RESUMEN

Significant changes in rainfall patterns are critical to agriculture, and the dependency of cropping systems on rainfall variability would engender appropriate farming practices and agriculture policies for a climate-resilient agriculture system. This study analyses the significance of rainfall variability on agriculture productivity in the Wayanad district of Kerala (India) using time series data on rainfall (1989-2019) and crop yield (2000-2019). The spatial variability of rainfall patterns reveals a dichotomy between the rain gauge stations in the northern and southern parts of the region. Despite the absence of statistically significant trends in the monthly, seasonal and annual rainfall, based on the Mann-Kendall trend analysis, an increase in the yield of many crops (e.g., winter paddy, banana) is evident, which emphasises the critical role of irrigation in driving the crop productivity. As an adaptation strategy to changing rainfall patterns, irrigation would meet the additional crop water requirement for sustainable agricultural production under the varying rainfall distributions. However, the increase in the area under irrigation in recent years has had significant implications for both surface water and groundwater resources. The conclusive findings suggest that the region requires climate-resilient agriculture, focusing on optimising irrigation and developing sustainable agriculture and water conservation strategies.

Asunto(s)

RESUMEN

The quantitative and qualitative stress on groundwater resources has been witnessed across the globe. The current study assesses the groundwater quality of Tirunelveli district which faces the hazard of groundwater contamination through seepage of toxins, considering the open dumping of huge volumes of solid waste. The findings from this study confirmed the presence of more than 20% samples in the "poor to very poor" quality with high concentrations of TDS, Cl-, and NO3-, unfit for drinking, and other domestic purposes. The spatial distribution of TDS and NO3- highlighted the potential impact of solid waste dumping in the nearby landfill sites. K-means hierarchical clustering and multivariate analysis suggested that salinization and nitrate pollution was highly influenced by anthropogenic sources in comparison to geogenic sources. Rock water interaction and evaporation processes emerged as the two major dominant natural mechanisms controlling the groundwater chemistry. Four hydro-chemical facies were identified in the order of Ca-HCO3 > Ca-Mg-Cl > Na-Cl > mixed Ca-Na-HCO3. Thus, this study creates an urgent need of mitigation measures towards curbing and management of solid waste disposal and hence, the potential hazard of contaminant seepage into the groundwater.

RESUMEN

Coastal lakes and estuaries are considered economic drivers for coastal communities by delivering invaluable economic and ecosystem services. The coastal ecosystems are facing recurrent hypoxia events (dissolved oxygen; DO < 2.0 mg L-1) and are emerging as a major threat to ecosystem structure and functioning. The Ashtamudi Lake, (area = 56 km2), is one of the Ramsar sites in the State of Kerala and located on the SW coast of India. The waterways are extensively used for backwater tourism and for fishery activities. This paper discusses the spatio-temporal variation of water quality attributes with emphasis on hypoxia during non-monsoon and monsoon seasons. The extent of hypoxia on fishery diversity was discussed. The Southern Zone, adjacent to the urban area, shows the hypoxic condition with higher concentration of BOD, NO3-N, and NH4-N. The hypoxic condition is largely limited to the Southern Zone in both seasons. The occurrence of low DO in the lake is highly related to salinity and organic load in the lake system. The tracking of pollution sources in the lake system was also done through identification of pollution potential zones and found that catchments adjacent to Southern and Western Zones (urban regions) are the major source of pollution. The study suggests that hypoxia is chiefly attributed to anthropogenic interventions in the form of discharge of wastes into the lake causing overloading of nutrients and organic effluents, decrease in the freshwater supply, the absence of proper freshwater mixing or dilution, and effluent discharge from nearby urban centers.

Asunto(s)

RESUMEN

Radon (222Rn) is a colourless, odourless, inert, and radioactive noble gas (t1/2 = 3.8 days) that emanates from rocks and soils as a result of the alpha decay of its parent, radium (226Ra) in the decay series of uranium-238, is the focus of this study. Radon is produced in the crystal lattice of the minerals and emanates out through alpha recoil. It dissolves in water, and is also found in soil and air. Its distribution in water is more pertinent for scientific investigations. It can be measured by various methods. Certain properties of radon enable it to serve as an ideal tracer, viz., short-half life, inertness, high abundance in groundwater than surface water, preferential partitioning, sensitivity to sudden changes in subsurface conditions, non-invasiveness etc. This paper reviews the state-of-the-art techniques on the measurement of dissolved radon in water and its potential applications as a tracer and precursor in several hydrogeological and geological applications like understanding the surface water - groundwater interactions, hydrograph separation of streams, estimation of Submarine Groundwater Discharge (SGD), study of hydrodynamics and water balance of lakes, earthquake predictions, locating geological structures (faults/lineaments), geochemical explorations, NAPL contamination studies etc. Among the various applications presented, radon based approach is found to be more reliable in water resources domain than seismic precursory studies. The interpretations based on radon study in the above applications will pave the way for the improved understanding of the hydrological processes, and thus, help the planners and water managers for the sustainable development and management of water resources.

Asunto(s)

RESUMEN

Nutrient pollution of rivers is one of the prime threats facing the aquatic systems. In the present study, water samples (n = 20) were collected from the Karamana river (KR) during the pre-monsoon (PMN) and monsoon (MN) seasons of 2019 to analyze the seasonal variations. The water samples were analyzed for various physico-chemical parameters and to understand the nutrient status of the river. Furthermore, gross primary productivity (GPP), net primary productivity (NPP) and phytoplankton analysis were carried out to assess relationship among productivity variables and phytoplanktons. The study revealed that water quality is better during MN than PMN due to dilution. Among the two seasons, PMN showed relatively higher values for most of parameters like pH, EC, TDS, TA, Cl, NH4-N, NO3-N, NO2-N, Chl-a, GPP and NPP. The correlation among GPP, NPP, nutrients and other water quality parameters were done using SPSS. Phytoplankton of 23 genera belonging to three classes, namely Chlorophyceae (40%), Bacillariophyceae (40%) and Cyanophyceae (20%) have been identified in KR. The various phytoplankton diversity indices and statistical analyses were estimated and their relevance discussed in this paper. The nutrient enrichment in the downstream regions was affected the phytoplanktonic structure and diversity of the river.

Asunto(s)

RESUMEN

The management of wastewater generated as a byproduct of various human activities from agricultural, industrial, and domestic sectors is a matter of global concern today. Greywater is a class of wastewater generated from the domestic sector. Greywater management can be done effectively by treating greywater at the source itself. In this context, constructed wetlands (CWs) come handy with low-tech, environmental, and economic-friendly options. In the present study, box-type horizontal subsurface flow constructed wetlands were designed and the efficiency of Napier grass (Pennisetum purpureum), Vetiver (Vetiveria zizanioides), and Equisetum (Equisetum hyemale) were assessed in treating domestic greywater. There was a drastic significant increase in DO with 47.0% in Vetiver, 92.5% in Napier grass, and 97.2% in Equisetum. The average percent pollutant removal of some major parameters was 92.4% for turbidity, 92.7% for acidity, 81.3% for BOD, 91.0% for COD with Napier grass. In the case of Vetiver, the removal percent was 82.5% turbidity, 87.9% acidity, 81.8% BOD, and 92.9% COD. For Equisetum, the average pollutant removal efficiency varied with 94.6% turbidity, 91.4% acidity, 80.0% BOD, and 88.1%COD. The study thus proves the efficiency of all the three plants to be used in box-type constructed wetlands.

Asunto(s)

RESUMEN

A comprehensive study was conducted to understand the radon (222Rn) distribution and associated radiation doses to the public in a small tropical river basin partly set in the western slope of the Southern Western Ghats of Kerala, India. Radon, though detected in all the 71 monitored wells (0.17-68.3 Bq L-1), exceeded the maximum contamination level (MCL) of 11.1 Bq L-1 for drinking water recommended by United States Environmental Protection Agency (USEPA) in eight samples from isolated pockets of highland, midland and lowland of the Karamana River Basin (KRB) and found to be well within 100 Bq L-1, the parametric value suggested by the World Health Organization (WHO) and the European Union (EU). The age-wise total annual effective doses (AEDs) of groundwater radon activity ranged from 0.5-208.4 µSv a-1 for infants, 0.4-172.2 for children and 0.5-189.7 µSv a-1 for adults. The results reveal that effective doses due to groundwater radon pose no potential public health risk in the study region. Since there is no previous background information on radon-induced radiation dose in the KRB, this work is a newfangled attempt from a public health point of view.

Asunto(s)

RESUMEN

Studies on occurrence of radon in the environment are receiving growing attention worldwide due to its adverse impact on human health. Despite that, the dissolved radon in water is found to be a useful tracer in many hydrogeological studies. Although, several studies focused on the occurrence of high 222Rn in groundwater, the processes responsible for its variation is still not well understood. Hence, an attempt has been made in the present study to elucidate the underlying factors influencing the abundance 222Rn in hard rock (gneissic) aquifers of Karamana River Basin, southwest India. 222Rn in groundwater was analyzed in 71 dug wells during the pre-monsoon period of 2017. A large variability in 222Rn activities (170-68,350 Bq/m3) was noticed in groundwater and high activities were mainly seen in the khondalite formation. No significant dependencies between 222Rn activity and depth to water table, groundwater temperature and electrical conductivity were observed. However, majority of the presence of high 222Rn activity in groundwater matches with the location of lineaments. Furthermore, radium content in the host rock, degree of weathering and fracturing and the emanation coefficient of the rock were found to have an important bearing on the occurrence of radon in groundwater. The underlying factors influencing the abundance of radon in hard rock aquifers were also conceptualized. Thus, the study highlights the usefulness of 222Rn as a potential tool in delineating the macro-structural features like fractures/lineaments that are significant repositories of groundwater, which could be explored for groundwater development in hard rock terrains.

Asunto(s)

RESUMEN

A total of 42 (21 surface water and 21 bed sediments) samples were collected from upstream to downstream stretches of Meenachil river during pre-monsoon (PRM), monsoon (MON) and post monsoon (POM) seasons. DOC in water showed increasing trend spatially while temporal study illustrates high mean value during PRM (1.58 ppm) followed by POM (0.97) and MON (0.36). Spatial assessment of elements such as Ca, Mg, K and Na in sediments reveals erratic trend during different seasons, while total phosphorous showed escalating trend signifying abrupt addition from anthropogenic sources. Based on characteristic carbon to nitrogen ratio, the study demonstrates significant control of macrophyte in terrestrial organic matter accumulation along downstream stations.

Asunto(s)

RESUMEN

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.

Asunto(s)

RESUMEN

Discriminant analysis (DA) was performed on river hydrochemistry data for three seasons (i.e., monsoon (MON), post-monsoon (POM), and pre-monsoon (PRM)) to examine the spatio-temporal hydrochemical variability of two mountain river basins (Muthirapuzha River Basin (MRB) and Pambar River Basin (PRB)) of the southern Western Ghats, India. Although the river basins drain tropical mountainous terrain, climate and degree of anthropogenic disturbances show significant differences (i.e., humid, more disturbed MRB vs semiarid, less disturbed PRB). In MRB, TDS, Na(+), pH, Mg(2+), and K(+) are the attributes responsible for significant hydrochemical variations between the seasons, while Cl(-), TH, and Na(+) are the predictors in PRB. The temporal discriminant models imply the importance of rainfall pattern, relative contribution of groundwater toward stream discharge and farming activities in hydrochemistry between the seasons. Inclusion of hydrochemical attributes (in the temporal discriminant functions) that can be derived from both natural and anthropogenic sources suggests that ionic enrichment strongly depends on the seasons, and is mainly due to the variability in the intensity of anthropogenic activities as well as fluctuations in river discharge. In spatial discriminant models, Cl(-) is the only variable responsible for hydrochemical variations between the basins (during MON), whereas Si discriminates during POM and PRM, implying the role of atmospheric supply, anthropogenic modifications as well as intensity of weathering. In the spatial discrimination models, misclassification of hydrochemistry data between MRB and PRB can be attributed to the overlapping effect of humid climate of MRB extending toward the upstream of (semiarid) PRB. This study underscores the versatility of DA in deciphering the significance of climatic controls on hydrochemical composition of tropical mountain rivers.

Asunto(s)

RESUMEN

Texture plays an important role in the identification of polluted stretch in a lake system. The organic matter as well as toxic elements get accumulated in the finer sediments. The aim of the work is to show the spatio-temporal distribution of texture of the lake sediment (Akkulam-Veli lake, Kerala) and to identify the hot spot areas of contamination. Hot spot areas vary with seasons. During PRM, (premonsoon), the upstream portion of the Akkulam lake is the hot spot. During MON (monsoon), the downstream portion of the Akkulam lake and the upstream portion of the Veli lake are the hot spots. During POM (postmonsoon), hot spot area is the downstream portion of the Akkulam lake. This methodology can be used for the quick identification of hot spots in water bodies.

Asunto(s)

RESUMEN

Heavy metals are widespiead pollutants of great environmental concern as they are non degradable, toxic and persistent.with serious ecological ramifications on aquatic ecology. The objective of this study is to analyse the spatio-temporal variation of heavy metals in the sediments of a lake system (Akkulam-Veli lake, Kerala). Correlation analysis .has been conducted to determine the factors that influence the accumulation of heavy metals. High cadmium content is observed during premonsoon (PRM) due to the reduction in salinity in the lake water and is absent during postmonsoon (POM) due to increase in salinity and. dissolved oxygen. A hike in lead content can be observed during monsoon (MON). Heavy metal concentration is high during monsoon due to urban runoff. Heavy metals are accumulated in clay during PRM. During MON and POM, heavy metals found accumulated in silt fraction of sediment.

Asunto(s)

RESUMEN

Lakes are seriously affected due to urban pollution. The study of the morphological features of a lake system helps to identify its environmental status. The objective of the present study is to analyse the influence of morphometry on water quality in a lake (Akkulam-Veli Lake, Thiruvananthapuram, Kerala). The morphological features namely mean depth, surface area, volume, shoreline length, shoreline development and index of basin permanence have been evaluated. Correlation analysis has been conducted to determine the relationship between morphological features and water quality. Regression analysis has been conducted to find out the extent of influence of morphometric features on water quality. The study revealed that the lake is less affected by wind-induced wave action due to various reasons. The depth and volume have significant role in the water quality. The nitrogen fixation of blue green algae can be observed from the morphological features. The morphology has greater role in the water quality of a lake system.

Asunto(s)

RESUMEN

Water pollution has now become a major threat to the existence of living beings and water quality monitoring is an effective step towards the restoration of water quality. Lakes are versatile ecosystems and their eutrophication is a serious problem. Carlson Trophic State Index (CTSI) provides an insight into the trophic condition of a lake. CTSI has been modified for the study area and is used in this study. Satellite imagery analysis now plays a prominent role in the quick assessment of water quality in a vast area. This study is an attempt to assess the trophic state index based on secchi disk depth and chlorophyll a of a lake system (Akkulam-Veli lake, Kerala, India) using Indian Remote Sensing (IRS) P6 LISS III imagery. Field data were collected on the date of the overpass of the satellite. Multiple regression equation is found to yield superior results than the simple regression equations using spectral ratios and radiance from the individual bands, for the prediction of trophic state index from satellite imagery. The trophic state index based on secchi disk depth, derived from the satellite imagery, provides an accurate prediction of the trophic status of the lake. IRS P6-LISS III imagery can be effectively used for the assessment of the trophic condition of a lake system.

Asunto(s)

RESUMEN

Eutrophication has become a serious threat to the lake systems all over the world. This is mainly due to the pollution caused by anthropogenic activities. Carlson trophic state index (CTSI) is commonly used for the classification of trophic conditions of surface waters. The study is conducted to assess the trophic status of a tropical lake (Akkulam-Veli lake, Kerala, India) using CTSI based on Secchi disc depth (SD), total phosphorus (TP) and chlorophyll-a. The TSI values based on SD and TP are high (>70), indicating the hypereutrophic state which needs urgent action for the restoration of the fragile ecosystem. The higher TP in both lakes, and the lower value of chlorophyll-a in the Akkulam part, warrant explanation, are discussed here. The influence of other biochemical parameters in both the Akkulam and the Veli part of the lake has been assessed. Correlation analysis is conducted to study the effect of various water quality parameters. The variation in the water quality before and after the opening of sand bar is studied using paired t test. As almost all the lakes in the world are experiencing similar situation of extinction, this study is helpful to have an insight in the hydrochemistry of the lake as well as to identify the worst affected areas of the lakes.

Asunto(s)

RESUMEN

Levels of heavy metals (Cu, Cr, Pb, Zn, Fe and Mn) in the surficial sediments of the four coastal wetlands, viz. Poovar, Poonthura, Akkulam-Veli and Kadinamkulam-Anjengo-Akathumuri of Thiruvananthapuram are presented in this study. Further the statistical tools like contamination factor (CF), index of geoaccumulation (Igeo) and pollution load index (PLI) are used to assess the heavy metal pollution. Among the wetlands, Poonthura and Akkulam-Veli were polluted by the heavy metals, as very high values are observed for Pb and Cu indicating high build up of these metals in the sediments. The highest value of CF can be attributed to anthropogenic inputs mainly from urban domestic sewage and land run-off. Based on the value of CF, PLI and Igeo, the Poonthura and Akkulam-Veli wetlands are identified as potential 'hot spots' in the district.

Asunto(s)