California; Managing Rainwater - Sierra Watershed, Coastal San Luis Resource Conservation District
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Transcript of California; Managing Rainwater - Sierra Watershed, Coastal San Luis Resource Conservation District
Managing Rainwater
Regina Hirsch
Sierra Watershed ProgressiveSierra Watershed Progressive
Why?Why?
Why Manage Rainfall?Why Manage Rainfall? Slow erosion
Reduce mud areas
Water livestock
Irrigate pasture
Provide supplemental water supply
Decrease nuisance pests from unwanted pooling or flooding
When water speeds up
Why manage rainfall?•Enough rain falls in the United States each year to cover our country to a depth of 30 inches.
•How much falls in your watershed? On your ranch? In your yard?
•San Luis Obispo receives 27 billion gallons per year, on average
•27,154 gallons per acre per one inch rain storm
How fast does water move?How fast does water move?
Residence Time (USGS)
Antartica 20,000 years
Oceans 3,200 years
Glaciers 100 years
Groundwater Shallow: 200 years
Groundwater Deep: 10,000 years
k Lakes 100 years
Rivers 2 to 6 years
Why manage rainfall?Thirty percent of all runoff has turned to flooding or erosion problems due directly to our changes in the watershed infiltration dynamicchanges in the watershed infiltration dynamic.
How?How?
How best to manage runoff?How best to manage runoff?
Catch it first! Slow it move it store itCatch it first! Slow it, move it, store it
Rainwater tank catchmentRainwater tank catchmentTank catchment requirements:
•Cover•Cover
•Coarse debris filter
•Overflow
•Drain
•Manhole access
•Sanitary extraction
•First flush (where/when appropriate)
•Backflow or check valve
Rainwater Tank StorageRainwater Tank StorageAdvantages Disadvantagesg Disadvantages
Cleanest supply of water Readily available where needed
Tank storage can be cost prohibitive
Soft water Owner-operated and managed Promotes self-sufficiency
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Stored water is heavy, local codes may vary on
i i /f d ti dPromotes self sufficiency Conserves other water resources Low running costs
Fl ibl h l i
seismic/foundation needs
Leakage on steep slopes can cause undercutting of footing
Flexible technologies Safe for human potable use if treated Reduces erosion, flooding, and other
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Can be unsafe for small children if installed i lstormwater runoff effects improperly
How Big a Tank?gHow much water do you need in rainfall months? In dry months? Total? Annual Water Need?
Gallons/week350
How much rainfall do you receive in a drought year?
Annual Rainfall?Inches/year
18
Rainfall intensity? 1 05How much rainfall do you receive in an hour?
How many months does it go without raining?
Rainfall intensity?Inches/hour
1.05
Dry weeks? 14ow a y o t s oes t go w t out a g?
How big is the surface you are catching off of?Size of harvesting surface? Sq/ft
1000
What is the roof and gutters made out of? Surface permeability? 90%
SURFACE POTENTIAL: Surface area (800) x .623 x Annual rainfall (18) x Perm. (90%) = 10,092 gallons
STORAGE NEED: Need (350) x Dry weeks (14) =4900 gallons
T k C id tiTank Considerations•Not opaque
•Lighter color keeps water cooler
•Potable plastic if for quality drinking water
•Non-galvanized if used for irrigation (or use liner)
•Underground tanks should have swivel unions and flexible lineswivel unions and flexible line
•Covered, but accessible
•Seismic requirements for larger tanks especially verticaltanks, especially vertical
Other Other tank options
T k D d D ’Tank Dos and Don’ts
Do: Don’t: Use a vertical tank on the highest point possible. This gives
options to distribute via internal tank pressure.
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Never use sand as a base for tanks. Shifting and erosion can undermind footing and Low pressure valves can work off as little as 7 psi. Use
0.433 psi gain per foot of elevation from water holding surface.
Bring water in ‘quietly’ to let fines settle and stay below
can undermind footing and cause tanks to shift and move.
Never leave a tank empty in a freezing climate.
Bring water in quietly to let fines settle and stay below extraction zone.
Always leave room for expansion of joints and use appropriate bulkhead materials.pp p
For best water quality, use a floating extraction hose set for the upper ¾ of the tank, but not from the top.
For long term storage, leave 1/6 of your tank unfilled to g g , ykeep water aerated.
Post all plumbing with “rainwater, non-potable”
First Flush, Filters, and Siphonspto have or not to have?
Topographical Rainwater Catchment•Best suited for decreasing Best suited for decreasing stormwater runoff
•Increasing groundwater and interflow water quantitiesq
•Best done on slopes less than 5%
•Basins are filled with mulch and planted to filter and slow water
SLOW it DOWN, SOAK it UPBerms and swales on contour slow surface runoff. Planting these basins will aid in soaking up extra water inflitration.
Basins are planted with appropriate trees that can provide needed shade cover for livestock and soilBasins are planted with appropriate trees that can provide needed shade cover for livestock and soil.
SLOW it DOWN, SOAK it UP
SLOW it DOWN, SOAK it UP
Tools and ResourcesTools and Resources
ToolsLevel (water level)
A frame or survey stadia rod and scope
Measuring tape
ResourcesResourcesCost Effective Tank Shoppingpp g
Local Community Services Districts
Watershed Groupsp Ebay General Contractors Car Washes
Water Information Resources
Car Washes
ARCSA www.arcsa.orgARCSA www.arcsa.org SLO Green Build SLORCD
d Texas A&M Rainwater Guide Harvesting Rainwater, Brad Lancaster
Site DesignSite DesignCHECKLIST
•Solar and wind aspect
•Existing tree and shrub community
•Rough topography map
•Neighboring waterways
S il i i•Soil composition
•Percolation rate
•Drainage plot
R i t k h t•Rainwater worksheet
•User needs and accessibility
•Other resource inventory
“As soon as you start doing, you learn how to proceed.”B Mollison-B. Mollison