2015 Volume 20 Issue 2 Pages 85-92
Three types of upstream-inclined plank weir have been tested in order to develop small-scale fishway for the fishes around paddy fields. The experiments were conducted using leveled-crested upstream-inclined plank weir of rectangular section (Type 1), inclined-crested upstream-inclined plank weir of rectangular section (Type 2), leveled-crested upstream-inclined plank weir of trapezoidal section (Type 3) and leveled-crested vertical plank weir of rectangular section (Control type). The ascending experiments of Orizias sakaizumii and Misgurnus anguillicaudatus were conducted with the water-level difference of 6cm and 9cm between upstream and downstream at the volumetric flow rate of 5.3 and 1.9L/s. The experimental results showed that upstream-inclined plank weirs were superior to vertical plank weir in the rate of ascending and the Type 2 plank weir had stable ascending rates of the two fishes. Multiple linear regression analyses showed that (i) Type 1, Type 3, ascending distance, ascending angle, water temperature, discharge and water-level difference significantly affected the ascending rate of Orizias sakaizumii, (ii) Type 2, Type 3 and ascending angle significantly affected the ascending rate of Misgurnus anguillicaudatus.
