STREAMFLOWS
The U.S. Geological Survey maintains a real-time stream gauging network that monitors flows in all major river basins in Kentucky. Measurements of streamflow are a very good indicator of the longer-term hydrologic impacts of drought. During the developing stages of drought, streamflows provide valuable information on the severity and regional extent of emerging problems. Streamflow data is evaluated relative to the long-term record to determine drought intensity and identify potential problems associated with water shortages. Once a drought has matured, streamflow measurements are critical at many locations where water withdrawals have the potential to cause adverse environmental impacts to streams.
Weekly and Monthly Streamflow
For a slightly longer-term perspective of streamflow conditions across Kentucky, the U.S. Geological Survey computes average flows for the previous seven, 14 and 28 days. The resulting average streamflow values are categorized relative to the long-term record and assigned levels of severity based on the frequency that similar magnitudes of low-flow have occurred in the past. By averaging over a period of several days to several weeks, the values on the map are more indicative of longer-term conditions than daily average or real-time streamflow measurements.
Seven-Day Average Streamflow 14-Day Average Streamflow 28-Day Average Streamflow
Lakes and Reservoirs
U.S. Army Corps of Engineers Projects
Another useful measure of the impact that drought is having on a region is the status of area lakes and reservoirs. The Division of Water monitors data from 12 projects operated by the U.S. Army Corps of Engineers (USACE) from three USACE districts:
Louisville,
Huntington and
Nashville. These projects strive to maintain reservoirs at pool levels consistent with the operating guidelines as part of the larger mission of flood control and navigation in the Ohio and Mississippi rivers. Beginning in April, the releases from the reservoirs are managed to allow filling to the “normal summer pool elevation.” Similarly, between the months of September and November most projects begin releases to bring down surface elevation to “winter pool.” This process generally creates a large increase in streamflow when it may be needed the most. Significant precipitation deficits in the basin above the reservoir can adversely affect the attainment of normal summer pool elevation and the volume of water released during winter draw-down. This, in turn, may result in low flows in the river below the project when releases from the reservoir are reduced to the minimum needed for water quality and aquatic habitat.
By examining the data for “current pool elevation” and “current outflow,” valuable information about the status of large headwater areas above the USACE reservoirs can be obtained.
Updated Aug. 13, 2008
U.S. Army Corps of Engineer Reservoir Information
Updated Aug. 13, 2008
Currently, all reservoir levels have been reduced through draw-down to winter pool elevation though recent precipitation events have temporarily increased most. Rough River Lake was dropped to winter pool elevation in September to allow for repairs to the stilling basin.
Small Lakes and Water Supply Reservoirs
The Division of Water will monitor selected small water supply reservoirs when conditions indicate that water supplies may be threatened by persistent drought. Most small water-supply lakes have been returned to near-normal elevations, but a few still remain well below-normal due to localized precipitation deficits. As a result, there are some communities that remain on advisory.
