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AbstractArid and semi‐arid regions are characterized by limited water availability throughout the year and highly variable streamflows. River channel transmission losses add another uncertainty to the complex flow regimes. However, the contribution of different factors influencing to transmission losses is poorly understood. In this work we determined whether variations in river channel transmission losses along five reaches of varying lengths could be related to reach inflows in Runde River catchment in Zimbabwe. We directly estimated transmission losses as the difference between reach inflow and outflow discharges. Using simple bivariate regression equations, channel transmission losses were modeled as response variables while reach inflows were the predictor variables. Our results indicate statistically significant positive relationships (p = .000, R2 > 0.05) between inflows and transmission losses for all minor, moderate, and major flow events. This simple approach can be applied in similar settings to understand the variations in transmission losses.

AbstractFlows along river reaches decrease in the downstream direction as a result of transmission losses. These losses are important in arid and semi‐arid regions where there is critical water scarcity. Poor quantification of losses compromises the quality of information useful for effective water resources management. This study determined the influence of rainfall variations on transmission loss trends along Runde River in Zimbabwe. Monthly rainfall and flow data from 2010 to 2014 were used in the analysis. Losses were estimated as the difference between reach inflow at an upstream station (E133) and outflow at the downstream station (E83). The Mann–Kendall trend test was applied to detect trends in losses and rainfall data during dry seasons (April–September) and wet seasons (October–March). Results show no significant increasing rainfall and transmission loss trends (S = 2, p > .1) during wet seasons. During dry seasons, rainfall show no significant decreasing trends (S = 4, p > .1) whereas losses show no trends (S = 0). Results also show no significant (p > .05) relationship between rainfall and losses during wet and dry seasons. This simple and quick approach can be applied in similar systems to understand the variations in transmission losses and address otherwise water resource challenges.