Study and application of Remote Sensing techniques
for groundwater investigation:
Case-study of coastal
zones of Red River and Mekong River deltaic plains
of Vietnam
Nguyen Kim Minh Cong
Center of Geography and Natural Resources,
NCSR of Vietnam
Objectives and scope
The Coastal Zones chosen for the Studies are located in the Northern and Southern Vietnam respectively, that have a lot of differences not only on the geological, geomorphologic building-up also in the physico-geographical and meteoro-climatic characteristics.
Under the new socio-economic strategy of the Government of Vietnam, these areas are subjected to a period of intensified economic development and immense investment. Thus, the problem of detailed assessment of the Natural Conditions of the Areas has been raised and required a timely resolution. Consequently, the project RAS/86/141 named : "Application of Remote Sensing Techniques for the Study and Assessment of Natural Conditions, natural Resources and Development Dynamics of the coastal Zones of the Red River and the Mocking River Deltas" had been established and been sponsored and founded by ESCAP Organization.
Considering the potentials of Remote Sensing Techniques, the Directorate of the Project had entrusted the Staff of Geologists, Hydro geologists and Geomorphologies of the :Remote Sensing Application Division' of NCSR of Vietnam a subproject for Hydro geological Interpretations of the Lands at and Spot data for the aims of preparation of Hydro geological maps for the Study Areas.
The significant contributions of the Hydro geological Inter-pretations are supposed to be observed concerned mapping Regional geological features ane Tectonic domains that because of their colossal size and obscure ness under the soil-and vegetation-cover up-to-now stayed unmapped. The mapping of them will be very a significant input for study of the hydro-geological conditions and their re-assessment.
However, owing to the Scale of the Studies, and the inherent resolutions of the lands at and Spot imageries, the scope of the Hydro-geological Interpretations is expected to be limited, since only the Regional Structures, broad litho logic Groups and Macro-landforms, and thus, the main hydro geological nits can be identified.
Choice of materials and methodology
The basic data to be used for the Subproject "Hydro geological interpretations' has been the lands at MSS imageries (Black and White prints, available in a series from 1984to 19880 and the Spot FCC imageries, 9taken in February 1987) on the scale of 11/2500,000.
The following are considered as favorable environmental conditions for carrying out investigations ; 1) period of clean atmosphere and least vegetation cover : 20 Period of intensive development of groundwater natural phenomena and processes: 3) Period of calm sea surface. Hence, the mages taken during the dry season have been chosen for the interpretation work.
The data suitable for the investigations have been analyzed by visual interpretation techniques only. Due to the lack of possibility, the Advanced Computer Processing. Techniques such as supervised Classification, Bank-Rationing and Contrast Enhancement have not been conducted.
During the Interpretation Course, a significant supplementary information has been gained based on the Visual interpretations of the Lands at and Spot Films conducted on the Additive-Color Viewer (aC-90).
Annotation of various Strati graphic Units, Litho logic Groups and Hydro geologic Units has been taken from the Published and Archived Geological Literature and Maps complied by the "General Department of Geology and Mining of Vietnam".
Geological Information from the former conventional. On-ground investigations on Geology, Geomorphology and Groundwater has been generalized and evaluated and then used in term of the ground-truth information for checking the interpretation results.
Since the Areas were studied in details in the Geological Relations, the Ground Geological information has been collected and read by the Interpreters so that an adequate knowledge on Geology, Geomorphology and Groundwater has been provided to them prior to the Preliminary interpretation has been conducted independently, without special reference to the Ground information. only on the Final interpretation stage, the preliminary interpretation results have been revised wherever it was necessary according to the Ground information.
