Find the catchment arealength ft x width ft= catchment area ft2

length m x width m= catchment area m2

60 ft18.3 m

57 ft 17.4 m

46 ft14 m

22 ft6.7 m

60 ft18.3 m

22 ft6.7 m

60 ft x 22 ft= 1320 ft218.3 m x 6.7 m= 122.6 m2

Find the catchment area

35 ft 10.7 m

46 ft14 m

35 ft x 46 ft= 1610 ft210.7 m x 14 m= 149.8 m2

Find the catchment area

60 ft18.3 m

57 ft 17.4 m

46 ft14 m

22 ft6.7 m

1320 ft2 + 1610 ft2 = 2930 ft2122.6 m2 + 149.8 m2 = 272.4 m2

Find the catchment area

Possible Volume from RunoffCatchment area ft2 x rainfall ft x 7.48 gal/ft3 =

maximum runoff in gal

Catchment area m2 x rainfall mm = maximum runoff in liters

Volume from Runoff1320 ft2 x 3.58 ft x 7.48 gal/ft3= 35347.49 gal122.6 m2 x 1092 mm= 133879.2 l

Possible Volume from RunoffCatchment area ft2 x rainfall ft x 7.48 gal/ft3 = maximum runoff in gal

Catchment area m2 x rainfall mm = maximum runoff in liters

Avg. rainfall in Cincinnati= 43 in43 in- = 3.58 ft43 in = 1.092 m1 ft = .3048 m

22 ft6.7 m

catchment area60 ft x 22 ft= 1320 ft218.3 m x 6.7 m= 122.6 m2

60 ft18.3 m

Volume from Runoff

35 ft 10.7 m

46 ft14 m

catchment area35 ft x 46 ft= 1610 ft210.7 m x 14 m= 149.8 m2

1610 ft2 x 3.58 ft x 7.48 gal/ft3= 43113.2 gal149.8 m2 x 1092 mm= 163581.6 L

60 ft18.3 m

57 ft 17.4 m

46 ft14 m

22 ft6.7 m

catchment area1320 ft2 + 1610 ft2 = 2930 ft2122.6 m2 + 149.8 m2 = 272.4 m2

Volume from Runoff35347.49 gal + 43113.2 gal = 78460.7 gal133879.2 l + 163581.6 l= 297460.8 l

Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient

catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal)

60 ft18.3 m

57 ft 17.4 m

46 ft14 m

22 ft6.7 m

297460.8 l x .9 = 267714.7 l

Sample runoff coefficientMetal roofs lose 5% thus coefficient 95%Concrete & Asphalt 90%Built up tar and gravel roofs 80-85%Clay tile roof??

78460.7 gal x .9= 70614.63 gal

60 ft18 m

22 ft6.6 m

35 ft 10.5 m

46 ft13.8 m

60 ft18 m

57 ft 17.1 m

46 ft13.8 m

22 ft6.6 m

3-5 ft or 1-1.5 m

1-3 ft or .3- 1 m

Calculating water holding capacity of the swaleArea = ½ x width x depth (formula for a triangle)

Volume of Water Holding Capacity= Area x length Volume = ½ x width x depth x length

width-= 5 ft or 1.5 m

Depth = 3 ft or .9 m

Length= 90 ft or 30 m

Calculating water holding capacity of the swaleVolume = ½ x width x depth x length

.5 x 5ft x 3ft x 90ft = 675 ft3675 ft 3 x 7.48 gal/ft3 = 5,049 gal.5 x 1.5m x .9m x 30m = 20.25 m3

20.25 m3 x 1,000 liters/m= 20,250 l

width-= 5 ft or 1.5 m

Depth = 3 ft or .9 m

Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient

catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal)

60 ft18 m

57 ft 17.1 m

46 ft13.8 m

22 ft6.6 m

Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient

catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal)

60 ft18 m

57 ft 17.1 m

46 ft13.8 m

22 ft6.6 m

Volume from Runoff1320 ft2 x .083 ft x 7.48 gal/ft3= 819.5 gal1610 ft2 x .083 ft x 7.48 gal/ft3= 999.55 gal

Total=1819.05 gal

Walmart parking Lot -17 acresRunoff?

Walmart parking Lot -17 acresRunoff=16,370,116 x .083 ft x 7.48=10,163,222.8 gal

Corn and Soy-23,500,000 acresState of Iowa- 35,922,000 acresRunoff=168,885,558,744 x .083 ft x 7.48=126,323,979,405 gal

Corn and Soy-23,500,000 acresState of Iowa- 35,922,000 acresRunoff=168,885,558,744 x .083 ft x 7.48=104,850,910,290 gal X .65=68,153,091,688104,850,910,290 gal X .2=136,306,183,377136,306,183,377-68,153,091,688=68153091689 gal

Brad Lancaster’s Principles of Rain water harvesting with Earthworks

• 1. Begin with long and thoughtful observation.Use all your senses to see where the water flows and how. What is working, what is not? Build on what works

• .2. Start at the top (highpoint) of your watershed and work your way down.Water travels downhill, so collect water at your high points for more immediate infiltration and easy gravity-fed distribution. Start at the top where there is less volume and velocity of water.

• 3. Start small and simple. Work at the human scale so you can build and repair everything. Many small strategies are far more effective than one big one when you are trying to infiltrate water into the soil

• .4. Slow, spread, and infiltrate the flow of water. Rather than having water run erosively off the land’s surface, encourage it to stick around, “walk” around, and infiltrate into the soil. Slow it, spread it, sink it

• .5. Always plan an overflow route, and manage that overflow as a resource.Always have an overflow route for the water in times of extra heavy rains, and where possible, use the overflow as a resource

• .6. Maximize living and organic groundcover.Create a living sponge so the harvested water is used to create more resources, while the soil’s ability to infiltrate and hold water steadily improves.7. Maximize beneficial relationships and efficiency by “stacking functions.”Get your water harvesting strategies to do more than hold water. Berms can double as high-and-dry raised paths. Plantings can be placed to cool buildings in summer. Vegetation can be selected to provide food.8. Continually reassess your system: the “feedback loop.”Observe how your work affects the site, beginning again with the first principle. Make any needed changes, using the principles to guide you.