Experimental data related to the analysis of reservoir geometry effects on dam-break flows are provided. Four different reservoir plan shapes were considered, namely a long reservoir, a wide, a trapezoidal shaped and one with a 90° bend. Time variations of the water level were measured with ultrasonic sensors and a high-speed camera. Velocity components were recorded using an acoustic Doppler velocimeter. It was observed that 2D effects are enhanced in the wide and trapezoidal reservoirs and that the long and 90° bend reservoirs produce similar results, with a mainly 1D flow. Finally, discharge estimates based on the water level and velocity data were compared with predictions by empirical formula. Due to the simplified geometry considered, existing formulae are only indicative and cannot be directly applied to practice.

Development of environmental flow standards at the regional scale has been proposed as a means to manage the influence of hydrological alterations on riverine ecosystems in view of the rapid pace of global water resources management. Flow regime classification forms a critical part in such environmental flow assessments. We present a national-scale classification of hydrological regimes for Iran based on a set of hydrological metrics. It describes ecologically relevant characteristics of the natural hydrological regime derived from 15- to 47-year-long records of daily mean discharge data for 539 streamgauges within a 47-year period. The classification was undertaken using a fuzzy partitional method within Bayesian mixture modelling. The analysis resulted in 12 classes of distinctive flow regime types that differ in various hydrological aspects. This classification is being used for further research in regional-scale environmental flow studies in Iran.