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GIS Data for Pool 5 Drawdown Project

Background

The annual cycle of fluctuation in water levels has been modified on the Upper Mississippi River, primarily by the system of dams installed by the U.S. Army Corps of Engineers in the 1930s to enhance commercial navigation. The navigation pools that resulted from the artificially maintained high water levels were initially diverse in structure and supported a rich variety of fish and wildlife. Over time, the high water levels have contributed to a degradation in the habitat quality of these pools and large expanses of open water have developed that are less beneficial to fish and wildlife resources. In an effort to enhance the production of aquatic vegetation and improve fish and wildlife habitat, the U.S. Army Corp of Engineers conducted a water level reduction on Navigation Pool 5 in summer 2005 and has planned a second drawdown for summer 2006. The drawdowns target a reduction of water levels by 1.5 ft. at Lock and Dam 5 (L&D 5) during the growing season. The GIS data depicting substrate exposed with the 2005 drawdown, along with aerial photography, are served on this web page for use by resource managers and planners.

Status (2005)

The drawdown was initiated on June 13 and the target reduction of 1.5 ft. reached on July 1. The drawdown was maintained near the target level at L&D 5 until July 19, when low flow conditions (<24,000 cfs) necessitated switching from “secondary” to “primary” control of the pool surface water elevation.  Under “secondary control,” the pool elevation is maintained at the desired level at the dam and the pool upstream of the dam rises and falls with river discharge.  With the switch to primary control, a water surface elevation of 660.0 was maintained at the primary control point at River Mile 748.5 and this required the water level to be raised at L&D 5. Subsequently, drawdown varied between 0.5 and 1.5 ft. through September 25 when completed.

True color aerial photography was collected on or near peak drawdown on July 15, 2005 (L&D 5 Discharge 30,600 cfs; L&D 5 Elevation 657.94 ft.; Alma Elevation 659.80 ft.). A GIS database for land exposed on July 15, 2005, was developed based on classified land cover types. The extent of substrate exposed on July 15 was determined to be approximately 1,002 acres or 7.4% of the 13,515-acre study area.

Status (2006)

Another drawdown was planned for 2006 and beginning June 12, water levels were gradually reduced to about 1.5 ft. below the normal elevation at L&D 5 by June 26. However, because of the low and declining river flows this summer, river managers were only able to hold a full 1.5-ft. drawdown at the dam for a couple of days before having to shift to "primary control" and the pool water level was raised accordingly.

2004-08-13_p5_aerial.zip (24.4 MB) This imagery provides a photo mosaic from aerial photography collected on August 13, 2004 and serves as the pre-drawdown reference condition for vegetation communities. Aerial photo scale: 1:12,000 Resolution: 1.0 meter/pixel World file contains coordinates for UTM Zone 15, NAD83 and NAD27
2005-07-15_p5_aerial.zip (26.3 MB) This imagery provides a photo mosaic from aerial photography collected on July 15, 2005.  The photography was collected during the approximate maximum extent of drawdown (L&D 5 Discharge- 30,600 cfs. L&D 5 Elevation- 657.94’,   Alma Elevation- 659.80’) and was used to determine the area of substrate exposed with the drawdown. Aerial photo scale: 1:12,000 Resolution: 1.0 meter/pixel World file contains coordinates for UTM Zone 15, NAD83 and NAD27
2005-08-28_p5_aerial.zip (43.5 MB) This imagery provides a photo mosaic from aerial photography collected on August 28, 2005 and represents period of peak biomass for most plant communities in summer 2005. Aerial photo scale: 1:12,000 Resolution: 1.0 meter/pixel World file contains coordinates for UTM Zone 15, NAD83 and NAD27
This ArcView shapefile was developed from the July 15, 2005 aerial photography and based on land cover types growing on the exposed substrate only.  The extent of substrate exposed was determined to be approximately 1,002 acres. p5dd_2005_exposed_n83.zip (167 KB) ArcView shapefile created by on-screen digitizing the exposed substrate visible on the July 15, 2005, aerial photo mosaic and projected in UTM Zone 15, NAD83. p5dd_2005_exposed_n27.zip (175 KB) ArcView shapefile created by on-screen digitizing the exposed substrate visible on the July 15, 2005, aerial photo mosaic and reprojected to UTM Zone 15, NAD27.