Abstract
Generally, the response of the river water level in an estuary to the river flowrate is far from simple. The main reasons for this are the four competing factors of tide, atmospheric pressure, wind direction and wind speed, whose effects drive the river level to a variety of elevations. The error represented by the average of that dispersed group can at times be over 200%. No matter what statistical analysis is applied, no plausible estimate of the flowrate can be made from the river level. This paper uses data taken in the Ishikari River estuary over the last 5 years to present a quantitative relationship for of the above 4 factors on the level of the Ishikari River. These relationships permit highly precise calculation of the river flowrate, using observed values of the above 4 factors, at any arbitrary location in the estuary.
