DIFFUSIVITY OF AN ' AQUIFER IN BETWA BASIN (M.P.) BY FLOOD WAVE RESPONSE TECHNIQUE

Abstract

Generally it is very difficult to obtain reliable and representative specific yield/storage coefficient values from field tests especially for an unconfined aquifer.. The hydraulic situation near the streams that links the streamflow with the aquifer parameters is quite complex and is not fully understood and needs-.detailed study. For any aquifer an important parameter is diffusivity which is defined as the ratio of transmissivity and storage coeffi-.cient., Diffusivity can be determined based on the recession of the baseflow in the stream. The diffusivity of a homo-geneous isotropic aquifer can also be determined from the response in the aquifer to fluctuations in river stage. Observed changes in the head in the aquifer are compared with theoretical values of head computed assuming a series of values of diffusivity. Based on these two basic approaches the diffusivity of the aquifer has been evaluated by several methods and the results are presented and discussed. The data generated from the ground water level and river stage hydrographs available for Kuakheri site on Nion river which is a tributory of Detwa river in Madhya Pradesh ( India) has been made use of this study. The value of aquifer diffusivity calculated from stream flow recession curves adopting the method of Singh and Stall (1971) is 11.5 x 105 m2/day where as Werner and Sundquist (1951) solution based on the water table recession curve gives the . value of 1.0 x 10 m2/day. The diffusivity has also been estimated from water level fluctuations induced by rise/fall in stream stage adopting the methods of Edelman (1947),Carslaw and Jaeger (1959) and Finder (1969) . In case the last two methods, a computer program has been developed for determin-ation of diffusivity. The values obtained by these methods ranged from 33 to 7.4 x 103 m2/day. Diffusivity values determined from flood response model analysis are found to be close to the field values of diffusivity estimated from pumping test analysis in the area, indicating that flood wave response model used in this study gave reasonable values of diffusivity of the aquifer in the study area. The aquifer characteristics calculated by flood wave response method is relatively inexpansive and are reliable for an aquifer that is hydraulically connected to a stream or river.