Water is our most basic need, and our most important resource. Most environmentalists would agree that water conservation should be a top priority, but most people don’t know about the full array of water conservation strategies that are available. If we think of water as a metaphor for money, we can talk about various water-saving options as different types of bank accounts.
Everyone knows about collecting rainwater from your roof into a tank. Water can be collected from any clean surface into a plastic, concrete or metal container. The container could be a stock tank, a food-grade plastic barrel, or a 5,000 gallon catchment tank. This is a great option for having water immediately available when you need it during the dry season. However, a tank will only cover a small percentage of your water needs. The University of California recommends an average application of 0.623 gallons per square foot, per week during the dry months of May to October. So my 1200 square foot garden space would require 747 gallons per week. With a 25,000 gallon catchment tank installation, careful water use could make this water last through the dry season. But we’re only talking about my annual garden. What about my orchards and other perennials? My livestock? My pastures? All these things need water during the months when none will fall.
Our tarped vegetable garden collected 550 gallons of clean water from the winter rains.
These 18″ paths collected 50 gallons per 1 inch of water, per 100 foot row.
If water is money, man-made tanks can be thought of as your wallet. That pocket money is readily available for immediate use, but you can’t carry a lot of it with you, so you end up spending it quickly. To pay your regular bills, you’ll need a checking account. This is a vessel for containing much more water than a tank can hold, while still keeping the water available for regular use.
Healthy soil acts like a sponge, soaking up water during rain events and redistributing it to vegetation later. According to the USDA, a 1% increase in soil organic matter can increase the soil’s water holding capacity by 25,000 gallons per acre. My 2-acre pasture could hold at least twice as much water as my holding tanks after every rain event. Let’s say my pasture soil is about 2% organic matter at this time. After a few years of managed grazing, it could rise to 5% organic matter, or an increase of 75,000 gallons of water holding capacity per acre. This water is held and distributed to my pasture grasses over the dry period, allowing it to stay green longer, and provide more food for my livestock.
The 4 S’s
|
Source: Sonoma County Resource Conservation District
We have a free water collection container that nature has provided, called an underground aquifer. This is our long term savings account. Anyone who manages property, no matter how small, can contribute to filling the aquifer, through rain gardens and other recharge basins. When we direct rainwater to a recharge basin, rather than a sewer system, we are making a deposit into our water bank. Water that flows away into sewers, drainage ditches, and eventually the ocean, is lost from the water cycle forever. Water that percolates down into the aquifer is available for us to use again and again.
A recharge basin can be as small as a 2’x4’x6’ rain garden, filled with rocks, and built to accommodate the runoff from your suburban driveway. It can be as large as a stock pond and accommodate fish and aquatic plants. The most important feature of a recharge basin is that it has an unlined bottom, so water can seep into the soil.
In Rainwater Harvesting for Drylands and Beyond, Brad Lancaster describes different types of earthworks that can be used to direct rainwater into our aquifers. The most common of these is a pair of structures often used together: berms and swales. A berm is a raised earthwork that slows the flow of water down a slope and is usually built “on-contour.” The corresponding swale is a low point, from which the soil for the berm is often dug, and is designed to hold and sink the water stopped by the berm. A berm can be as small as a few inches of soil hoed up in a row, or as large as a 6’ embankment.
Image source: https://santacruzpermaculture.com/2019/08/berms-swales/
We can all contribute to filling our community’s hydrologic bank account, as well as collecting from rain events for immediate use. Applications for storage of rainwater are only limited by our ingenuity.