Assessment of Salt Water Intrusion from Ponnani to Tavanur along the Banks of River Bharathapuzha in Kerala

Abstract

Groundwater is one of the major sources for irrigation and domestic purposes. The groundwater demand for various purposes is increasing in coastal areas. The population density in the coastal region is high and the health of people depends on the quality of water used. Ponnani, in the Malappuram district, is a thickly populated coastal town of Kerala where the availability of good quality drinking water is lacking. The study was undertaken to analyze the fluctuation of the water table and its effects on salinity intrusion and to understand the suitability of groundwater for drinking and irrigation purposes in the coastal belt of the Tavanur-Ponnani region. Six regions, Tavanur, Nariparambu, Chamaravattom, Purathur, Eswaramangalam and Ponnani are included in the study area. The water level was measured from observation wells in the field at monthly intervals, and samples were collected for water quality analysis during the period 2015 to 2021. The results obtained indicate that there is saline water intrusion in the coastal stretch of Purathur, Padinjarekkara and Ponnani regions of the Bharathapuzha river basin, and both salinity and EC is having an increasing trend in almost all wells during this period. The problem was found to be severe during dry periods (March-May) of the year in the Purathoor and Ponnani regions with salinity and EC rising to about 1800 mg L-1 and 1400 µs cm-1, respectively in the pre-monsoon period, which can be used for drinking only in the absence of an alternate source. In these areas, the groundwater available during the summer months becomes unsuitable even for irrigation purposes. During the monsoon season (June-November), the problem is less severe. Hence, it is recommended to restrict the use of groundwater at least to a lateral distance of 5 km from the seashore along the banks of the river.