Water balance of the Saint John River Basin

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University of New Brunswick


The Saint John River Basin lies in a broad arc across south-eastern Quebec, northern Maine and western New Brunswick. The total drainage area is 55146 km2 , of which 51 percent is in New Brunswick. The objective of this project is to produce regional scale mapping o f the variability of average annual runoff and evapotranspiration within the New Brunswick portion of the basin. Maps of average annual runoff, precipitation and evapotranspiration are produced for the basin using Surfer mapping software. The average runoff for the basin was calculated to be 0.678 m. The average precipitation within the basin was calculated to be 1.127 m. Average annual evapotranspiration across the basin was calculated at 0.449 m. These calculations result in 40 percent of precipitation being returned to the atmosphere with 60 percent runoff. A plot of the variability of averages concludes that these results are not representative of the basin. When a contour map of the averages is constructed, variability of runoff average becomes apparent. The expected runoff average o f 40 percent can be seen in areas where there is a higher density of data points. The trend suggests that the plot conforms to the expected 40 % runoff values and is only limited by the density of data points. It can be concluded that this method to calculate average annual runoff and evapotranspiration is a valid method for regional mapping. This method of runoff mapping, however is progressively less accurate as calculations are advanced down stream.