Habitat Evaluation of Agricultural Waterways where Environmental Improvement Was Practiced for Recreation

Abstract

In rural areas, agricultural irrigation and drainage systems developed for paddy fields have a high potential to become components of green infrastructure by providing ecosystem services. In order to manage and operate agricultural waterways as green infrastructure, the habitat evaluation of aquatic organisms is important. In this context, we conducted a habitat evaluation of aquatic organisms in the waterway network where environmental improvement was practiced to promote recreational use by residents. Based on evaluation results, the physical characteristics of canals with high biodiversity were investigated. The Evaluation Program for Fish Habitats in Agricultural Canals, which was developed for non-professional users such as residents, was applied to biological (fishes and crustaceans) and physical data collected in the waterway network in the town of Koura, Shiga Prefecture, Japan. The model generated by the program showed high fitness (0.80 for fishes, 0.76 for crustaceans), which suggests the program applies to waterway networks including various types of watercourses. The characteristics of the canals which were assigned a high habitat score by the program included 1) deeper water depth, 2) higher velocity for fish, 3) lower velocity, 4) higher vegetation coverage, and 5) gravel canal bed for crustaceans, relative to the low-scoring canals. The canals in diversion parks developed as part of environmental improvement efforts tended to have these characteristics and higher scores. Therefore, our findings suggest that conserving irrigation canals and developing diversion parks in waterway networks, which were conducted as part of environmental improvement efforts in the target area, contributes not only to promoting recreational use by residents but also to habitat conservation.