Combining satellite radar altimetry, SAR surface soil moisture and GRACE total storage changes for model calibration and validation in a large ungauged catchment

The availability of data is a major challenge for hydrological modelling in large parts of the world. Remote sensing data can be exploited to improve models of ungauged or poorly gauged catchments. In this study we combine three datasets for calibration and validation of a rainfall-runoff model of the ungauged Okavango catchment in Southern Africa: (i) Surface soil moisture (SSM) estimates derived from SAR measurements onboard the Envisat satellite; (ii) Radar altimetry measurements by Envisat providing river stages in the tributaries of the Okavango catchment, down to a minimum width of about one hundred meters; and (iii) Temporal changes of the Earth’s gravity field recorded by the Gravity Recovery and Climate Experiment (GRACE) caused by total water storage changes in the catchment. The SSM data are compared to simulated moisture conditions in the top soil layer. They cannot be used for model calibration but support bias identification in the precipitation data. The accuracy of the radar altimetry data is validated on gauged subbasins of the catchment and altimetry data of an ungauged subbasin is used for model calibration. The radar altimetry data are important to condition model parameters related to channel morphology such as Manning’s roughness. GRACE data are used to validate the model and to condition model parameters related to various storage compartments in the hydrological model (e.g. soil, groundwater, bank storage etc.). As precipitation input the FEWS-Net RFE, TRMM 20 3B42 and ECMWF ERA-Interim data sets are considered and compared

Sediment Transport Monitoring and Short Term Modeling in the Okavango Delta, Botswana

The Okavango Delta of northern Botswana comprises large wetlands that spread over an alluvial fan of 150km in length. Only part of the fan is covered with wetlands but the repeated shifting of the zones prone to inundation has led to a regular distribution of sediments and eventually to the formation of a smooth fan surface. We conducted repeated solute and bedload transport measurements at the inlet and within the wetlands proper to quantify sediment input and channel aggradation rates. The relationship between flow velocity and bedload transport was used to simulate channel erosion and aggradation, and a bedload transport component was built into a numerical hydrological model of the Okavango Delta. The model was used to assess the impact of a hypothetical dam in the upstream of the wetlands on channel bed elevations and the distribution of flooded areas. Our results suggest that the contribution of solute inputs to the overall sediment accumulation of the fan has been overestimated relative to bedload inputs. The numerical simulations reveal that a dam would have an impact on channel elevations only in its immediate downstream, but an impact on the distribution of flooding would be felt over the entire wetland syste

Combining satellite radar altimetry, SAR surface soil moisture and GRACE total storage changes for hydrological model calibration in a large poorly gauged catchment

The availability of data is a major challenge for hydrological modelling in large parts of the world. Remote sensing data can be exploited to improve models of ungauged or poorly gauged catchments. In this study we combine three datasets for calibration of a rainfall-runoff model of the poorly gauged Okavango catchment in Southern Africa: (i) surface soil moisture (SSM) estimates derived from radar measurements onboard the Envisat satellite; (ii) radar altimetry measurements by Envisat providing river stages in the tributaries of the Okavango catchment, down to a minimum river width of about one hundred meters; and (iii) temporal changes of the Earth's gravity field recorded by the Gravity Recovery and Climate Experiment (GRACE) caused by total water storage changes in the catchment. The SSM data are shown to be helpful in identifying periods with over-respectively underestimation of the precipitation input. The accuracy of the radar altimetry data is validated on gauged subbasins of the catchment and altimetry data of an ungauged subbasin is used for model calibration. The radar altimetry data are important to condition model parameters related to channel morphology such as Manning's roughness. GRACE data are used to validate the model and to condition model parameters related to various storage compartments in the hydrological model (e.g. soil, groundwater, bank storage etc.). As precipitation input the FEWS-Net RFE, TRMM 3B42 and ECMWF ERA-Interim datasets are considered and compared

Regional review: the hydrology of the Okavango Delta, Botswana—processes, data and modelling

The wetlands of the Okavango Delta accommodate a multitude of ecosystems with a large diversity in fauna and flora. They not only provide the traditional livelihood of the local communities but are also the basis of a tourism industry that generates substantial revenue for the whole of Botswana. For the global community, the wetlands retain a tremendous pool of biodiversity. As the upstream states Angola and Namibia are developing, however, changes in the use of the water of the Okavango River and in the ecological status of the wetlands are to be expected. To predict these impacts, the hydrology of the Delta has to be understood. This article reviews scientific work done for that purpose, focussing on the hydrological modelling of surface water and groundwater. Research providing input data to hydrological models is also presented. It relies heavily on all types of remote sensing. The history of hydrologic models of the Delta is retraced from the early box models to state-of-the-art distributed hydrological models. The knowledge gained from hydrological models and its relevance for the management of the Delta are discusse

Blacklists and Whitelists To Tackle Predatory Publishing: a Cross-Sectional Comparison and Thematic Analysis.

We aimed to develop an in-depth understanding of quality criteria for scholarly journals by analyzing journals and publishers indexed in blacklists of predatory journals and whitelists of legitimate journals and the lists' inclusion criteria. To quantify content overlaps between blacklists and whitelists, we employed the Jaro-Winkler string metric. To identify topics addressed by the lists' inclusion criteria and to derive their concepts, we conducted qualitative coding. We included two blacklists (Beall's and Cabells Scholarly Analytics') and two whitelists (the Directory of Open Access Journals' and Cabells Scholarly Analytics'). The number of journals per list ranged from 1,404 to 12,357, and the number of publishers ranged from 473 to 5,638. Seventy-two journals and 42 publishers were included in both a blacklist and a whitelist. Seven themes were identified in the inclusion criteria: (i) peer review; (ii) editorial services; (iii) policy; (iv) business practices; (v) publishing, archiving, and access; (vi) website; and (vii) indexing and metrics. Business practices accounted for almost half of the blacklists' criteria, whereas whitelists gave more emphasis to criteria related to policy. Criteria could be allocated to four concepts: (i) transparency, (ii) ethics, (iii) professional standards, and (iv) peer review and other services. Whitelists gave most weight to transparency. Blacklists focused on ethics and professional standards. Whitelist criteria were easier to verify than those used in blacklists. Both types gave little emphasis to quality of peer review. Overall, the results show that there is overlap of journals and publishers between blacklists and whitelists. Lists differ in their criteria for quality and the weight given to different dimensions of quality. Aspects that are central but difficult to verify receive little attention. Predatory journals are spurious scientific outlets that charge fees for editorial and publishing services that they do not provide. Their lack of quality assurance of published articles increases the risk that unreliable research is published and thus jeopardizes the integrity and credibility of research as a whole. There is increasing awareness of the risks associated with predatory publishing, but efforts to address this situation are hampered by the lack of a clear definition of predatory outlets. Blacklists of predatory journals and whitelists of legitimate journals have been developed but not comprehensively examined. By systematically analyzing these lists, this study provides insights into their utility and delineates the different notions of quality and legitimacy in scholarly publishing used. This study contributes to a better understanding of the relevant concepts and provides a starting point for the development of a robust definition of predatory journals

Assessing the utility of geospatial technologies to investigate environmental change within lake systems

Over 50% of the world's population live within 3. km of rivers and lakes highlighting the on-going importance of freshwater resources to human health and societal well-being. Whilst covering c. 3.5% of the Earth's non-glaciated land mass, trends in the environmental quality of the world's standing waters (natural lakes and reservoirs) are poorly understood, at least in comparison with rivers, and so evaluation of their current condition and sensitivity to change are global priorities. Here it is argued that a geospatial approach harnessing existing global datasets, along with new generation remote sensing products, offers the basis to characterise trajectories of change in lake properties e.g., water quality, physical structure, hydrological regime and ecological behaviour. This approach furthermore provides the evidence base to understand the relative importance of climatic forcing and/or changing catchment processes, e.g. land cover and soil moisture data, which coupled with climate data provide the basis to model regional water balance and runoff estimates over time. Using examples derived primarily from the Danube Basin but also other parts of the World, we demonstrate the power of the approach and its utility to assess the sensitivity of lake systems to environmental change, and hence better manage these key resources in the future