The new Scientific Decade 2013-2022 of IAHS, entitled Panta RheiEverything Flows, is dedicated to research activities on change in hydrology and society. The purpose of Panta Rhei is to reach an improved interpretation of the processes governing the water cycle by focusing on their changing dynamics in connection with rapidly changing human systems. The practical aim is to improve our capability to make predictions of water resources dynamics to support sustainable societal development in a changing environment. The concept implies a focus on hydrological systems as a changing interface between environment and society, whose dynamics are essential to determine water security, human safety and development, and to set priorities for environmental management. The Scientific Decade 2013-2022 will devise innovative theoretical blueprints for the representation of processes including change and will focus on advanced monitoring and data analysis techniques. Interdisciplinarity will be sought by increased efforts to connect with the socio-economic sciences and geosciences in general. This paper presents a summary of the Science Plan of Panta Rhei, its targets, research questions and expected outcomes.

/pdf/panta-rhei-everything-flows-change-in-hydrology-and-society-3i1k3dq1vy.pdf

“Panta Rhei—Everything Flows”: Change in hydrology and society—The IAHS Scientific Decade 2013–2022

'Panta Rhei - Everything Flows': Change in hydrology and society - The IAHS Scientific Decade 2013-2022

A review of SWAT applications, performance and future needs for simulation of hydro-climatic extremes

In response to the continually increasing sediment concentrations in rivers and lakes, the Ethiopian government is leading an effort where farmers are installing soil and water conservation measures to increase infiltration and reduce erosion. This paper reports on findings from a four year study in the 95 ha Debre Mawi watershed where under the government led conservation works, mainly terraces with infiltration furrows were installed halfway in the period of observation. The results show that runoff volume decreased significantly after installation of the soil and water conservation practices but sediment concentration decreased only marginally. Sediment loads were reduced mainly because of the reduced runoff. Infiltration furrows were effective on the hillsides where rain water could infiltrate, but on the flat bottom lands that become saturated with the progress of the monsoon rain, infiltration was restricted and conservation practices became conduits for carrying excess rainfall. This caused the initiation of gullies in several occasions in the saturated bottomlands. Sediment concentration at the outlet barely decreased due to entrainment of loose soil from unstable banks of gullies in the periodically saturated bottom areas. Since most uphill drainage were already half filled up with sediments after two years, long term benefits of reducing runoff can only be sustained with continuous maintenance of uphill infiltration furrows.

https://sciendo.com/pdf/10.1515/johh-2015-0021

Impact of conservation practices on runoff and soil loss in the sub-humid Ethiopian Highlands: The Debre Mawi watershed

Effects of land cover, topography, and soil on stream water quality at multiple spatial and seasonal scales in a German lowland catchment

Extensive lowland floodplains cover substantial parts of the glacially formed landscape of Northern Germany. Stream power is recognized as a force of formation and development of the river morphology and an interaction system between channel and floodplain. In order to understand the effects of the river power and flood power, HEC-RAS mod- els were set up for ten river sections in the Upper Stor catchment, based on a 1 m digital elevation model and field data, sampled during a moderate water level period (September, 2011), flood season (January, 2012) and dry season (April, 2012). The models were proven to be highly efficient and accurate through the seasonal roughness modification. The co- efficients of determination (R 2 ) of the calibrated models were 0.90, 0.90, 0.93 and 0.95 respectively. Combined with the continuous and long-term data support from SWAT model, the stream power both in-channel and on the floodplain was analysed. Results show that the 10-year-averaged discharge and unit stream power were around 1/3 of bankfull discharge and unit power, and the 10-year-peak discharge and unit stream power were nearly 1.6 times the bankfull conditions. Unit stream power was proportional to the increase of stream discharge, while the increase rate of unit in-channel stream power was 3 times higher than that of unit stream power on the floodplain. Finally, the distribution of the hydraulic pa- rameters under 10-years-peak discharge conditions was shown, indicating that only 1-10% of flow stream was generated by floodplain flow, but 40-75% volume of water was located on the floodplain. The variation of the increasing rate of the stream power was dominated by the local roughness height, while the stream power distributed on the floodplain mainly depended on the local slope of the sub-catchment.

/pdf/simulation-and-comparison-of-stream-power-in-channel-and-on-rx2fclbxd4.pdf

Simulation and comparison of stream power in-channel and on the floodplain in a German lowland area

With increased interest and requirements in surface water quality and hydrodynamics, additional information is needed about water flow in streams. The mobile OTT Qliner with acoustic Doppler technology (ADQ) provides a highly efficient and accurate way of collecting this information. For this study we completed 366 measurements of flow velocity, water depth and discharge with ADQ from September 2010 to June 2011 at 174 cross-sections in eight catchments of different sizes located in northern Germany, central Germany and southeastern China. The measurements were used to study the accuracy, reproducibility and sensitivity of the device, and to improve the hydrodynamic sampling for medium-sized rivers and channels by investigating its internal settings. The observations reported clearly show that the results of flow average, profile, layer and point values obtained with the ADQ compare very well with those of electromagnetic or ultrasonic devices. In general, the average flow velocity gives the high...

https://www.tandfonline.com/doi/pdf/10.1080/02626667.2012.727999

Accuracy, reproducibility and sensitivity of acoustic Doppler technology for velocity and discharge measurements in medium-sized rivers

Simulation, quantification and comparison of in-channel and floodplain sediment processes in a lowland area – A case study of the Upper Stör catchment in northern Germany

Accurate estimation of flow resistance restricts the quality of the hydraulic model performance. In this study, we try to investigate the seasonal dynamic of the Manning’s roughness coefficient (n) based on the one-dimensional hydraulic model HEC-RAS in a German lowland area. We set up four river section models based on the 1 m digital elevation model and field measurements, in which the seasonal roughness factors were calibrated and validated with the gauge record. The results revealed that: 1) the Manning’s n varied from 46% to 135% from the base value in autumn; 2) adopting the seasonal roughness factor improved the quality of the model output; 3) the vegetation condition and water elevation dominated the Manning’s n in summer (April–September) and winter (October–March) half year respectively. Water temperature increased the flow resistence in winter half year; 4) the peak value of Manning’s n appeared in late summer due to the highest biomass, while the minimum roughness occurred in early-spring because of the combined influence of low biomass, high water level and relatively higher temperature. The involvement of seasonal roughness factor improved the model performance and the results are comparable to the previous research of the same area.

Seasonality of Roughness - the Indicator of Annual River Flow Resistance Condition in a Lowland Catchment

Seldom studied before, the vertical profile velocity is indicative of the flood process and nutrient transportation process. In this paper, a substitution of cross section hydraulic radius with vertical depth was made to the Manning formula, which was then applied in the vertical profile velocity determination. Simultaneously, the determination accuracy and its relationship with hydraulic conditions were discussed, based on the 1050 vertical profiles sampled from 140 cross sections in flood and moderate level seasons. The observations show the following. (1) The modified Manning formula provides a simplified approach for vertical profile velocity determination with acceptable accuracy. (2) The fitting quality of the profile velocity from the middle region of the cross section and the flood season were higher than that from near the bank or the moderate level season. The coefficient of determination (R2) of the regression for the moderate level season and the flood season were 0.55 and 0.58, while the Nash–Sutcliffe coefficients were 0.64 and 0.82, respectively. (3) Analysis of the determination error and the coefficient of variation showed a positive correlation with the river aspect ratio. This seems to suggest that the modified Manning formula tends to be more applicable in narrow and deep rivers. More measurements from rivers or channels with a high aspect ratio would be meaningful for future research.

/pdf/application-of-modified-manning-formula-in-the-determination-2sdg8qfgfd.pdf

Song Song

Papers

Simulation and comparison of stream power in-channel and on the floodplain in a German lowland area

Accuracy, reproducibility and sensitivity of acoustic Doppler technology for velocity and discharge measurements in medium-sized rivers

Simulation, quantification and comparison of in-channel and floodplain sediment processes in a lowland area – A case study of the Upper Stör catchment in northern Germany

Seasonality of Roughness - the Indicator of Annual River Flow Resistance Condition in a Lowland Catchment

Application of modified Manning formula in the determination of vertical profile velocity in natural rivers