Water balance and irrigation scheduling in the forest nursery, Koksilah, British Columbia : a case study
Date
1977
Authors
Stubbs, Kenneth Peter
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Abstract
This paper studies evapotranspiration and irrigation needs in Douglas fir seeding beds at the British Columbia Forest Nursery, Koksilah, British Columbia.
Research data were collected over the summer of 1970 and 1971, Potential evapotranspiration was measured through the use of a two-·bin drainage lysimeter. Climatic elements measured were temperature, relative humidity, hours of sunshine, precipitation and windspeed.
The applicability of existing methods for the prediction of potential evapotranspiration was tested through a correlation analysis. Results indicated that no formula gave reliable predictions at Koksilah.
The measured climatic elements were tested for their individual relationships to potential evapotranspiration. Using a ten day running average, hours of sunshine explained the lowest percentage (66%) while maximum relative humidity explained the highest percentage (97%) of variation in measured potential evapotranspiration.
The individual climatic elements were tested in various combinations through a multiple regression analysis. The combination of maximum temperature, minimum temperature, and average windspeed explained J9 percent of the variation in potential evapotrru1spiration readings, This method required much less detailed data and less calculation than existing formulae. The results achieved using this combination were more reliable than those obtained using the existing formulae.
From the newly developed formula, a nomograph and table were developed by which the actual evapotranspiration (i.e. irrigation needs) can rapidly be determined.