Norfork Microclimate Pilot Study, Phase 2
Jessica P. and Sarah R.

6th Grade Science students
Norfork Elementary School


In the original study by Rick H. and others conducted last year (2002-03), it was determined that our microclimate differed between upland areas and river valley sites. This difference was most obvious during hours of darkness and it varied depending upon the seasons. Our problem is to try and identify what causes these differences and determine what is the effect of water releases from area dams upon the bottomland climate. From the earlier work, our hypothesis is that any effect will vary upon the timing and amount of water released at the dams. Cold water released at night should really cool down the observed air temperature, otherwise little climate difference will be measured between both datalogger sites.

To see if we were correct, we made a record of water releases from each dam. We did this by downloading the hourly text data from a web site published by the US Army Corps of Engineers on water released from their dams. We copied each school days data to an Excel spreadsheet. At the end of the month we deleted the columns of data we didn't need and left the date, time, and the cubic feet per second of water released. Since it takes about two hours for water released from Norfork Dam to reach the White River where our datalogger site is, we shifted the last column of numbers down two hours so it represented when that water would start affecting our river bottom climate. We did the same for the water released from Bull Shoals Dam on the White River, except it takes about twelve hours for that water to reach our site. Then we printed a copy of all the data for that month.

Our next problem was to compare the GLOBE graphs of air temperatures recorded at both sites with our water release data (See Figure 1 below). The GLOBE graphs were made using Universal Time (UT) and our river data was made using Central Daylight Time (CDT). Since we are interested in the times that we can measure a large difference in temperatures, we mainly wanted night time periods. At this time of year (October) dusk is at about 2400 UT and dawn at about 1300 hours (UT) daily. Thus, we highlighted those times on our printout for closer study. October 2003 (Editorial Note: This hand drawn conversion method was easier for young students to understand and relate to others than conversion of all times to UT so that an analysis could be made. Both methods should accomplish the same goal.)

Figure 1 - GLOBE diurnal graph of data recorded at upland (red) and bottomland (green) sites for October 2003.

We discovered that this graph was typical of October graphs where such data was available. The seasons are changing and on most nights little difference in temperature was observed. However, toward the latter part of the month many nights reflected a large difference in temperatures between the two locations. It is for these dates that we directed our attention to try to find out why the river bottom experienced such lower temperatures. On 19-25 October 2003, water releases from Norfork Dam seem to match the reduced temperatures observed in the river bottom. During the 10-19 October 2003 period, water releases ended before dusk and little difference in temperature was recorded. Thus, the data suggest that our hypothesis is correct.

What could explain the higher bottomland temperatures on 26 October 2003? Abnormally large releases of water from Bull Shoals Dam on 24-25 October 2003 seem to be a possible cause if the warmer river valley temperatures recorded. Water temperature records relate that river water was about 13 degrees Celsius with air temperatures at the upland site about 8 degrees Celsius. The large amount of warmer river water could explain this unusual recording. Such was experienced often during the winter months of 2002-2003 and the water releases from the dams were suspected to cause this to happen. These data seem to confirm this case. Thus, our hypothesis should be changed to reflect warmer bottomland microclimates during periods of large water releases when the air temperatures are low.

To confirm our study results, we should continue to compare recorded values, especially at colder periods during the winter.

Last Updated 27 Nov 2003