The Seven Tenets #4: Manage Water Wisely
In the Desert Southwest, wise water management is a given, but it is also important in places where there is, or has always been, abundant water. A year of drought in these places can be devastating because people are generally unprepared. So, it is best to be ready when a crisis strikes and manage this precious resource. Wise water management does require some pre-planning and creative design work to create infrastructure that puts the water where it can be useful instead of just running off to the street, or watershed, eroding the land and picking up pollution as it moves downward.
For an outstanding resource on Water management, check out the Brad Lancaster’s web page and award-winning book series “Rainwater Harvesting for Drylands and Beyond.” In his lectures, Brad tells us that, in Tucson, AZ where he lives, more rainwater falls in one year on the surface area of the city than the entire city consumes from the municipal water supply. The problem is that in most urban environments, the strategy for managing water is to move it quickly out of the landscape and into storm drains and culverts. Over time, the landscape begins to suffer from this loss of water, creating a progressive decline in soil health, which in turn reduces the landscape’s ability to absorb water. As this happens, the speed and violence with which runoff accumulates and surges away from the landscape increases, creating an ever more challenging and expensive water management situation. As Brad likes to say, “our drainage infrastructure gets rid of our free water.”
The critical components of wise water management include contouring the landscape to take advantage of the movement of water based on slope and directing it to plants and trees. Here are some great strategies that we use on the farm and that you can use to improve your gardens and landscapes:
Mulching is an essential way to prevent evaporation and water loss between rain events, especially here in the desert. As a bonus, mulch encourages biological activity in the soil and moderates soil temperature, which is important for healthy plants. On the farm, we used drip irrigation on our raised tomato beds and mulched with plastic to hold in the moisture. Tomatoes require even moisture and mulching is the single best way to achieve this balance. If you obey your sense of place and look for mulching materials that are available to you, it will require a lot less effort and money. At home, I try to use what is plentiful, including fallen leaves and pine needles. I grow cover crops to create extra plant material that I can mow and use for mulch.
Obey micro-climates, which are created by various structures in the landscape. Shade, fences, walls, trees, and sheltered courtyards are good examples. If you live in a wet climate and have a plant that does not tolerate soggy soil, pick a south facing location on a slight slope to ensure the soil drains and dries more quickly. Here in the Desert Southwest, I use partial shading over my tomato plants, which creates a cooler microclimate around the plants on the hottest days, sometimes as much as 10 degrees cooler. In turn, there is less evapotranspiration from the plants leaves and the surrounding soil, reducing our water use. The plants pollinate and set fruit better under the shade cloth when the ambient temps are inhospitable.
Use native and water wise plants Looking back at Sense of Place, using native and water wise plants is another great way to manage water. These plants require a lot less effort and cost a lot less over the long term in terms of water. They are easier to establish and perform much better over the long term with less input and labor.
Create humus! Good soil tilth will give your soil moisture holding capacity. We build our soils with cover crops and manures, which add organic matter to the soil and in turn humus. Add as much compost as possible to your soil in the spring and fall. Over time you will begin to see earth worms and the soil will take on a light crumbly texture with plenty of moisture holding capacity.
Contouring is a design concept aimed at capturing and storing rainwater rather than let it run off your property. It takes advantage of the land’s natural undulations and slopes and directs water where you want it. Good examples include creating a crescent shaped basin on the downhill side of a tree, or more simply capturing excess water from your roof using rain barrels and underground tanks and cisterns. Some communities are starting to allow “curb cuts” which directs some street run-off onto your property. For more information on contouring, check out Brad Lancaster’s book, referenced above.
