average

monthSo barn roof is big enough to catch needed 1,080

gals. water

How Big A Storage Tank Do I Need?• Average monthly rainfall: 2.5” or for the

20’ x 60’ barn = 1800 gallons• The dry spells seldom last 2 months but we

need to store a minimum of 2 months supply to protect us from extended drought

• So, 2160 gallons would be sufficient (2 months x 1080 gals. = 2160 gals.)Rounded up to 3000 gallon tank

Just to be on the safe sideOther considerations:• Efficiency of roof and collection system• Evaporation from watering device or trough• Water that might be diverted in a first flush, if

attached• Water used to wash horses, water pets, wash

hands or for other needs

So, 4,000 gallons of storage or more would be preferred.

How Much Rain Will It Take To Fill The 4,000 Gallon Storage Tank?

• Roof area – 20’ x 60’ = 1,200 sq’• 1,200 x .6 = 720 gallons per 1” rain• 4,000 gallon tank divided by 720 = 5.6• 5.6” of rain would fill the 4,000 gal. tank

Dry Line vs. Wet Line

Dry Line

Minimum of 18 inches difference in height required from the bottom of the gutter to where the water goes into the storage tank.

Wet Line

T he Other Par ts

P Gate valve and faucetsP .434 lb of Pressure/column ft.

Overflow PipeThe overflow allows water to run out of the tank when it is full rather than backing up into the gutter

Pump and Pressure TankShallow well pumpand Pressure tank orOn-Demand Pump

Screens

Rainwater Collection System

Texas State University’s Freeman Ranch Wildlife Water Guzzler – 20’ x 20’ Roof And Two 1500 Gal. Tanks. The Fence Keeps Livestock Out.

The Larger Tub May Attract Mosquitoes Unless Mosquito Dunks Are Used. The Cover Over The Float Prevents Raccoon From Damaging The Guzzler.

When animals drink the water the float drops down and allows water to run –just as in a commode

Donkeys drinking from a watering trough with a float connected to it to keep it full of water.

http://rainwaterharvesting.tamu.edu/

Thank you to Mr. Billy Kniffen for use of slides

The calculator on the website provides average monthly rainfall for each location marked