Harvesting monsoon rain saves gardens

Climate change clearly has arrived in the American Southwest with scorching heat daily. And sadly, no monsoon rains yet, even though monsoon season officially started on June 15th. 

We all hope that storms will be sweeping in from the Gulf of Mexico and Sea of Cortes soon. That’s what the TV weather forecasters keep telling us nightly. So now is the time to prepare to capture that rain water. And by doing it now you will already be prepared to harvest rainfall again when winter storms arrive. (6 hours after I posted this a fierce monsoon storm struck Tucson. Maybe I should have posted it earlier.)

There are basically two methods to keep water in your garden for future use. One is to save it in above-ground or below-ground containers and the other is to help the rainfall percolate into the soil instead of running off your property and away from your plants.

Start with your flower beds

While most flower beds are mounded — hopefully because you add a thick layer of organic mulch twice a year — you may want to consider digging little basins in the center of the beds to capture as much rain as possible. Be careful not to damage the roots of your plants. The water will then seep into the earth for future use by the plants.

If you plant in raised boxes, be sure to have good drainage on the bottom or during a heavy downpour your planter may flood and drown the plants.

High priced infiltration or on the cheap

Infiltration, in its costly form, involves digging a large pit in your yard to hold rain runoff from your roof. This means rain gutters and downspouts must be installed. The pit must be lined with a strong, permeable material and must have an overflow to channel excess water away from your home. Water will seep from the pit into the surrounding soil, thus “irrigating from underground.” Consult a landscape architect or soils engineer if you plan to do this.

In the less expensive version of infiltration, dig or drill narrow, deep holes spaced apart in a circle around trees and shrubs. These holes will fill with rain which will then seep into the soil. To do this effectively, you may have to line the holes with strong, permeable material to prevent the sides from collapsing into the holes while allowing water to escape into the root zone. Some people recommend using French drains, those metal drain pipes with holes, installed vertically like mini-wells.

In the super-cheap version, very coarse gravel or small rocks may also keep the holes from collapsing. Deep watering like this will encourage trees and shrubs to grow deeper, stronger roots. And deeper roots mean more stability when the seasonal winds howl across the landscape in Spring and Fall.

Install cisterns or rain barrels

Our last suggestion is to add a cistern or rain barrel to capture rainfall which you can use later by pumping the water out for irrigation. Unlike infiltration which is designed to allow water to spread out underground during and after a storm, a cistern is supposed to hold water in the container, not diffuse it.

If you want to add an underground cistern–which is essentially a well filled with rainwater–you should consult with a landscape architect or soils engineer because there are engineering and permit issues involved. The sides and bottom must be sealed to prevent water from escaping and the system must have an overflow drain. If water overflows in the wrong direction you may have serious and potentially expensive erosion problems from damage to your home or your neighbor’s house!

On the other hand there is a simple way to capture rain: buy a big plastic barrel or one of the large above ground cisterns–prices start at about $70 and go up into the thousands depending upon the size. It can be a quick and easy method to store the rainfall from the downspouts on your roof to use later. The big risk here is that the rain falls so intensely that the barrel overflows and starts flooding the area before you notice it.

Are cisterns still illegal?

Happily and wisely, the laws in Colorado and Utah banning water harvesting have changed. Now Coloradans can have 2 rain barrels with a total capacity of 110 gallons of water for use on their own property. In Utah homeowners can save up to 2500 gallons of rainfall in above or below ground cisterns for use on the same property. In both these states, please check for specific regulations.

Many other states, including Texas, Nevada and California, now have laws supporting rainfall harvesting and rules regarding usage. These states now allow saving rainwater that falls on your roof and using it in your garden. Using the water for drinking water is banned in some states, discouraged in others. My advice: do not drink it. Give it to your garden.


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