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" 9 For the months of July and August the diminishing trend has two phases. The first detectable change began around 1951, and a second one ten years later in 1961. This may have been caused by the intensified use of 9roundwater from the alluvium of the river valley starting in the early 1950's. This trend has reversed durin9 recent years in September and October, probably reflecting the affect of return flows from Colorado- Big Thompson water applied late in the irrigation season + return flows from pumped water. .' 2. The linear correlation coefficient of the water year data shows a fairly close relationship of the variables. This index is also fairly high for months during the irrigation, but tends to be lower during the non-irrigation season--particularly January. Tabulated below are the least square regression line equations by months and for the water year along with the linear correlation coef- ficients, "r.lI Month , January February March April May June July August September October November December Water Year .' Iguation .. Return Return Return Return Return Return Return Return Return Return Return Return Return flow = 0.41 flow = 0.60 flow = 0.83 flow = 0.74 flow = 0.63 flow = 0.43 flow = 0.72 flow = 0.76 flow = 0.52 flow = 0.61 flow = 0.81 flow = 0.68 flow = 0.66 10,510 5,680' 280 660 7,300 29,980 14,050 14,790 22,610 13,090 900 3,420 101,553 In flow + Inflow + Inflow Inflow + In flow + Inflow + Inflow + Inflow + In flow + In flow + Inflow - In flow + Inflow + Comparison of Inflows and Total Diversions Correlation Coefficient 0.68 0.86 0.95 0.96 0.87 0.95 0.96 0.92 0.90 0.86 0.91 0.87 0.92 The same inflow variables were used in these analyses as defined in the previous section. The "total diversions. variable consists of the total water diverted by each ditch having its headgate between the Henderson and Kersey gages regardless of water type. The time span of the analyses were 1956 through 1966. However, because of l.ack of winter diversions, only months belonging to the irri- gation ~ason (April through October) have been used and similarly the total yearly figure is represented by the seasonal sum. The relatedness of diversions to existing inflows is only moderate to poor. Early and late irrigation diversions are inversely proportional to the inflows and only in July and August is there a dir~ct or positive relationship. This indicates a generally stable irrigation pattern in the early and late season, with a direct dependence on the amount of in- flows in July and August. "