Located in Winfield, Missouri, Lock and Dam 25 is the third southern-most dam in the system on the Upper Mississippi River. The dam, which is 1,296 feet long, consists of 14 tainter gates and 3 roller gates. The tainter gates pivot vertically and are raised or lowered to control the depth of the water in the pool upstream of the dam. In times of high water, these gates are raised completely and the river flows almost unimpeded, allowing a more natural flow of the river. The roller gates, located near the center of the dam, also restrict the water flow, but in a manner meant to reduce erosion. The lock chamber consists of four miter gates (two at each end of the chamber), and four valves (two at each end). All boats wishing to pass through a dam must lock through the lock chamber, even during open river conditions. Lockage is completed by using a system of valves to raise and lower the water level in the lock chamber. This is an elevator system for boats; raising or lowering the water adjusts the boats to the necessary pool level. There are two sets of valves on the lock. The filling valves, located near the upper gate, are opened to allow water to enter the chamber, making it the same height as the upper pool. The emptying valves, located near the lower gate, are opened to allow water to drain out, making the chamber the same height as the lower pool. During the process, no pumps are used; the water is moved solely by gravity.

Taken from a low angle in a purpose made tank. Only the lighting has changed Canon 40D and 100mm macro lens, full frame uncroppped image 2 x 580Ex flash guns used for illumination 1/10 sec@ f16 iso 100 Water/milk droplets delivered via a Stopshot controlled solenoid valve. Camera and flashes triggered by a IR beam and StopShot programmable trigger. Snoots removed some water detail is visible but both flashguns zoomed in to reduce the light on the surface 580Ex @ 1/64 on the right aimed at the droplet. 580Ex @ 1/64 aimed at the droplet from the left.