A stochastic model for behaviour of fish ascending an agricultural drainage system

Abstract

Adults of Carassius auratus grandoculis ascend from Lake Biwa, Japan, into riparian paddy fields via agricultural drainage systems for the purpose of spawning. However, land improvement works conducted in the second half of the twentieth century have brought about obstacles for passage of the fish, and several restoration projects to recover the migratory environment are being attempted. A continuous Markov process model is presented to scientifically support such a project, defining an ascending probability that quantitatively assesses the ability of an agricultural drainage system with hydraulic structures for the ascent of the fish. Computational methods are developed to numerically obtain flow fields of the agricultural drainage system and then the ascending probability in the entire spatio-temporal domain. The values of model parameters are deductively inferred, referring to results of field observations. From the computational results of the ascending probability in the agricultural drainage system, effects of hydraulic structures allowing ascent of the fish are clarified.

Internal Boundary Conditions for Solute Transport Equations in Locally One-dimensional Open Channel Networks

“…The set of the reaches of : is denoted by R : . : is assumed not to have abrupt bed elevation changes at a junction that requires the use of a specific IBC, which is beyond the scope of this paper (Unami et al, 2010). Assuming no external water exchange at junctions, the mass conservation of water…”

Concurrent use of finite element and finite volume methods for shallow water flows in locally 1‐D channel networks

“…Fan et al [3] studied flooding in a large complicated drainage system including rivers, diversion channels, and lakes. Unami et al [4] simulated flows in an agricultural drainage system to investigate behaviour of fish migration in it.…”