Geoökologisches Kolloquium SS 2005

Alle Termine

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Prof. Dr. Madan Jha
Indian Inst. of Technology, Kharagpur und Humboldt-Stipendiat am LS Hydrologie
Donnerstag, 19.05.2005 16:15 H6

Surface Water-Groundwater Interaction: Key to Sustainable Management of Water Resources Systems

Surface water and groundwater ecosystems are linked components of a hydrologic continuum leading to related sustainability issues. The interactions between surface water and groundwater are highly complex in nature. The research activities in this area have proliferated during the 1990s, with a major focus on hydrological and biogeochemical processes. However, a broader perspective of such interactions is required to better understand the intricate processes involved, which in turn can ensure sustainable water resources management.

Adequate knowledge of aquifer parameters is of utmost importance for the efficient management of groundwater basins. There are many methods for finding out aquifer parameters such as the pumping test data analysis, grain-size analysis, floodwave-response technique, tidal response technique, and numerical modeling. Under suitable field conditions, it is possible to calculate the hydraulic diffusivity (ratio of aquifer transmissivity to storage coefficient) of an aquifer system by analyzing its response to river stage fluctuations, which is known as the floodwave-response technique. A field study was carried out in the Konan groundwater basin of Kochi Prefecture, Japan to investigate the river-aquifer interaction process. Using the field-observed hydrogeologic data and the river-stage data of a perennial river system, an inverse-modeling analysis was performed to explore the practicability and reliability of the floodwave-response technique (also known as ±river-aquifer interaction technique²) in estimating the hydraulic parameters of the Konan aquifer. The analysis of the pertinent hydrologic and hydrogeologic data revealed a strong relationship between the river stage and the groundwater levels over a major portion of the basin. Based on this finding, suitable river hydrographs and well hydrographs were selected for the aquifer parameter estimation using the floodwave-response model. The results of inverse modeling indicated high values of aquifer diffusivity at 4 sites ranging from 16 to 194 m2/s. However, the overall average aquifer diffusivity was found to be reasonable (0.7-3.5 m2/s). All the selected flood events were not found suitable for determining reasonable values of hydraulic diffusivity at individual sites. Furthermore, using the optimal diffusivities at two sites and the aquifer transmissivity from the pumping tests at these sites, the storage coefficient values were estimated as those of truly confined aquifers. In contrast, reasonable values of storage coefficient were obtained based on the average diffusivity estimates. A sensitivity analysis of the floodwave-response model indicated that the optimal hydraulic diffusivity is very sensitive to the distance parameters of the model. It is concluded that a judicious application of the floodwave-response technique is essential for obtaining reliable estimates of hydraulic diffusivity, particularly in the case of phreatic aquifer systems.


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