Soil Moisture

---

Soil moisture refers to how much water is being held in the ground at any given time. It is important in determining whether plants are able to grow, flower, and survive. It also plays a role in how much water reaches streams and rivers during rain storms or spring snow melt.

For the Forest Health Index, we use soil moisture data from GRACE, a NASA satellite that uses changes in gravity to measure water on Earth’s surface and in the ground. It operates at a broad scale, grouping together moisture from 16 mile (or more) areas. It can provide a good general sense of whether a summer is wetter or drier than the year before and reveal when soil is drying from month to month.