ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

where Consumptive Use = evapotranspiration plus interception, Input = precipitation
(measured in open areas as close to the site as possible); and n Soil Moisture = change
in soil water within the profile as determined by a nuclear moisture gauge.
Although soil water may have passed through the root zone and mistakenly attributed
to consumptive use, most moisture levels were already on the decline at the time of
initial measurement in early spring. We assumed that no appreciable amounts of water
were lost below the root zone after our first spring measurement.
A modif ied N. P.D. C. (Neutron Probe Data Conversion) computer program was used
to compile total daily use for the measurements period.
Early and late season daily use rates, not covered by actual field measurement
(heavy dashed 1 ines in figure 6) were calculated in order to provide comparable use
periods for each year. This procedure may cause consumptive water use to be over-
e:. timated as much as 0.5 inch (1.3 cm) per year. However, the errors in total use
differences between residues treatments is very minor (between 0.1 and 0.2 inches
i0.25 and 0.51 cm]) per year, well within the precision of this study. Due to insuf-
ficient daily use rate near the beginning of the 1975 growing season, total water use
was not calculated for that year.
I I 1 I I - 1 7
MAY2 JUNE 1 JULY 1 AUG. 1 SEPT. 1 OCT. 1 OCT. 17
MONTH AND DATE
Figure 6.--Soil water measurement dates and curnuZuLive precipitation for the measure-
menk periods during the 1975 to 1918 growing seasons.