Characterizing the vadose zone and a perched aquifer near the Vosges ridge at the La Soutte experimental site,Obernai, France

We consider a series of hydrogeophysical techniques that provide a multiscale investigation of the water content in the vadose zone and of the perched aquifer at the experimental site of “La Soutte” in the Vosges Mountains (France). It is located in a catchment area where several springs and streams occur along fractured volcanic and weathered plutonic rocks. The site is the object of a long-term study that uses both continuous and repeated measurements to monitor hydrogeological processes. The main results from AMT and DC resistivity techniques allow the determination of a high-resolution 3D resistivity model over a large range of depths (from 10⁰ to 10³ m). We discuss their use and propose a hydrogeological model (porosity, water conductivity and water content). We also use MRS and GPR for a detailed investigation of the shallow part of the catchment that consists of soil and weathered rocks of highly varying thickness (0 to 15 m). MRS is used to map the thickness and total water volume content by unit surface of the saturated weathered zone. It also yields estimates of the vadose zone thickness through the depth to the top of the saturated zone. Moreover, we show results from GPR CMP measurements that yield estimates of the water content and porosity in the shallowest layer (0–30 cm) by simple interpretation of the ground direct wave.     

Groundwater investigation on sand dunes area in southern part of Vietnam by magnetic resonance sounding

In the last five years, magnetic resonance sounding (MRS), as a non-invasive geophysical method, has emerged as a new technique for ground water investigation in Vietnam. In this paper, we present the general theoretical basis of this method together with acquisition, processing, and interpretation of the MRS data. We show a case study of MRS surveys in sand dunes area in order to characterize aquifers situated in the southern part of Vietnam. From the interpretation of MRS soundings we delimited an aquifer layer in the subsurface with strong lateral variations for which we determined the depth at 44 m and water content between 3% and 9.5%. The longitudinal relaxation constant T*₁ is about 250 m s, while the transverse relaxation T*₂ is between 150–200 m s. That indicates fine to medium grain size and thus low to medium hydraulic permeability. These results are confirmed by the observations from the well LK1 between 45 to 70 m. The results of other MRS measurements showed the presence of a low water bearing aquifer and were confirmed by the observations in two other wells.     

Comparative study of body composition of different fish species from brackish water pond

Seven species of fish (Catla catla, Cirrhinus mrigala, Cyprinus carpio, Hypophthalmicthys molitrix, Labeo rohita, Mori-Rahu Hybrid and Thalla-Rahu Hybrid) were collected from a brackish water pond near Muzaffargarh, Pakistan for the comparison of body composition. All the seven species were found relatively well adapted to the saline environment though some of them showed significant differences in body composition. Results obtained did not show any adverse effect of salinity on these fish species. The mean values of body constituents, except for protein content (dry and wet body weight) differed significantly (P<0.05) among various fish species. Minimum amount of water content and maximum amount of lipids, organic content and condition factor were observed in Cyprinus carpio indicating that Cyprinus carpio show overall better growth in brackish water as compared to other species. Cyprinus carpio may be recommended for culturing in such water bodies and farmers may be encouraged to farm this species on mass scale.