The water chamber must be as level as possible. The support frame (fig. 6) is 

 adjustable so that the water chamber can be leveled on slopes up to 60 percent. This 

 could be increased up to about 85 percent by increasing the length of the slots in the 

 slotted bars [9]. The bolts that attach the upright members to the base are secured 

 with locknuts and are left loose enough to allow the limited rotation required for 

 leveling. The collector trough [10] is made from a single piece of sheet steel bent 

 as indicated in figure 6. 



The inf iltrometer is set up and operated as follows. The water applicator is 

 placed over the area to be tested. A sensitive level is placed on the water chamber 

 and the chamber is leveled along both axes by means of the leveling mechanism [9] and 

 by moving the applicator slightly, if necessary. On steep or slippery slopes the 

 applicator is held in position by stakes driven into the ground inside the upper two 

 corners of the base. After the applicator has been positioned, the runoff collecting 

 trough [10] is installed with its upper edge directly below the lower edge of the 

 applicator. It should be installed slightly beloiv the soil surface, and, if necessary, 

 the uphill edge sealed to the soil surface with caulking compound. A small hole is dug 

 under the outlet of the trough to allow placement of a tin can such as a 2- or 3 -pound 

 coffee can [11] . 



The reservoir is filled and connected to the water chamber. The tubing clamp is 

 opened to allow free flow of water into the water chamber. Few raindrops are produced 

 while the chamber is filling. As soon as the chamber is filled and water moves into 

 the manometer [8], the tubing clamp is quickly adjusted to the desired flow. Rainfall 

 commences as soon as water appears in the manometer and, from then on, its rate responds 

 almost instantaneously to changes in flow-meter readings. It is usually necessary to 

 readjust the tubing clamp from time to time. The reservoir can be refilled during the 

 test if the flow rate is kept reasonably constant by means of the tubing clamp. Runoff 

 into the tin can is measured at desired intervals in a 1,000-ml. graduated cylinder. 

 At the end of the test, water application can be stopped abruptly by kinking the supply 

 tubing and closing the tubing clamp. 



Some clogging of the steel tubes can be expected, but can be minimized by using 

 only clean water and by using a screened funnel for filling the reservoir. Distilled 

 water might give better results, but we used tapwater from city supplies and campgrounds 

 and experienced only minor clogging. If a tube clogs, it can be cleaned by pushing a 

 small steel wire up the bore of the tube. 



Rainfall intensities from about 1/2 inch per hour to about 10 inches per hour can 

 be obtained with this infiltrometer . The inf iltrometer was calibrated at several inten- 

 sities by operating it on a metal sheet; the results agreed closely with the flow-meter 

 manufacturer's calibration chart. 



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