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f,,.,,.,~. I J I' " J 6. A predominant characteristic of the flow at Julesburg, as at other <;to3tlon5 on the South Platte, Is the variability. For example, the highest one-rronth discharge on record (631,000 acre-feet In June of 1921) was nearly twice the long-term average annual discharge. Maximum and minimum monthly volumes of discharge varied from over 100~~ to less than 1% of the 1009- term averages. The greatest range, in terms of volume of water, has occurred in the month of June -- 630.500 acre-feet difference between the maximum and minimum discharges on record. Trends I. The 20-year moving average of the 65 years of flow past the Jules- burg station shows a downward trend in flow. Generally speaking, the average annual discharge during the early part of the period of analysl5 was 100,000 to 125.000 acre-feet more than during the more recent years. 2. Twenty-year moving averages for the months of June, Au~ust, S€ptem- ber, October, November and December have a pattern simi lar to the annual pat tern. 3. Twenty-year moving averages for the months of January, February, March, April and May show no discernible trend. 4. The 20-year moving average for the month of July shows a 51 ight upward trend over the 65-year period. Comparison of Flows at Julesburq and Balzac Correlation analyses and double-mass curves were used to study the relationships of the flow at Julc'jburg with the flow in the South Platte River at other upstream stations, and to determine the change in these re- lat ionships, if any. The following items sunmarize the results of analyses comparing Julesburg with Balzac: I. A high linear correlation (r = 0.98) exists between the annual flow at Julesburg and the annual flow at Balzac. For the 39-year perIod from 1928 to 1966 the best-fit linear equat ion expressing the relationship between the flows at these two stat ions was: Julesburg flow = 1.04 10( Balzac + 45,130 acre-feet. This indicates that normally the net gain in the river in this section arrounts to 51ightly more than 45,000 acre-feet. regardless of the total volume of flow. 2. The double-mass plot of flows at Julesburg vs. flows at Balzac shows a very 51 iQht trend tow~rds a reduction in annual flow at Julesburg compared to Balzac during recent years. This trend started In 1946. then reversed itself during the period 1950 through 1952, but has returned to the diminishing situation at Julesburg since 1952. However, the 1952-62 period shows a relationship almost Identical to that of the 1931-41 period.