The roles of man-made weirs were well-known as flooding control in summer monsoon, but the function of wintering habitat for wintering water birds were not revealed. This study examined the effects of man-made weirs on the wintering distribution of water birds in Tancheon Stream, Korea, with a focus on the effects of freeze-thaw process. Data collected during January to February 2003 included thawed water surface ratios, water depths, sandbar areas, and bird distribution under different weather conditions. The analysis revealed a strong positive correlation between thawed surface areas in front of weir’s drop structures and the abundance of dabbling and diving water birds during severe cold conditions with temperatures below - 9°C. However, it was also observed that the stagnant water impounded by the weirs tended to freeze easily in winter, making it difficult for water birds to inhabit those areas. These results suggest an adaptation process against man-made weirs by wintering water birds in urban streams, provide significant insights for improving the function of weirs to enhance water birds’ habitats, especially in urban stream management.

This paper proposes a model based on gene expression programming for predicting discharge coefficient of triangular labyrinth weirs. The parameters influencing discharge coefficient prediction were first examined and presented as crest height ratio to the head over the crest of the weir (p/y), crest length of water to channel width (L/W), crest length of water to the head over the crest of the weir (L/y), Froude number (F=V/√(gy)) and vertex angle () dimensionless parameters. Different models were then presented using sensitivity analysis in order to examine each of the dimensionless parameters presented in this study. In addition, an equation was presented through the use of nonlinear regression (NLR) for the purpose of comparison with GEP. The results of the studies conducted by using different statistical indexes indicated that GEP is more capable than NLR. This is to the extent that GEP predicts the discharge coefficient with an average relative error of approximately 2.5% in such a manner that the predicted values have less than 5% relative error in the worst model.

Simple weir irrigation was recently introduced in rural areas of Zambia. This irrigation technique is based on gravity diversion of the river flow using simple weirs. This study was conducted between November 2022 to January 2023 in 3 northern region provinces (Luapula, Copperbelt, and North-western) of Zambia to perform a diagnostic assessment on simple weirs during the dry and the wet seasons. In this study, 15 single-line simple weirs were selected. The objective of the study is to assess the physical status, identify problems and extent, and estimate water diversion potential by each single-line weir. The findings of this study showed that 67% of weirs were in excellent status (recently maintained and repaired), and 26% of the weirs were partially damaged (leakages, decayed thatch grass). The study revealed that single-line weirs were able to raise a flood height of 0.1m at low flow and 0.5m at medium flow. It was found that single-line weirs in excellent condition diverted more than 90% of the river flow while poorly maintained weirs diverted below 45% of the river discharge. Based on the findings, Single-line weirs have the potential to assist small-scale farmers in accessing river water for irrigation purposes through diversion.