Hydrochemical investigation of open well and river water samples of Thuthapuzha Sub-basin of Bharathapuzha, Kerala, was carried out to determine the spatial and temporal variations in the physico-chemical parameters. The suitability of water for drinking and irrigation purposes and the processes controlling the water chemistry were also assessed. The study area experiences a humid tropical climate and heavy rainfall of ~ 3830 mm/year. Thirty-five open well and nine river water samples were collected during the pre-monsoon, monsoon and post-monsoon seasons. The chemical properties of the river water samples were dominated by alkaline earths and weak acids (CaHCO 3 type). Even though majority of the open well samples belonged to CaHCO 3 type, few samples belonged to NaCl, mixed CaMgCl and mixed CaNaHCO 3 water type. The groundwater and river water chemistry of the region was influenced by the chemistry of the host rock rather than precipitation and evaporation. Except pH and the total iron concentration, all other physico-chemical parameters of the open well samples of the study area were within the acceptable limit of drinking purposes. The physico-chemical parameters of the entire river water samples were within the acceptable limit for drinking purpose. The entire open well and river water samples were suitable for irrigation purposes.
Isotopic composition of monthly composite precipitation samples from Kozhikode (n = 31), a wet tropic station and Hyderabad (n = 25), a semi-arid station across southern India were studied for a period of four years from 2005 to 2008. During the study period, the Kozhikode station recorded an average rainfall of 3500 mm while the Hyderabad station showed an average rainfall of 790 mm. The average stable isotope values in precipitation at the Kozhikode station were δ 18 O = −3.52‰, d-excess = 13.72‰; δ 18 O = −2.94‰, d-excess = 10.57‰; and δ 18 O = −7.53‰, d-excess = 13.79‰, respectively during the pre-monsoon (March-May), monsoon (June-September) and post-monsoon (October-February) seasons. For the Hyderabad station, the average stable isotope values were δ 18 O = −5.88‰, d-excess = 2.34‰; δ 18 O = −4.39‰, d-excess = 9.21‰; and δ 18 O = −8.69‰, d-excess = 14.29‰, respectively for the three seasons. The precipitation at the two stations showed distinctive isotopic signatures. The stable isotopic composition of precipitation at the Hyderabad station showed significant variations from the global trend while the Kozhikode station almost followed the global value. These differences are mainly attributed to the latitudinal differences of the two stations coupled with the differences in climatic conditions.
The stable isotopic compositions of all major daily rain fall samples (n = 113) collected from Kozhikode station in Kerala, India, for the year 2010 representing the pre-monsoon, southwest and northeast monsoon seasons are examined. The isotopic variations δ(18)O, δ(2)H and d-excess in daily rainfall ranged from δ(18)O: -4.4 to 2 ‰, δ(2)H: -25.3 to 13.8 ‰, and d-excess: -2.4 to 15.3 ‰; δ(18)O: -9.7 to -0.6 ‰, δ(2)H: -61.7 to 5.3 ‰, and d-excess 5.8 to 17.4 ‰; δ(18)O -11.3 to -1.4 ‰, δ(2)H: -75.3 to 0.9 ‰, and d-excess: 8.8 to 21.3 ‰ during the pre-, southwest and northeast monsoon periods, respectively. Thus, daily rainfall events during two monsoon periods had a distinct range of isotopic variations. The daily rain events within the two monsoon seasons also exhibited periodic variations. The isotopic composition of rain events during pre-monsoon and a few low-intensity events during the southwest monsoon period had imprints of secondary evaporation. This study analysing the stable isotopic characteristics of individual rain events in southern India, which is influenced by dual monsoon rainfall, will aid in a better understanding of its mechanism.
Environmental carrying capacity is a measure of competence of a lake to accommodate pollution inputs without degrading water quality. In the research reported here, we identified the factors influencing the environmental carrying capacity of Vellayani Lake or VL (a typical tropical freshwater lake), Thiruvananthapuram, Kerala State, India. R-mode factor analysis is used to identify the factors controlling the carrying capacity of the lake, whereas hierarchical cluster analysis (HCA) helped to classify the lake. The carrying capacity of the lake is low with respect to alkalinity, due to ion deficiency, and is potentially reactive to sudden changes in pH. Eutrophic condition exists in the entire lake system. Acidic factor, mineralization factor, fertilizer factor (P & K), evaporation factor and organic pollution factor are the controllers of VL water quality during the pre-monsoon period. The same factors (but not evaporation factor) and an additional runoff factor control the water quality during monsoon. In the post-monsoon, the aforesaid factors (other than runoff, alkalinity) and soil erosion factor influence the water quality. Hence, managers of the lake system need to also focus on combating acidic factor during pre- and post-monsoons and runoff during monsoon. Smaller areal extent and shallow depth of VL, reduced outflow from it, less rainfall, presence of lateritic rock and soil and absence of limestone strata in the catchment are the chief elements affecting the acidic factor of Vellayani Lake.
The stable isotope analysis of all major rain events from Moinabad (MB), Rajendranagar (RN) and Osmanasagar (OS) reservoir, three closely placed locations in Hyderabad, India, were carried out during the 2005 to 2008 period. The OS station recorded the highest amount of rainfall with an average value of 1000 mm, whereas the MB station recorded the lowest average rainfall of 790 mm. The stable isotope (d 18 O) values of the precipitation samples during these period varied from À11.43% to À0.03% for the MB station, À8.21% to 0.54% for the RN station and À11.47% to 0.72% for the OS station. The d-excess of precipitation at the three stations also showed considerable variations and revealed that the precipitation in the region undergoes significant modification through secondary evaporation during its fall. The possible causes for these observed spatial and temporal variations in amount and the isotopic composition of precipitation in a small geographical area within the city were studied. The observed variations may be attributed to the regional scale differences in water budget induced by rapid urbanisation activities in the city coupled with the differences in secondary effects undergone by the falling drops. This study elucidating changes in precipitation patterns in the city and its possible causes may largely help in its water balance calculation.
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