Total annual precipitation refers to the amount of water that fell from the sky in the last year. This includes rain and the water in snow, sleet, and hail. Precipitation plays an important role in plant survival, fire risk, insect outbreaks, and river levels.
For the Forest Health Index, we use the average amount of precipitation across the watershed. This approach gives a better sense of what is happening across the forested region as a whole, rather than looking at data from a single location.
Moderately low: Annual precipitation was lower than average, although similarly dry years have occasionally occurred within the climate record for this watershed. During dry years, some trees may be stressed by low water availability, putting them at greater risk than usual for attack by disease or insects, and fire risk may also be increased.
In the semi-arid state of Colorado, precipitation is a critical component of our hydrology (or water system). Together, precipitation and air temperature have the largest influence on the amount of water available to forests. Dry years place stress on plants and animals within forests. They also mean that less water is available for human needs. Wetter years, by contrast, allow for ample water supplies but increase the danger of flooding and may leave some species of trees more vulnerable to infection.
The above graph shows that precipitation varies widely from year to year. Over the last few decades, there is no trend of yearly precipitation continuing to either steadily increase or decrease over time. Likewise, climate change projections for Colorado do not show our state consistently having wetter or drier years in the future. However, climate change may impact our water availability in other ways. For example, what time of year heavy storms occur may differ from typical patterns of the past, and as average air temperatures continue to rise, it is likely that we will see a shift in how water is delivered—with rain replacing snow at certain times of the year. Although we do not have much control over how much precipitation falls in a given year, we can help conserve resources during dry years by reducing water consumption in our homes and lives.