The D-Word Returns
Posted August 24, 2009
Unfortunately, the "d" in this case being drought, as a small portion of North Carolina that includes parts of our viewing area has slipped back into a moderate drought designation in the latest update of the U.S. drought monitor. You can see (image 1) the affected region marked with the tan color just west of Wake County and covering parts of Lee, Durham, Orange and Chatham counties in our viewing area, along with a couple of others just to the west. So far this is considered a "hydrological" drought based on rainfall amounts, stream flows and groundwater levels, with relatively little agricultural impact. It is worth noting, though, that most of our area is still shown as "abnormally dry," a step away from the first drought category.
We can scan a few other maps and graphs for a brief sampling of some of the factors influencing the drought designation and illustrating a few of the impacts. For example, a map showing "percent of normal" rainfall estimates over the past 60 days (image 2) based on a combination of radar data and gage readings shows some substantial areas with only 25-50% of normal rain over that two months stretching north and west from the Triangle, with a larger area in the same region enclosed in a 50-75% contour. Rainfall amounts have been more mixed and closer to normal across many other parts of the region.
The fairly dry conditions have lowered groundwater levels a little at a monitoring well in Chapel Hill, as shown by the graphs in images 3 and 4, which show that the level remains somewhat below the long-term median, but still doing a little better in historical terms than it was this time last year. In addition, there have been some notably reduced stream flows through the region, leading to lake levels at Falls and Jordan lakes that have fallen noticeably below normal, by just over 2 feet at both lakes, after having run at or above normal for much of the past year (images 5 and 6) after recovering from some very low levels late last summer.
If there is any good news to be had in the information that's out there right now, it is a seasonal drought outlook (image 7) that was issued just a couple of days after the drought monitor map. The outlook specifically addresses the small moderate drought area over our state and places it in the green "improvement" category, as the drought forecasters believe that outlooks over the short and medium term suggesting near normal to possibly above normal precipitation in the coming weeks and months will make the drought designation here fairly short-lived. We'll certainly hope that turns out to be the case...
You can access a lot of the infomation shown here through the N.C. Drought Management Advisory Council web site. I've included a link with this post.