Estimation of baseflow recession constant and regression of low flow indices in eastern Japan

We propose a convenient procedure for the matching strip method in determining the recession constant of the master recession curve using the ratio of flow over successive days (Q n+1 /Q n ). The method is applied to 29 basins (6.1-740 km 2 ) in eastern Japan to develop linear regression models that estimate low flow indices through the recession constant (λ), and either mean annual precipitation or mean annual runoff. Significant models were developed for Q7 10 (seven-day 10-year low flow), and Q97 10 (10-year low flow exceeded 97% of the time) in the case of all basins, and in particular for basins classified into sedimentary or igneous geology (adjusted R 2 up to 0.784). When basins were not classified by geology, models based on mean annual runoff as the second independent variable performed better than those based on mean annual precipitation, with adjusted R 2 values of 0.705 and 0.717 for the Q7 10 and Q97 10 models, respectively.