This study examines the spatio-temporal variation in the stable isotopic composition of oxygen (δ¹⁸O) and hydrogen (δD) in groundwater from alluvial and lateritic aquifers in Northern Kerala, India, in relation to seasonal rainfall patterns and hydrogeological settings. The isotopic composition of rainwater in the study area exhibits higher variability during the monsoon seasons, attributed to the influence of cyclonic activity and isotopic fractionation during precipitation events. Groundwater in both alluvial and lateritic aquifers of the study area exhibits distinct seasonal variations in δ¹⁸O and δD values between pre-monsoon and post-monsoon periods, reflecting a shift from evaporation-influenced conditions during the pre-monsoon to dominant meteoric recharge in the post-monsoon season. Negative isotopic separation (Δδ) values and regression characteristics indicate that Southwest Monsoon (SWM) rainfall is the primary source of groundwater recharge, with post-monsoon depletion reflecting seasonal mixing rather than dominant North East Monsoon (NEM) influence. Deuterium excess in groundwater serves as an effective proxy for recharge dynamics, and its relationship with Total Dissolved Solids (TDS) highlights the influence of infiltration rates, evaporation intensity, and aquifer permeability on groundwater recharge processes. A mass balance approach estimates that rainwater contributes 35.7
The study examines at how accurately multiple reanalysis and satellite-based precipitation datasets represent actual precipitation across Kerala, an Indian coastal state. The IMD gridded rainfall data was used as the reference dataset for comparative analysis. Eight datasets including IMERG (Early Run, Late Run and Final Run), CMORPH CDR, CDR, PDIR, PERSIANN and CCS data products were analyzed for the 21-year period from 2003 to 2023. Four statistical techniques were used to evaluate the performance of these dataset. These techniques include the correlation coefficient, root mean square error (RMSE), mean error (ME) and relative bias (RB). The results show that the IMERG Final Run dataset performs better, especially in regions with heavy rainfall like the Western Ghats. On the other hand, datasets such as PDIR, PERSIANN and CCS tend to underestimate rainfall and show weaker correlation with the IMD gridded data especially in hilly areas. The results illustrates the importance of choosing correct dataset for accurate rainfall analysis which can be used for hydrological and climate studies in complex coastal regions.
Water stress significantly influences the physiological functioning and productivity of medicinal plants, necessitating reliable indicators for early stress detection and efficient irrigation management. This study evaluated leaf temperature and the Crop Water Stress Index (CWSI) as indicators of physiological responses and irrigation requirements in selected high-value medicinal plants grown under irrigated and non-irrigated conditions in Kerala, India. Key parameters assessed included stomatal conductance, transpiration rate, photosynthesis rate, foliage temperature, and CWSI under irrigated and non-irrigated conditions. Infrared thermometry was employed to quantify canopy–air temperature differentials associated with transpiration dynamics and plant water status. The results demonstrated clear diurnal variations in foliage temperature corresponding to changes in transpiration and atmospheric conditions. Non-irrigated plants exhibited substantially higher CWSI values (0.6–0.8) compared with irrigated plants (0.3–0.5), indicating greater water stress severity. Significant correlations were observed between CWSI and leaf photosynthetic rate (r2 = 0.49–0.79, P < 0.001), while the stomatal conductance-based index showed strong agreement with measured stomatal conductance (r2 = 0.52–0.87, P < 0.001). Water deficit induced stomatal closure, reduced transpiration and photosynthetic activity, increased leaf temperature, and altered plant water relations. The findings demonstrate that leaf temperature and CWSI are robust, rapid, and non-destructive indicators of plant water status and provide a practical framework for precision irrigation scheduling in medicinal plant cultivation. Integrating thermal sensing with physiological monitoring can improve irrigation efficiency, optimize water use, and enhance climate-resilient management of medicinal crops.
Abstract Understanding the precise spatiotemporal movements of rainfall and its relationship with streamflow moment is crucial for effective water resource management in the Western Ghats region, particularly in the Chaliyar basin where extreme events have increased, resulting in repetitive disasters. To investigate the impact of rainfall variations on stream flow discharge in the basin, it is necessary to conduct a long-term analysis of rainfall and stream discharge data. To conduct this study, daily rainfall and stream discharge data were collected from three rain gauging and one streamflow gauging station over a period of 30 years. Data were subjected to analysis using different statistical methods such as the Modified Mann-Kendall test, Innovative Polygonal Trend Analysis (IPTA), and cross correlation analysis. The results revealed significant differences in rainfall and subsequent discharge data, with September rainfall showing a significant trend across the basin. Extreme events such as consecutive wet days and 20mm/day rainfall exhibited an increasing trend in all stations, and IPTA results indicated a significant shift in successive transition of rainfall in the South West Monsoon months. Stream flow analysis indicated an increasing trend in stream flow during September, with discharge higher than normal during this month. The cross-correlation analysis showed a delay of approximately 13, 8, and 11 days, respectively, for the rainfall to reach the stream gauge at these stations during September. These findings highlight the need to re-plan effective water resource management strategies in the Chaliyar river basin, taking into account the delay between rainfall events and the corresponding rise in stream-flow.
Abstract This study investigates groundwater quality controls and seasonal dynamics in the Mathur watershed. Analysis confirms rock-water interaction dominates water chemistry, resulting in a consistent Ca-Mg-HCO3 type. Monsoonal recharge provides regional dilution, reducing Nitrate (NO3) contamination, yet fails to alleviate pervasive quality hazards. Quality is severely constrained by high geogenic hardness (Mg exceedances) and the integration of anthropogenic inputs post-recharge (Na and NO3). Spatially, the trend analysis identifies the eastern part as the primary zone of high solute risk. Consequently, the groundwater is only moderately suitable for irrigation due to high salinity. Crucially, seasonal analysis revealed an unfavorable shift toward Very High Salinity/Medium Sodium hazard post-monsoon, indicating recharge facilitates sodium mobilization. Effective management must target the eastern zone to mitigate persistent geogenic contaminants and require strategic irrigation practices to control increasing salinity and sodium risks.
