When you understand how water cycles through your landscape, you can find the “wasted energy” and catch and store it better. You can direct it to places that can use it and direct it away from places that don’t need it. That is the essence of water design in permaculture.
Healthy natural systems tend to store water high on the land, slow, spread, and sink it into underground aquifers or to be stored in the soil. They do this with tree cover, natural treefall barriers, beaver dams, deep rooted, sponge like tall grass prairies, and in other ways.
The relationship between the natural world and water is symbiotic and regenerative. Complex living systems use water multiple times, benefiting many living things, before it returns to the clouds through evaporation. As we’ve seen, tree systems create rain and bring water back to repeat the process.
Usually, the best place to store water is in the landscape and soil. A tremendous amount of water can be stored in the soil, far more than is practical to store in tanks. This approach can also help prevent flooding.
Native tallgrass prairie species can absorb 9 inches of rainfall per hour before any kind of runoff occurs, and one acre of established prairie will intercept as much as 53 tons of water during a one-inch per hour rain event.
Forests filter and regulate the flow of water, in large part due to their leafy canopy that intercepts rainfall, slowing its fall to the ground and the forest floor, which acts like an enormous sponge, which can absorb up to 18 inches of precipitation depending on soil composition before gradually releasing it to natural channels and recharging ground water.
In a North Carolina Watershed study (Kays, 1980) the mean soil infiltration rate went from 12.4 in/hr to 4.4 in/hr when a site was converted from forest (layer of decomposing biomass on soils) to suburban turf. Other studies (Bharati et al. 2002) have found similar results when comparing hourly infiltration rates and soil bulk density of forested areas with crops and grazed pasture.
With good design, your system will continue to store water in the soil on its own, once the system is established.
In Florida, with our ultra sandy soils and intense drainage, high water tables and flooding, we need to move water away from our land sometimes. There is a time to store it, and a time to direct it away from your land, if there is too much of it. Both are important skill sets to have.
In most cases, you do want to:
- Slow it
- Spread it
- Sink it
- Store it as high on the land as you can
Hands On Activity
If you’re in hurricane country, look up your evacuation category. Do a search of your county name + “evacuation zone” and you should find a map or database that you can enter your address into. Even if you’re inland, do this exercise. Note what category of storm would cause you to need to evacuate to be safe from storm surge (if any).
Do a search in FEMA’s flood map database for your site. Enter your address or find the site on the map. Note if you are in a flood zone or not, and what type it is.
Observe and record where water flows and where it collects on your land. Think about how you can use that energy in your design. How can you place elements where they can benefit from water? How can you direct water to where it is needed most? How and where can you store it?