Terraces and swales for water storage and soil protection
For agricultural land, it is vital to protect the soil so the volume increases and the quality improves each year. On sloping land design and build systems to protect your soil, such as swales, terraces and tree terraces. Choose the method and design that best suit your needs and situation.
For most farmers, large crops are dependent on rains. Therefore, most of the vegetable and grain crops are only grown in the wet season. There are techniques that can make the wet season crops more consistent with higher yields, and sometimes enable dry season crops to be grown where they previously were not.
All farmers can store and retain the water in the soil. Mulch keeps the water in the soil, stopping the soil from drying up. Healthy, living soil is also important for water storage because it holds at least 50% more water than unhealthy soil. This reduces water use in the dry season, sometimes by more than 50%!
For mountains and sloped land, swales and tree terraces catch and store water. Even gently sloping land holds a lot more water if swales and tree terraces are used. Rainwater enters the soil and increases underground water storage, which feeds natural springs and underground water supplies. Read Permaculture design strategies and techniques (Ch 3) for how to make and use tree terraces and swales.
When you have a good swale or terrace system in place it controls where the water from rain and irrigation goes:
- The system catches, spreads and stores water in the ground where you want it. For most types of rain this means all of the water. The soil just below each swale or tree terrace is always the wettest.
- For heavier rain the system allow excess water to flow through and out of the system without causing erosion and damage, while still retaining and storing most of the water.
- For very heavy rain the swales allow the rain to flow out of the system where you want it to go without causing damage or flooding.
Read Chapter 13 Sustainable Agriculture for the process of making a tree terrace system.