According to the Drought Monitor, drought conditions worsened slightly across the entire US compared to three weeks ago. As of September 17, 2013, 48.2% of the contiguous US is experiencing moderate or worse drought (D1-D4), as the early 2010s drought continues month after month. This value is about 11 percentage points lower than it was in the early spring. The percentage area experiencing extreme to exceptional drought decreased from 14.8% last month to 6.9% last week! This is more than 10% lower than it was six months ago. The eastern third of the US was wetter than normal during August, which helped keep drought at bay. The east coast in particular was much wetter than normal and the summer monsoon was much more active this summer compared to 2012, assisted by a persistent upper level blocking pattern. Instead of Exceptional drought in the West like there was earlier this summer, record rains and flash flooding was the story in September. While this record-breaking series of events broke the drought in some areas of the West, long-term drought continues to exert its hold over the region. Compared to earlier this summer, drought increased in area and intensity across the Midwest.
Figure 1 – US Drought Monitor map of drought conditions as of September 17th.
If we compare this week’s maps with previous dates (here and here, for example), we can see recent shifts in drought categories. Compared to mid-August and early September, and despite recent rain events, drought expanded or worsened in the Midwest (Iowa, Missouri, Illinois, Minnesota, and the Dakotas) as well as Louisiana, Arkansas, and Mississippi. On the other hand, alleviation is evident in small places in the West, as the following map shows.
Figure 2 – US Drought Monitor map of drought conditions in Western US as of September 17th.
After worsening during late winter into spring 2013, drought conditions steadied in late summer. The differences between this map and early September’s is the reduction in area and severity of drought, especially in the southern half of the West. The area experiencing Exceptional drought decreased significantly over the West and the percent area with no drought increased. Figure 2 also shows that the percent area with no drought is still lower since the start of the calendar year (24% to 18%).
Here are the current conditions for Colorado:
Figure 3 – US Drought Monitor map of drought conditions in Colorado as of September 17th.
There is evidence of substantial improvement in Colorado since just a few weeks ago and certainly compared to earlier this year, when drought conditions were their worst. Compared to the start of the calendar year or even three months ago, the percent area of every drought category decreased significantly. Only 1.5% of the state currently has Exceptional drought. Only 84% of the state is even experiencing any drought condition today, a far cry from the 100% that lasted for well over one year. The links in the first paragraph dealing with last week’s rains combine with this graphic to demonstrate that places that receive one year’s worth of precipitation in one week’s time bust their drought! Many communities would trade those record rains for a little bit of drought, given the extensive damage to infrastructure and the eight people who, as of this morning, perished in the severe weather event.
Let’s compare Figure 3 to similar Colorado maps from earlier in the year. First, this is what conditions looked like just two weeks ago:
Figure 4 – US Drought Monitor map of drought conditions in Colorado as of September 3rd.
The over-active monsoon season helped reduce drought severity from Denver northwest toward the Wyoming border. I said at the time I hoped that trend continued, but I could never imagine what would happen in the interim.
Here is a look at some of the worst drought conditions Colorado experienced in the past year, from late April 2013:
Figure 5 – US Drought Monitor map of drought conditions in Colorado as of April 25th.
Conditions were horrible earlier this year. Reservoir levels declined and crops failed as a result of the higher than normal temperatures and much lower than normal precipitation. I certainly don’t want to see additional flooding, but I would like to see normal precipitation return to the state and the region.
Figure 6 – US Drought Monitor map of drought conditions in the Midwest as of September 17th.
Drought expanded in the Midwest in the past two weeks: the percent area with no drought decreased significantly from 48% to 43%. Three months ago, the value was 93%. This region collected rainfall this month, but the amounts continued to track below average.
Figure 7 – US Drought Monitor map of drought conditions in the South as of September 17th.
Compared to early summer, drought as a whole expanded across the South in 2013. Instead of 44% area with no drought three months ago, there is only 16% today.
US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions than the global warming observed to date. Different natural oscillation phases preferentially condition environments for drought. Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance. Beyond that, drought controls remain a significant unknown. Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past. Without comprehensive planning, dwindling fresh water supplies will threaten millions of people. That very circumstance is already occurring in western Texas where town wells are going dry. An important factor in those cases is energy companies’ use of well water for natural gas drilling. This presents a dilemma more of us will face in the future: do we want cheap energy or cheap water? In the 21st century, we will not have both options available at the same time as happened in the 20th century. This presents a radical departure from the past.
As drought affects regions differentially, our policy responses vary. A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts. The last thing they want is their reliability to suffer. Americans are privileged in that clean, fresh water flows every time they turn on their tap. Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as found this year). Power utilities continue to provide hydroelectric-generated energy.
That last point will change in a warming and drying future. Regulations that limit the temperature of water discharged by power plants exist. Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago. Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce. Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures. As with other facets of climate change, technological innovation can help increase plant efficiency. I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.