Precipitation

From Water Wiki

Like all southeastern states in the United States, North Carolina gets a lot of precipitation relative to other places on Earth.

Even in the worst drought year of record, 2007, every place in North Carolina got at least 34" of precipitation, or more than much of the western United States gets in a normal year.

The grim reality that 34" of rain puts much of North Carolina in an exceptional drought, while it makes for a normal year in much of the rest of the country, can be attributed to several factors: 1) the inefficiency of North Carolina in using water; 2) the lack of multi-year storage (unlike many western states); 3) operational decisions at the reservoirs and timing issues in the precipitation; and 4) intra-state variations.

On the last note, there are important differences in average precipitation across the state. 

Fascinating research out of Florida is demonstrating that urbanization and drainage have direct, local effects on precipitation. As we increase impervious surface, reduce infiltration to the surficial aquifer, and remove wetlands, we reduce regional evaporation and (surprisingly to many) regional precipitation. Is this happening in the piedmont of the southeastern United States?

Many people wonder about the effects of climate change on precipitation in the southeast. At present, the studies do not clearly predict either an increase or a decrease in North Carolina precipitation as the world heats up. Regional models predict a drier climate to the south (Florida and south) and a wetter climate to the north, but are unclear on the predicted trends in North Carolina. There is, however, a widespread belief among those who study climate change that the precipitation that occurs will happen in more intense events spaced over more time, with dry periods between. This increased variability, or "flashiness", is itself a problem to be dealt with by water allocation policy.

Drought

Although North Carolina has had abundant precipitation in the last century, the longer record--paleoclimatic data--suggests that extended periods of drought are not unusual. One historically interesting research effort, using tree ring data, documented droughts that may have doomed The Lost Colony on North Carolina's Roanoke Island (1587-1589), as well as causing the very high mortality in the first years of the Jamestown settlement. "Only 38 of the original 104 colonists survived the first year (1607) at Jamestown and of the 6000 people that came to the settlement between the years of 1608-1624, only 3400 survived. Most reportedly died of malnutrition."^[1]

For an excellent website on drought in North America from a long-term perspective, see the research site of the Lamont-Doherty Earth Observatory at Columbia University.

Notes

1. ↑ Stahle, David W., Cleaveland, Malcolm K., Blanton, Dennis B., Therrell, Matthew D., and Gay, David A. Jamestown/Roanoke Drought Index Reconstruction and Description from the WDC Paleoclimatology archive. (Nottoway River Baldcypress Ringwidth, Earlywood, and Latewood Data) Blackwater River Baldcypress Ringwidth Data from the WDC Paleoclimatology archive. See http://www.ncdc.noaa.gov/paleo/drought/drght_james.html