**5. Conclusion**

32 Novel Approaches and Their Applications in Risk Assessment

The evolution of the daily CdP flux in the section of the Charente River was compared to that of the corresponding SPM flux. This comparison revealed a good statistical relationship between both parameters (Figure 7B). Based on this relationship, we can define a CdP average of ~2.90 mg/kg, corresponding to the regression slope and, probably, to the CdP level in agricultural lands which are mechanical eroded during runoff. Based on this, we have detected a small increase in CdP that was not due to the contribution of SPM at the CHA4 site and a strong CdP anomaly at the CHA10 site. Like for CdD, the minor CdP anomaly in CHA4 probably results from the presence of formerly exploited mineral deposits (Ba-Pb-Zn mineralization). Between the CHA9 and CHA10 sites, we have observed a SPM decrease related to sedimentation inducing decreasing SPM fluxes ('loss') in this section. Based on the observed relationship between SPM flux and CdP flux in the Charente River, the expected CdP flux at the Chaniers site for an instantaneous SPM flux of 71 t/d would be ~200 g/d (Figure 7B). The observed CdP flux of 353 g/d being ~1.8 times higher (Table 2) clearly suggests a significant Cd enrichment in SPM due to anthropogenic sources and

reflects observations made for CdD.

0 25 50 75 100 **Qj (m3/s)**

0

0 25 50 75 100 **SPM flux (t/d)**

100

200

**Cdpart flux (g/d)**

Fig. 7. Relationship between daily dissolved Cd flux and water discharge (A) and between daily particulate Cd flux and SPM flux (B) at strategic sites in the main channel of the

The dissolved and particulate flux estimates underline the Cd partitioning (i.e chemical form) in the Charente River system. In the main section of the Charente River, the instantaneous Cd flux was mainly due to SPM transport (reaching 80% at CHA10), except at CHA2 (downstream from the Lavaud Reservoir) and in the Moulde River (upstream and downstream part), where the particulate transport contributed 47%, 45% and 40%, respectively, to total (dissolved + particulate) Cd (CdT) fluxes. These results suggest that the particulate phase is the predominant Cd vector in the Charente River system and demonstrate that efficient reduction of Cd transport into the Marennes-Oleron Bay would

By extrapolating daily fluxes to the annual scale, we have obtained a first approximation of annual SPM and Cd exports to the Charente Estuary and in fine to the MOB. These estimates probably represent the orders of magnitude, although errors on flux estimates

imply limitation of mechanical erosion, mainly in the agricultural areas.

**B**

300

400

0

Charente River

20

40

60

**Cddiss flux (g/d)**

**A**

80

100

This study represents a major advance in the geochemical characterization of water and water-borne particles in the Charente River and contributes to a better understanding of the Cd transfer into the Marennes-Oleron Bay. The main results obtained have allowed to:


In terms of perspectives, further work should be carried out during low water because of the strong relationship between water quality and hydrology. It would also be necessary to determine more precisely the origins of the observed Cd anomaly, by taking samples from the former mining deposit and agricultural soils. This approach should be completed by a longitudinal sampling profile between CHA9 and CHA10, where significant additional dissolved and particulate Cd fluxes occurred. Our study includes the Charente River upstream from the Chaniers site, which is considered as the outlet of the fluvial system. Furthermore, a more complete mass balance should include fluxes via two other major tributaries, the Boutonne and Arnoult Rivers, entering the Charente Estuary in the tidal reaches.

Spatial Cadmium Distribution in the Charente Watershed and

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**6. References** 


**3** 

*Germany* 

**Planning and Decision Support** 

**Resources Management (IWRM) on** 

Björn Zindler, Andreas Borgmann, Sandra Greassidis, Sylvia Jaschinski, Christian Jolk and Harro Stolpe

**River Basin Level in the Southeast-Asian** 

**Region on the Example of Vietnam – Tools for** 

**Water Quantity and Quality Risk Assessment** 

*Ruhr University Bochum, eE+E Environmental Engineering and Environment* 

A lot of countries worldwide suffer from emerging water related problems. Droughts, floods and water contamination are the most pressing issues. According to the United Nations (UN, 2008), in 2008 over 880 million people of the developing world's population were without access to safe drinking water and over 2.5 billion lacked adequate sanitation. Considering a rapid global change driven by climate, land use and demographic changes, one of the most important tasks of the global community is to find means of using and protecting natural resources in a responsible way in order to support a holistic and sustainable development. The integrated approaches of the international R&D projects funded by the German Federal Ministry of Education and Research (BMBF) are helping to

One specific program in this framework is called "Integrated Water Resources Management" (IWRM). The primary focus of the program is to establish cooperation between science, administration and economy between Germany and foreign countries. The R&D projects in the program should develop management concepts and implement action plans in the water sector in cooperation with partners of the project regions. Another task is the contribution of adapted water related technologies and the transfer of know-how.

Vietnam is one of the model regions of the funding program. Since 2007, the German-Vietnamese joint R&D project Integrated Water Resources Management in Vietnam (IWRM-Vietnam) funded by the BMBF is developing methods and technologies adapted to

The institute of Environmental Engineering and Ecology (eE+E) at the Ruhr University Bochum (Prof. Dr. Harro Stolpe) coordinates the R&D project IWRM-Vietnam and

understand, interpret and solve problems in the water sector.

**1. Introduction** 

Vietnamese conditions.

**Tools for Integrated Water** 

