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10 C. This was accomplished by adjustment of each of the I-inch calibration weights to exactly 823.6 g, equivalent to a water density of 0.9999 g/cm3 which occurs at 0.5 and 7.50C. The Belfort instruction manual (1976) states that each calibration weight weighs 822.7 g and is equivalent to a volume of water one inch deep by 8 inches in diameter (Belfort collector orifice diameter). This would be correct at a temperature of either -6.50 C. or +170 C, where the density of water is 0.9988 g/cm3. The dual-traverse gages were calibrated on 6 October 1982 over the full 12-inch range with cha:rt paper graduated in inches (Chart No. 5-4047-B). Individual cal ibration weights wlere incrementally placed in the catch bucket during the calibration routine. After each weight was centered in the bucket, the gage's bucket was tapped and the chart drive cylinder was manually rotated slightly to record the pen's trace on the chart. This was done for each increment from 0 through 12 inches. The procedure was then reversed~ each of the weights from 12 through 0 inches was removed. Table 1 lists the deviations of each gage from the respective chart inch levels. The calibration checks recorded near the midpoint of the tests are also noted for a single traverse range for each respective gage. After the calibration was complet:ed, the gages and chart drives were considered ready for test exercises. A calibration weight (823.6 g) was pl aced in the cEmter of the catch bucket to position the gage's pen arm at an opElrating range that might be expected under field conditions. Thi.s simulated the weight of an evapora tion suppressant/antifreeze charge that would be used during winter field operations and would bring the initial level of the gage above 0 inches. This procedure also kept the gage from bottoming out on the platform movement stop screws. If the system were to deviate significantly from the zero calibration level, it is possible that considerable flow could enter the catch bucket while resting on the stop screw, and not be detected by the weighing mechanism. After the calibration weight was placed in the catch bucket, a second smaller catch beaker was placed on top of the weight within the bucket to receive the flow from the IV tube. This beaker, with an evaporation suppressant added, was weighed before placement. The volume of evaporation suppressant was approximately 10 cm3 and generally weighed nearly 8.2 g (equivalent to 0.01 inch of precipitation). Texaco aircraft hydraulic oil BB (petroleum base) was used for an evaporation suppressant. The small catch beaker 'was used to allow for convenient weighing of the total flow catch after each test. In addi tion, with a smaller beaker, the is urface area of the 1 iquid was reduced. This required less evaporation suppressant and decreased the opportuni ty for evaporation. 5