Assessment of water quality parameters due to longitudinal salinity inundation at Indus Delta: a case study of Kharo Chan, District Sujawal

Abstract

Deltas are landforms that are formed at the regions where a river meets an ocean. When the freshwater of a river joins the saline water of an ocean, a transitional state of water is obtained. This zone of transition varies on the quantity of freshwater entering the ocean and the quality of both waters. Indus River is facing severe challenges due to climate change which has resulted in reduced water flow in the river. Consequently, seawater intrusion takes place which causes coastal erosion, stunted mangrove growth, and the narrowing of the river towards the seaside. The groundwater in the deltaic regions is unfit for drinking which forces an increased reliance on surface water. Sindh Province of Pakistan, particularly the coastal regions, suffers from severe water quality problems, affecting approximately 41% of the population. The population of this region is deprived of good-quality water for their daily use. This research aims to evaluate the physiochemical parameters of water in the Indus River to identify the zone of salinity inundation and determine safe zones for accessing surface water in the Indus Delta in the Sujawal district. Water samples were collected from Khobar Creek, ending in the Arabian Sea in the areas of Shah Bandar and Kharo Chan at an approximate interval of 5 km. These samples were analyzed for various physical and chemical properties. Properties were compared spatially to develop a relationship between distance and quality of water. Results indicate that the values of dissolved solids in collected samples are between 21,450 and 900 mg/L, pH was between 6.66 and 7.63, conductivity of the samples varied from 33,000 to 1385 µS/cm, acidity values were between 921.14 and 399.84 mg/L, hardness was in the range of 3654 to 192 mg/L, and the turbidity was in between 21 and57 NTU. It was revealed from the results that seawater is having a severe influence upto 15 km from the mouth of the creek in which not a single parameter except the pH was complying with WHO recommendations. In the interval of 15 to 30 km, some properties of water were complying with WHO recommendations, while some of them were deviating from the limits. It has been concluded that turbidity was improving while going toward the ocean, while Total Dissolved Solids, hardness, and chloride concentrations were increasing as water was getting closer to the sea while pH was found almost unaffected. The findings emphasize the need for addressing environmental degradation, social hardships, and economic challenges caused by these water quality issues. Ultimately, the quality of water is crucial for various activities specifically for drinking purposes, and its suitability for specific purposes is of utmost importance.