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Conference Agenda

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Session Overview
Session
C2: ID.10664 Yangtze River Basin Hydrology
Time:
Tuesday, 05/Jul/2016:
5:30pm - 6:30pm

Session Chair: Massimo Menenti
Session Chair: Chang-Qing Ke
Workshop: Hydrology & Cryosphere
Location: Building 7-220#, School of Resources and Environmental Science, Wuhan University

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Presentations
Oral presentation

Satellite data and hydrological model to asses water quantity and quality in the Yangtze river basin

Marco Mancini1, Jiren Li2, Chiara Corbari1, Jingfeng Xin2, Jianli Zhang2, Xingnan Zhang3, Bob Su4, Hervè Jesou5

1politecnico di Milano, Italy; 2IWHR, China; 3Hoai University, China; 4University of Twente, The Netherlands; 5Sertit, France;

Water quantity analyses are assed with the support of the fully distributed hydrological model FEST-EWB. The model algorithm solves the system of energy and mass balances in terms of a ground representative equilibrium temperature (RET), that is the land surface temperature that closes the energy balance equation and so governs the fluxes of energy and mass over the basin domain. This temperature, which is a model state variable, is comparable to LST as retrieved from operational remote sensing data (MODIS) permitting the model control also from RS data.

The model simulations allows to quantify the effects of water balance on the river discharges for several river cross section from upstream to the estuarine. Flow duration curves are then provided for the four available gauges stations where model simulation are compared with observed data. The effect of Three Gorges dam is also considered in the model simulations. this represents also the dynamic of the three large lakes (Poyang, Dongting and Taihu), which change considerably their surface according with the dry and Monsoon seasons. Lakes dynamic is also monitored from satellite using MERIS and ASAR data to infer surface area changes and LEGOS altimetry data (Topex/Poseidon, Jason, ENVISAT) for water level.

FEST-EWB is run in for the whole Yangtze River basin at spatial resolution of 0.05° and temporal resolution of 3 hours. Results are provided in terms of hourly evapotranspiration, soil moisture and land surface temperature maps for the period between 2003 to 2006 and flood hydrographs at different river cross sections.

Water quality analyses are performed along the Yangtze river estimating turbidity and suspended solid sediments from MERIS (250 m) and MODIS (300 m) data using different literature algorithms. Two main results are shown: i) the seasonal and yearly variations of turbidity and suspended soil and their correlations between river discharges and precipitation events; ii) the quantification of the effect of Three Gorges dam the suspended sediment transport downstream.

The years 2002, 2004 and 2006 were selected as particular periods: the first one is before the Three Gorges Reservoir impoundment, the second one is characterized by severe floods, while the last one is a dry year.


Poster

Remotely sensed land surface temperature, lakes area and water level, and ground discharge for hydrological model calibration in the Yangtze river basin

Chiara Corbari1, Marco Mancini1, Hervè Jesou2

1Politecnico di Milano, Italy; 2Sertit, France;

The main objective is to improve the estimate of water balance processes in the Yangtze river in China using in a synergic and innovative way remote sensing data and distributed hydrological model.

In particular, distributed hydrological models of energy and mass balance usually need in input many soil and vegetation parameters, which are usually difficult to define. This work tries to approach this problem performing a parameters calibration based on remote sensing land surface temperature data (LST) as a complementary method to the traditional calibration with ground data. A pixel to pixel calibration procedure of soil hydraulic and vegetation parameters for each pixel of the domain is proposed according to the comparison between observed and simulated land surface temperature.

A distributed hydrological energy water balance model (FEST-EWB - Flash–flood Event–based Spatially–distributed rainfall–runoff Transformation- Energy Water Balance), that solves the system of energy and mass balance equations as a function of the representative equilibrium temperature (RET) will be used. RET is comparable to the land surface temperature as retrieved from operational remote sensing data. This equilibrium surface temperature, which is a critical model state variable, is compared to land surface temperature from MODIS.

A similar calibration procedure will also be applied performing the traditional calibration using only discharge measurements at different available control cross sections.

The dynamic of the three large lakes (Poyang, Dongting), which change considerably their area during the seasons, will also be analyzed using MERIS and ASAR data to infer surface area changes and LEGOS altimetry data (Topex/Poseidon, Jason, ENVISAT) for water level. The FEST-EWB hydrological model is then calibrated and validated against water level data, while lake area changes are used as input data.

FEST-EWB is run in for the whole Yangtze River basin at spatial resolution of 0.05° and temporal resolution of 3 hours. Results are provided in terms of hourly evapotranspiration, soil moisture and land surface temperature maps for the period between 2003 to 2006 and flood hydrographs at different river cross sections.


Poster

Retrieval of suspended solids sediment and turbidity from MODIS and MERIS imageries along the Yangtze river in the Three Gorges Dam Area

Antonio Di trapani, Chiara Corbari, Marco Mancini

Politecnico di Milano, Italy;

The aim of this study is to estimate water quality parameters along the Yangtze river in the Three Gorges Dam area quantifying turbidity and suspended solid sediments retrieved by remote sensing data testing different algorithms. In particular, the main idea is to evaluate seasonal and yearly variations of turbidity and suspended solids and hence, their correlations to river discharges and precipitation events.

These analyses are also performed to quantify the effect of Three Gorges dam and how its flow regulation affects the sediment transport downstream.

The years 2002, 2004 and 2006 were selected as particular periods: the first one is before the Three Gorges Reservoir impoundment, the second one is characterized by severe floods, while the last one is a dry year.

Due to the lack of ground data in correspondence of satellite overpasses, it was impossible to calibrate new algorithms. Different literature algorithms have been selected, applying the most suitable to retrieve suspended solid sediment and turbidity in the selected river.

Remote sensing reflectance from MODIS - MOD09GQ (pixel size 250x250 m) and MERIS FR L2 (pixel size 300x300m) are used.

Linear correlations between the retrieved values from satellite imagery and discharges are obtained for the three analyzed years with high value of the coefficient of determination. Moreover, the results highlight that sediment transport in Yangtze River is affected by the Three Gorges dam’s flow regulation showing that both turbidity and suspended solids retrieved values have two distinct trends before and after the reservoir impoundment.

Finally, monthly and yearly satellite estimates of suspended solid sediment are computed based on the found correlation with observed ground discharges, in order to be compared with literature values. A general good agreement is obtained, but with differences among the different algorithms which tend to underestimate or overestimate especially pick values.



 
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