No abstract

No abstract

No abstract

Abstract:This study analyses the increasing number of catastrophic floods in the Niger River Basin, focusing on the relation between long term hydro-climatic variability and flood risk over the last 40 to 100 years. Time series for three subregions (Guinean, Sahelian, Benue) show a general consistency between the annual maximum discharge (AMAX) and climatic decadal patterns in West Africa regarding both trends and major changepoints. Variance analysis reveals rather stable AMAX distributions except for the Sahelian region, implying that the changes in flood behavior differ within the basin and affect mostly the dry Sahelian region. The timing of the floods within the year has changed only downstream of the Inner Niger Delta due to retention processes. The results of the hydro-climatic analysis generally correspond to the presented damage statistics on people affected by catastrophic floods. The damage statistics shows positive trends for the entire basin since the beginning in the 1980s, with the most extreme increase in the Middle Niger.

Using concepts of connectivity in challenges regarding land and water management (flooding, erosion, nutrient leaching, landslides) can only be fully harnessed if knowledge is communicated well between scientists and stakeholders. Proper communication requires prior understanding of end‐users' perception of connectivity as a useful framework. Therefore, we analysed (a) perceptions of ‘connectivity’ for stakeholders involved in water and land management across Europe, (b) potential for stakeholders to apply connectivity‐related measures in their management decisions, (c) stakeholders' biggest challenges in water and land management, and (d) stakeholders' expectations for future connectivity research agendas. We studied 85 questionnaires from 19 countries using a grounded theory approach. One third of stakeholders understood connectivity in its scientific context, whereas 39% perceived connectivity indirectly through their personal experiences (e.g., water and sediment fluxes and erosion). Half of stakeholders' perceived links and challenges were related to availability of data and methods, communication, and institutions or policy, whereas others believed they were related to water quality and quantity, soil erosion and quality, and climate change. Half of the stakeholders considered connectivity management important, and one third showed high interest in managing connectivity. Adopting connectivity into management is hindered by institutional‐ and policy‐based management limitations, insufficient data and methods, and ineffective knowledge transfer. Explicitly considering heterogeneity of stakeholder perceptions is required for projects regarding management of connectivity at European, national, and local scales.

Core Ideas The monitoring system synchronizes soil water extraction with real drainage periods. It is remote controllable and has SMS notification in case of automated sampling initiation. It is easy to duplicate using commonly available measuring equipment. The system can monitor field soil solute fluxes, such as contaminant migration. To estimate potential risks of groundwater contamination, national and international environmental legislation stipulates standard values referred to pollutant contents in the soil and more rarely referred to loads in the soil leachate. Although in situ soil leachate analysis yields more realistic drainage water quality estimates than soil contamination level–derived estimates, there is no existing standard for how to explicitly sample soil leachate for the required contaminant migration detection. The objective of this study was to overcome current limitations of soil seepage sampling for detecting a contaminant migration in the unsaturated zone by introducing a technical solution that automatically restricts soil water extraction to drainage periods using active devices such as suction cups. Sampling is triggered by a moisture threshold parameterized according to the respective soil water retention properties defining the onset of a drainage period. We tested our sampling approach on two different bioretention systems in Germany for stormwater drainage quality analysis out of the upper soil layer. We present the monitoring results of the 4‐mo testing phase containing 19 individual storm events illustrating the fundamental functioning of the in situ soil leachate sampling system under different climatic conditions. The results clearly demonstrate the feasibility of restricting soil water extraction to drainage periods by means of actual soil moisture measures and indicate a general transferability of our approach. Our approach is easily duplicable, based on the included technical description, for further studies requiring explicit soil leachate sampling and is likely to help improve the reliability of field‐monitored pollutant migration from contaminated sites.

The timing of short extreme rainstorm, which was usually thought to occur on midsummer afternoons, was investigated to improve future mitigation options for infrastructure and safety from localised flash flooding. Using a peak-over-threshold approach, the timing of 10- and 60-min extreme events was filtered from high-resolution rainfall series assessing diurnal, seasonal, and annual distributions and analysed for spatial variations and prevailing atmospheric circulation types (CTs). The diurnal distribution showed a clear deviation from that of the entire rainfall regime. A complex spatial pattern was identified with distinct timing signatures of storms in the northern (mostly afternoon) and southern regions (a bimodal distribution with a second peak in the early morning) of Germany and a more homogenous diurnal distribution of events across the central regions. Most storms occurred in summer, but 42% of 10-min events occurred outside the summer months (June–July–August). A distinct annual clustering of extremes was identified, which varied distinctly between the 10- and 60-min extremes, indicating that the sub-hourly and hourly events were far from running conterminously. The timing of extreme events on the investigated time scales was not dominated by the occurrence of specific CTs in most cases, suggesting that other factors control these extremes.

Abstract. The article reviews research perspectives and ambitions of connectivity scientists in order to facilitate and improve joint connectivity research efforts across disciplinary boundaries. The assessment of four very different viewpoints (pragmatic, conceptual, epistemological and ontological) on connectivity signifies the diversity of thought and practice in the connectivity community and calls for a structured way to ensure mutual understanding in collaborative settings. The shared mental model approach is introduced with an exploratory case study as a way to overcome persistent barriers in understanding by identifying gaps and overlaps of individual researchers' perspectives and knowledge that should help improve collaboration in this interdisciplinary environment.