Hydrochemical characterisation and identification of seawater intrusion in the Visakhapatnam coastal aquifer.

Groundwater dependency has increased due to several factors like population increase, industrialization, and climate change impact. Analysis of groundwater is important to know the present status and also for better management of natural resources. Groundwater samples from 41 locations were collected along the study area during the pre and post-monsoon seasons, and samples were analysed for pH, EC, total dissolved solids (TDS), major cations, and anions like Ca2+, Mg2+, Na+, K+, Cl-, HCO3- and SO42-. From the chemical analysis results, seawater intrusion is identified through qualitative approaches, i.e., Simson ratio (Cl/(HCO3 + CO3) and Na/Cl ratio. Simson ratio ranges between 0.316 to 2.119 during pre-monsoon and 0.124 to 3.947 during post-monsoon, and from Na/Cl ratio, 30 samples fell under seawater intrusion during pre-monsoon and 38 samples during post-monsoon. The Simpson ratio results also show that seawater intrusion is reducing during the post-monsoon due to increasing groundwater levels caused by rains. From the water quality index classification, 4.88% of the water samples fell under excellent in both seasons, and the rest of the samples were all in the remaining four classes. The spatial analysis was also done to understand the changes in groundwater quality and seawater intrusion over space.

Evaluation of the geomorphological scenario of Shimsha River Basin, Karnataka, India.

Drainage morphometric analysis is very substantial in determining the characteristics of a river basin. It is performed through spatial analysis, which helps study the various hydrological interactions and responses in the watershed. In this research, the authors have tried to study the geomorphological scenario of the Shimsha River basin using the remote sensed data, toposheets, and geographic information systems tools. In the current study, linear, aerial, and relief parameters are derived and analysed to evaluate the runoff and erosion characteristics of the basin. The stream pattern of the Shimsha River is mostly dendritic with a sixth-order stream and a drainage density of 0.56 km/km2. According to the morphometric characteristics, the study area appears to be in the equilibrium stage of development, slightly elongated, with moderate to low flow rates and reduced sensitivity to erosion. The hypsometric curve and hypsometric integral value of the Shimsha River basin show the mature phase of the geomorphic evolution of the basin and imply that runoff will be moderate to high. The asymmetry factor of the Shimsha River basin is 49.3, which specifies that the basin is slightly tilted towards the right. The study's results clarify the phenomena of runoff and erosion, which is crucial for watershed management initiatives.

Spatiotemporal Rainfall Variability and Trend Analysis of Shimsha River Basin, India.

Karnataka state has the second highest rainfed agricultural land in India, where agricultural output relies heavily on rainfall. The Shimsha basin, a sub-basin of Cauvery in the state, comes under a semi-arid region and predominantly consists of rainfed agricultural land. Rainfall patterns have changed dramatically with time resulting in frequent floods and droughts. Understanding the spatiotemporal distribution of rainfall and its change patterns in the area would benefit sustainable agriculture planning and water resources management practices. The current study aims to determine the variability and trend in rainfall. The daily rainfall data of the Shimsha basin from 1989 to 2018 is collected, and the annual, seasonal, and monthly rainfall totals and the number of rainy days are derived. All the time series are subjected to statistical methods to examine rainfall variability and trend. The mean, standard deviation, coefficient of variation (CV), and Standardized Anomaly Index are used for the preliminary and variability analysis, while the coefficient of skewness and kurtosis are used to understand the rainfall distribution characteristics. The homogenous and serially independent series are identified by homogeneity and serial correlation tests. The trend in the homogenous and serially independent series is identified by Mann-Kendall and Spearman's rank correlation tests, while the magnitude of the trend is quantified using the Sen's slope technique, and the trend change point is evaluated using the sequential Mann-Kendall test. Based on the study, the average rainfall in the study area is 801.86 mm, with CV ranging from 43.3 to 22.27%. The southwest monsoon (SWM) season brings the greatest rain to the basin, followed by the post-monsoon (PM), summer, and winter seasons. In the annual time frame, except one station, all other stations have shown significant or insignificant increasing trends. The seasonal rainfall has shown insignificant rising trends during the summer and winter seasons while insignificant increasing and decreasing trends during the PM season. The SWM season has indicated significant increasing trends, insignificant increasing and decreasing trends. Overall, the study area has noticed an increased annual and seasonal rainfall except for the post-monsoon season, during which the rainfall showed a considerable decline. The findings of the study are helpful in water resource management, agricultural planning, and socioeconomic development in the study area.