A Comparative Analysis of Altimetry Derived Water Levels with in-situ Gauge Data on River Indus

Author(s):  
Shoaib Jamro ◽  
Talal Naseer ◽  
Arjumand Zaidi ◽  
Stefano Vignudelli
2019 ◽  
Vol 11 (8) ◽  
pp. 899
Author(s):  
Zhaofei Liu ◽  
Zhijun Yao ◽  
Rui Wang

CryoSat-2 altimetry has become a valuable tool for monitoring the water level of lakes. In this study, a concentrated probability density function (PDF) method was proposed for preprocessing CryoSat-2 Geophysical Data Record (GDR) data. CryoSat-2 altimetry water levels were preprocessed and evaluated by in situ gauge data from 12 lakes in China. Results showed that the accuracy of the raw GDR data was limited due to outliers in most of the along-track segments. The outliers were generally significantly lower than the in situ values by several meters, and some by more than 30 m. Outlier detection, therefore, improves upon the accuracy of CryoSat-2 measurements. The concentrated PDF method was able to greatly improve the accuracy of CryoSat-2 measurements. The preprocessed CryoSat-2 measurements were able to observe lake levels with a high accuracy at nine of the twelve lakes, with an absolute mean difference of 0.09 m, an absolute standard deviation difference of 0.04 m, a mean root mean square error of 0.27 m, and a mean correlation coefficient of 0.84. Overall, the accuracy of CryoSat-2-derived lake levels was validated in China. In addition, the accuracy of Database for Hydrological Time Series of Inland Waters (DAHITI) and HYDROWEB water level products was also validated by in situ gauge data.


Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 738
Author(s):  
Nicola Rossi ◽  
Mario Bačić ◽  
Meho Saša Kovačević ◽  
Lovorka Librić

The design code Eurocode 7 relies on semi-probabilistic calculation procedures, through utilization of the soil parameters obtained by in situ and laboratory tests, or by the means of transformation models. To reach a prescribed safety margin, the inherent soil parameter variability is accounted for through the application of partial factors to either soil parameters directly or to the resistance. However, considering several sources of geotechnical uncertainty, including the inherent soil variability, measurement error and transformation uncertainty, full probabilistic analyses should be implemented to directly consider the site-specific variability. This paper presents the procedure of developing fragility curves for levee slope stability and piping as failure mechanisms that lead to larger breaches, where a direct influence of the flood event intensity on the probability of failure is calculated. A range of fragility curve sets is presented, considering the variability of levee material properties and varying durations of the flood event, thus providing crucial insight into the vulnerability of the levee exposed to rising water levels. The procedure is applied to the River Drava levee, a site which has shown a continuous trend of increased water levels in recent years.


Ars Adriatica ◽  
2016 ◽  
pp. 103
Author(s):  
Barbara Španjol-Pandelo

Matteo Moronzon, a member of the Venetian family of woodcarvers, was mentioned for the first time in 1407 according to the present known archival documents. Probably after being trained in his father's workshop in Venice, he moved to Zadar with his family – his wife Francisca and sons Pietro and Francesco. In 1418 he undertook the commission of furnishing carved choir stalls for the cathedral of St. Anastasia in Zadar. Various archival documents testify that Matteo lived and worked in Zadar for many years. Therefore it can be assumed that he probably founded his own workshop in Zadar where his son Francesco was trained too. Apart from the attempt to reconstruct Matteo's life and career, the aim of this paper is to interpret one important woodcarving work of art preserved in situ: choir stalls in the former cathedral of Rab, today the arch parish church of the Assumption of the Blessed Virgin Mary in Rab. Without doubt Matteo was the master carver in the production of the choir stalls in Zadar. Since he lived in Zadar it was not unusual that he had the main role in carving the stalls. In Zadar the selection of motives is more balanced and there are no significant differences in the modelling of decorative elements. However, the question whether Matteo carved absolutely everything or he had assistants arises. Considering the amount of work that had to be done it must be assumed that he had assistants who participated in work and helped him to shape the stalls. However, in literature Matteo was considered the only and undisputed author of the choir stalls in Zadar, mostly because of the preserved document. The analysis of the choir stalls in Rab by Ivo Petricioli as well as their evident formal and stylistic similarities with the stalls from the cathedral in Zadar have led to the general acceptance of the hypothesis that they were carved at the workshop of Matteo Moronzon. However, a comprehensive comparative analysis that could confirm that hypothesis was still missing. The analysis of the details and the whole led to the overall conclusion that there were a huge number of similarities between the choir stalls in Rab and Zadar. Therefore it was concluded that Matteo was the principal designer of the choir stalls in Rab who also carved the best parts in Rab, while others, less successful parts, were made by his apprentices and assistants who at the time lived on the island of Rab. In this respect, if Matteo was accepted as the author of the choir stalls of the cathedral in Zadar he must also be accepted as the author of the choir stalls from the excathedral in Rab.


Author(s):  
J. Aouissi ◽  
Z. L. Chabaane ◽  
S. Benabdallah ◽  
C. Cudennec

Abstract. The impact of changes in agricultural land use and practices as a controlling driver of hydrologic response and as a source of diffuse pollution, are studied in the Joumine River basin, discharging into the Ichkeul Lake, northern Tunisia, a UNESCO World Heritage site since 1979. The lake is characterized by a very specific hydrological functioning based on a seasonal alternation of water levels and salinity through its link to the Mediterranean Sea. Three Landsat images, in situ surveys and SWAT modelling were used to simulate and assess streamflows and nitrate loads under retrospective land uses.


2013 ◽  
Vol 10 (3) ◽  
pp. 2879-2925 ◽  
Author(s):  
R. C. D. Paiva ◽  
W. Collischonn ◽  
M.-P. Bonnet ◽  
L. G. G. de Gonçalves ◽  
S. Calmant ◽  
...  

Abstract. In this work we introduce and evaluate a data assimilation framework for gauged and radar altimetry-based discharge and water levels applied to a large scale hydrologic-hydrodynamic model for stream flow forecasts over the Amazon River basin. We used the process-based hydrological model called MGB-IPH coupled with a river hydrodynamic module using a storage model for floodplains. The Ensemble Kalman Filter technique was used to assimilate information from hundreds of gauging and altimetry stations based on ENVISAT satellite data. Model state variables errors were generated by corrupting precipitation forcing, considering log-normally distributed, time and spatially correlated errors. The EnKF performed well when assimilating in situ discharge, by improving model estimates at the assimilation sites and also transferring information to ungauged rivers reaches. Altimetry data assimilation improves results at a daily basis in terms of water levels and discharges with minor degree, even though radar altimetry data has a low temporal resolution. Sensitivity tests highlighted the importance of the magnitude of the precipitation errors and that of their spatial correlation, while temporal correlation showed to be dispensable. The deterioration of model performance at some unmonitored reaches indicates the need for proper characterization of model errors and spatial localization techniques for hydrological applications. Finally, we evaluated stream flow forecasts for the Amazon basin based on initial conditions produced by the data assimilation scheme and using the ensemble stream flow prediction approach where the model is forced by past meteorological forcings. The resulting forecasts agreed well with the observations and maintained meaningful skill at large rivers even for long lead times, e.g. > 90 days at the Solimões/Amazon main stem. Results encourage the potential of hydrological forecasts at large rivers and/or poorly monitored regions by combining models and remote sensing information.


2017 ◽  
Vol 34 (2) ◽  
pp. 295-307 ◽  
Author(s):  
Kristine M. Larson ◽  
Richard D. Ray ◽  
Simon D. P. Williams

AbstractA standard geodetic GPS receiver and a conventional Aquatrak tide gauge, collocated at Friday Harbor, Washington, are used to assess the quality of 10 years of water levels estimated from GPS sea surface reflections. The GPS results are improved by accounting for (tidal) motion of the reflecting sea surface and for signal propagation delay by the troposphere. The RMS error of individual GPS water level estimates is about 12 cm. Lower water levels are measured slightly more accurately than higher water levels. Forming daily mean sea levels reduces the RMS difference with the tide gauge data to approximately 2 cm. For monthly means, the RMS difference is 1.3 cm. The GPS elevations, of course, can be automatically placed into a well-defined terrestrial reference frame. Ocean tide coefficients, determined from both the GPS and tide gauge data, are in good agreement, with absolute differences below 1 cm for all constituents save K1 and S1. The latter constituent is especially anomalous, probably owing to daily temperature-induced errors in the Aquatrak tide gauge.


1986 ◽  
Vol 52 ◽  
pp. 215-245 ◽  
Author(s):  
M. B. Roberts ◽  
M. R. Bates ◽  
C. Bergman ◽  
A. P. Currant ◽  
J. R. Haynes ◽  
...  

The acheulian site at Boxgrove contains one of the most extensive areas of in situ fauna and flintwork yet discovered in Britain. This material is found in a complex sequence of sediments which represent depositional conditions from a 42 m sea level rise to the onset of a full periglacial climate. Excavation of the archaeological horizon has been accompanied by a programme of multidisciplinary research examining site formation processes, palaeolandscape and palaeoecological development, using sedimentological and environmental reconstruction techniques. Dating of the site is tentative as no absolute dates are available at present. However, comparative analysis with other British sites would suggest a position for the Boxgrove sequence within the Middle Pleistocene. The archaeological horizon is interpreted as being deposited towards the latter part of an interglacial or an interstadial period.


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