CS(AR)-12/96-97 : Identification of sampling sites for water quality monitoring in Narmada basin (M.P.)

Abstract

Assessment of water quality conditions over a wide area with respect to time and space requires the monitoring activities to be carried out in a network. The location of a permanent sampling station is probably the most critical factor in a monitoring network which collects water quality data. If the samples collected are not representative of the water mass, the frequency of sampling as well as the mode of data interpretation and presentation becomes inconsequential.

Besides the economic considerations there are three levels of design criteria of sampling station location. The macrolocation deals with river reaches in the river basin, the microlocation deals with the location of outfalls or other specific features within a river reach and the third level deals with the representative location points within a river's cross section. The Sharp's procedure which is widely used for selecting locations is used for locating sampling points in the Narmada river basin.

The sequential water sampling sites were identified in the search for a pollution source using four different criteria’s e.g. tributaries, BOD, NPR and Pesticides. Only four levels of hierarchy have been used in the study. However, it was found that for the detection of single pollution source, sampling stations of the seventh level of hierarchies should be used.

Each of the four networks presented namely tributary, BOD, NPK, and pesticides based differs somewhat but it share a common approach towards the selection of reaches in which to sample. It must be emphasized that locations of sampling stations determined are not to be strictly applied. Therefore, an engineering judgement is required to locate a monitoring site which satisfy most of the technical requirements while minimizing the financial requirements. It is suggested that the proposed monitoring network may be used as guidelines in pin-pointing the appropriate sampling sites.

Further, it is observed that the present monitoring sites being monitored under GEMS/MINARS are self-sufficient as far as the middle and upper basin is concerned. But it certainly needs improvement in the downstream portion of the basin particularly for controlling the pesticides, nutrient related problems in the lower basin having very high pollution loadings of pesticides and NPK.