Good rain, but some drought continues
Posted October 19, 2011
Areas of rain that crossed our region last night produced some substantial amounts, anywhere from a few tenths to well over an inch, and we may add another few hundredths to several tenths today on more of a hit and miss basis. Periods of rain like this in recent months make it seem as if drought shouldn't be an issue at all, but the latest drought advisory map (shown here as the first image) show that western and southern parts of our viewing area remain in moderate drought status, including all of Durham and Orange counties, Cumberland county and the southwest third or so of Wake County. While notable rain has occurred at times recently, it hasn't been really consistent or evenly distributed, especially toward the upper portions of the Neuse and Cape Fear river basins.
We have had enough precipitation over most of NC to keep topsoil moist (see the second map showing near normal crop moisture for our state) and vegetation green, which adds to the sense that drought ought to be a distant memory. However, there are some indicators related to longer-term rainfall deficits that illustrate the reason some of us continue with a drought designation. For example, a look at the groundwater graph from Chapel Hill in the third image shows that the groundwater level there (red line) remains over 3.5 feet below the long-term median (black triangles) and toward the lower end of the lowest 10% of historical readings for October. Likewise, if you've had a look at Falls Lake lately, you'll note its level is around 4 feet below normal, as seen in the fourth image showing the lake level over the past six months. The green line on that chart is the normal, or guide curve, level.
The rain that fell last night should keep soil well-moistened for the time being, and give a brief bump to streamflows and perhaps lake levels in the next few days, but it seems unlikely to change our drought designations much, since we appear to be headed for a dry stretch starting tonight and lasting the next 6 or 8 days.