Water quality is the critical environmental determinant that influences the agricultural production and therefore, the economy that solely depends on its agricultural productions. Batiaghata Upazilla is one of the major crop productive areas of Khulna region and the agricultural production here largely depends on the natural water of the Shailmari River system around it. The present study was conducted to assess the suitability of this coastal river water for irrigational use. 66 water samples were collected during this study in three consecutive agricultural seasons, viz., pre-monsoon (22), monsoon (22) and post-monsoon (22) from 11 sampling stations within the river system considering the high (11) and ebb (11) tides for each station. Standard methods were followed throughout the study period for the collection of the samples and analysis of major physicochemical parameters (pH, EC, TDS, salinity, Na, K, Ca, Mg, Cl, HCO 3 , SO 4 , NO 3 and PO 4 ). Hydrocehmical characterization using Piper trilinear diagram shows that the water of the river system is Na-Cl dominated saline water type in pre-monsoon, whilst most of the samples of the river and the connected channel are characterized as fresh water of Ca-Mg-Na-HCO 3 and Ca-Na-Mg-HCO 3 types in monsoon and post-monsoon respectively. The calculated values of chemical indices like SAR, %Na, KI, PI and MH using the results of the analysed parameters indicate that the river water is chemically unsuitable for use in irrigation during pre-monsoon, while in the monsoon and post-monsoon the river water is within good to permissible limit for the use in the agricultural fields. However,

Surface water has become one of the most vulnerable resources on the earth due to deterioration of its quality from diverse sources of pollution. Understanding of the spatiotemporal distribution of pollutants and identification of the sources in the river systems is a prerequisite for the protection and sustainable utilization of the water resources. Multivariate statistical techniques such as Principal Component Analysis (PCA) and Factor Analysis (FA) were applied in this study to investigate the temporal and spatial variations of water quality and appoint the major factors of pollution in the Shailmari River system. Water quality data for 14 physicochemical parameters from 11 monitoring sites over the year of 2014 in three sampling seasons were collected and analyzed for this study. Kruskal-Wallis test showed significant (p < 0.01) temporal and spatial variations in all of the water quality parameters of the river water. Principal component analysis (PCA) allowed extracting the contributing parameters affecting the seasonal water quality in the river system. Scatter plots of the PCs showed the tidal and spatial variation within river system and identified parameters controlling the behavior in each case. Factor analysis (FA) further reduced the data and extracted factors which are significantly responsible for water quality variation in the river. The results indicate that the parameters controlling the water quality in different seasons are related with salinity, anthropogenic pollution (sewage disposal, effluents) and agricultural runoff in pre-monsoon; precipitation induced surface runoff in monsoon; and erosion, oxidation or organic pollution (point and non-point 2 sources) in post-monsoon. Therefore, the study reveals the applicability and usefulness of the multivariate statistical methods in assessing water quality of river by identifying the potential environmental factors controlling the water quality in different seasons which might help to better understand, monitor and manage the quality of the water resources.

At Shailmari River basin, located in the central Ganges Delta and the southwestern coastal Bangladesh, groundwater is the only potable source for water supply due to incompatible surface water sources. However, salinity degradation along with arsenic and iron contamination poses a serious health threat to the basin community. Considering this, an investigation was carried out along both banks of the river to assess groundwater vulnerability and its quality for drinking by conducting multi-seasonal water sampling campaigns from 20 domestic wells and analyses (both in-situ and laboratory) for several physico-chemical (pH, EC, TDS and major ions) and biological (coliforms) parameters. The results show slightly alkaline groundwater in the study area with largely variable chemical composition, i.e. EC varies from around 1900 to 2700 µS/cm. The abundance of major ions indicates as Na + > Ca 2+ > Mg 2+ > K + for cations and 3 HCO − > Cl − > 2 4 SO − > 3 NO − > 3 4 PO − for anions. As per the Canadian water quality index (CCMEWQI), almost all groundwater samples concentrate in the marginal category meaning that groundwater is frequently threatened. Besides, it is not fully safe for drinking as revealed from comparison of geochemical data with national and WHO water quality standards.

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