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result~ng from high intensity rainstorms. The Purgatoire River is the largest tributary of the Arkansas River in Colorado. Records of the flow of the Purgatoire River reflect the nature of tributary inflows as described above. The only long term records of tributary inflows below Canon City are those on the Purgatoire River. Even here the records of the Purgatoire River at Las Animas are not continuous during the 1908-1984 study period, and corre- lations with other gage records were necessary to estimate the inflow to the Arkansas River. A comparison of the Purgatoire River flows with other tributary inflow for concurrent periods of time revealed that the,Purgatoire contributes more water than any other tributary. Streamflow records for Big Sandy Creek, a major north- side tributary of the Arkansas River below John Martin, are available for the years 1969 to 1982. As indicated in the U.S.G.S. remarks related to these streamflow records, the Big Sandy Creek flows at the gage "are affected by diver- sions above the station and return flow from irrigated areas." Inspection of the daily discharge records iJ,lus- trates these upstream effects. The records show that in - most years there is an unnaturally high increase of flows in about mid-November and a sudden decrease in flows in about April. Upon further investigation, it was determined that these unnatural changes in flow are due to the operations of the Amity Canal Company. In previous years, the Amity Canal has discharged water into the Big Sandy Creek at a point approximately six miles above the gage. This discharge is -27- OJ. ,,/'.