• Volume 125, Issue 6

August 2016,   pages  1089-1311

• Modelling surface run-off and trends analysis over India

The present study is mainly concerned with detecting the trend of run-off over the mainland of India, during a time period of 35 years, from 1971–2005 May–October). Rainfall, soil texture, land cover types, slope, etc., were processed and run-off modelling was done using the Natural Resources ConservationService (NRCS) model with modifications and cell size of 5×5 km. The slope and antecedent moisture corrections were incorporated in the existing model. Trend analysis of estimated run-off was done by taking into account different analysis windows such as cell, medium and major river basins, meteorologicalsub-divisions and elevation zones across India. It was estimated that out of the average 1012.5 mm of rainfall over India (considering the study period of 35 years), 33.8% got converted to surface run-off. An exponential model was developed between the rainfall and the run-off that predicted the run-off with an $R^2$ of 0.97 and RMSE of 8.31 mm. The run-off trend analysed using the Mann–Kendall test revealed that a significant pattern exists in 22 medium, two major river basins and three meteorological subdivisions, while there was no evidence of a statistically significant trend in the elevation zones. Among the medium river basins, the highest positive rate of change in the run-off was observed in the Kameng basin (13.6 mm/yr), while the highest negative trend was observed in the Tista upstream basin (−21.4 mm/yr). Changes in run-off provide valuable information for understanding the region’s sensitivity to climatic variability.

• Groundwater sustainability assessment in coastal aquifers

The present work investigates the response of shallow, coastal unconfined aquifers to anticipated overdraft conditions and climate change effect using numerical simulation. The groundwater flow model MODFLOW and variable density groundwater model SEAWAT are used for this investigation. The transmissivity and specific yield estimated from the existing database range from 10 to 810 m^2/day and 0.08% to 10.92% respectively. After successful calibration with Nash–Sutcliffe efficiency greater than 0.80, the values of horizontal hydraulic conductivity and specific yield of the unconfined aquifer were set in the range 1.85–61.90 m/day and 0.006–0.24 respectively. After validating the model, it is applied for forecasting the aquifer’s response to anticipated future scenarios of groundwater draft, recharge rate and sea level rise. The findings of the study illustrate that saltwater intrusion is intensified in the area adjoining the tidal rivers, rather than that due to the sea alone. Of all the scenarios simulated, the immense negative impact on groundwater quality emerges due to overdraft conditions and reduced recharge with the areal extent of seawater intrusion exceeding about 67% (TDS>1 kg/m^3). The study also arrivesat the conclusion that, regional sea level rise of 1 mm/year has no impact on the groundwater dynamics of the aquifer.

• Response of a dryland fluvial system to climate–tectonic perturbations during the Late Quaternary: Evidence from Rukmawati River basin, Kachchh, western India

Dryland rivers, dominated by short-lived, localised and highly variable flow due to discrete precipitation events, have characteristic preservation potential, which serves as suitable archives towards understanding the climate–tectonic coupling. In the present study, we have investigated the fluvial records of a major, southerly-draining river – the Rukmawati River in the dryland terrain of southern Kachchh, in western India. The sediment records along the bedrock rivers of Kachchh register imprints of the Indian summer monsoon (ISM), which is the major source of moisture to the fluvial system in western India. The Rukmawati River originates from the Katrol Hill Range in the north and flows towards the south, into the Gulf of Kachchh. The field stratigraphy, sedimentology, along with the optical chronology suggeststhat a braided-meandering system existed during 37 ka period due to an overall strengthened monsoon. A gradual decline in the monsoon strength with fluctuation facilitated the development of a braided channel system between 20 and 15 ka. A renewed phase of strengthened monsoon with seasonality after around 15 ka which persisted until around 11 ka, is implicated in the development of floodplain sequences. Two zones of relatively high bedrock uplift are identified based on the geomorphometry and morphology of the fluvial landform. These zones are located in the vicinity of the North Katrol Hill Fault (NKHF) and South Katrol Hill Fault (SKHF). Geomorphic expression of high bedrock uplift is manifested by the development of beveled bedrock prior to or around 20 ka during weak monsoon. The study suggests that the terrain in the vicinity of NKHF and SKHF is uplifting at around 0.8 and >0.3 mm/a, respectively. Simultaneously, the incision in the Rukmawati River basin, post 11 ka, is ascribed to have occurred due to lowered sea level during the LGM and early Holocene period.

• Evaluation of groundwater vulnerability in El-Bahariya Oasis, Western Desert, Egypt, using modelling and GIS techniques: A case study

The Nubian Sandstone Aquifer (NSSA) is the main groundwater resource of the El-Bahariya Oasis, which is located in the middle of the Western Desert of Egypt. This aquifer is composed mainly of continental clastic sediments of sandstone with shale and clay intercalations of saturated thickness ranging between 100 and 1500 m. Vulnerability assessment to delineate areas that are more susceptible to contamination from anthropogenic sources has become an important element for sustainable resources management and land use planning. Accordingly, this research aims to estimate the vulnerability of NSSA by applying the DRASTIC model as well as utilising sensitivity analyses to evaluate the relative importance of the model parameters for aquifer vulnerability in the study area. The main objective is to demonstrate the combined use of the DRASTIC and the GIS techniques as an effective method for groundwater pollution risk assessment, and mapping the areas that are prone to deterioration of groundwater quality and quantity. Based on DRASTIC index (DI) values, a groundwater vulnerability map was produced usingthe GIS. The aquifer analysis in the study area highlighted the following key points: the northeastern and western parts of the NSSA were dominated by ‘High’ vulnerability classes while the northwestern and southeastern parts were characterised by ‘Medium’ vulnerability classes. The elevated central partof the study area displayed ‘Low’ aquifer vulnerability. The vulnerability map shows a relatively greater risk imposed on the northeastern part of the NSSA due to the larger pollution potential of intensive vegetable cultivation. Depth-to-water, topography and hydraulic conductivity parameters were found to be more effective in assessing aquifer vulnerability.

• Hydrogeochemical evolution and potability evaluation of saline contaminated coastal aquifer system of Rajnagar, Odisha, India: A geospatial perspective

The present article reports the results of a comprehensive hydrogeochemical study carried out across the coastal aquifer system of Rajnagar block, Kendrapara district, Odisha, India. The research involved collection of representative groundwater samples during the pre- and post-monsoon seasons with in situas well as laboratory measurement of various hydrogeochemical variables. Analysis of the subsurface water samples portrays an alkali dominated water type during the pre-monsoon season whereas alkaline earth has a significantly increased influence during the post-monsoon period. However, the aquifer system displays an even distribution of strong and weak acids for both the monsoonal regimes. Thehydrogeochemistry is controlled by aquifer lithology with a general occurrence of ion exchange and acid–base reaction processes across the study area. Spatial disposition of major cations indicates freshening of this coastal aquifer system in S–N and SW–NE directions. Potability analysis of the samples is suggestiveof widespread unsuitability for domestic, agriculture and industrial uses. The extensive occurrence of salinity hazards, sodium hazards and magnesium hazards across the terrain makes the groundwater unsafe for domestic and agricultural utilization while industrial potability analysis suggests the aquifer system is moderately corrosive but non-incrusting. Post-monsoon however, the subsurface waters display a general decrease in hazardous nature with increased suitability for various uses.

• study of $PM_{2.5}$ and $PM_{10}$ concentrations in the atmosphere of large cities in Gansu Province, China, in summer period

Due to rapid economic growth of the country in the last 25 years, particulate matter (PM) has become a topic of great interest in China. The rapid development of industry has led to an increase in the haze created by pollution, as well as by high levels of urbanization. In 2012, the Chinese National Ambient Air Quality Standard (NAAQS) imposed ‘more strict’ regulation on the PM concentrations, i.e., 35 and70 μg/m^3 for annual $PM_{2.5}$ and $PM_{10}$ in average, respectively (Grade-II, GB3095-2012). The Pearson’s correlation coefficient was used to determine the linear relationship of pollution between pollution levels and weather conditions as well as the temporal and spatial variability among neighbouring cities. Thegoal of this paper was to investigate hourly mass concentration of $PM_{2.5}$ and $PM_{10}$ from June 1 to August 31, 2015 collected in the 11 largest cities of Gansu Province. This study has shown that the overall average concentrations of $PM_{2.5}$ and $PM_{10}$ in the study area were 26 and $66 μg/m^3$. In PM2.5 episodedays (when concentration was more than $75 μg/m^3$ for 24 hrs), the average concentrations of $PM_{2.5}$ was 2–3 times higher as compared to non-episode days. There were no observed clear differences during theweekday/weekend PM and other air pollutants $(SO_2, NO_2, CO$ and $O_3)$ in all the investigated cities.

• Assessing the consistency between AVHRR and MODIS NDVI datasets for estimating terrestrial net primary productivity over India

This study examines the consistency between the AVHRR and MODIS normalized difference vegetation index (NDVI) datasets in estimating net primary productivity (NPP) and net ecosystem productivity (NEP) over India during 2001–2006 in a terrestrial ecosystem model. Harmonic analysis is employed to estimate seasonal components of the time series. The stationary components (representing long-termmean) of the respective NDVI time series are highly coherent and exhibit inherent natural vegetation characteristics with high values over the forest, moderate over the cropland, and small over the grassland. Both data exhibit strong semi-annual oscillations over the cropland dominated Indo-Gangetic plains while annual oscillations are strong over most parts of the country. MODIS has larger annual amplitude than that of the AVHRR. The similar variability exists on the estimates of NPP and NEP across India. In an annual scale, MODIS-based NPP budget is 1.78 PgC, which is 27% higher than the AVHRR-based estimate. It revealed that the Indian terrestrial ecosystem remained the sink of atmospheric CO$_2$during the study period with 42 TgC y$^{−1}$ NEP budget associated with MODIS-based estimate against 18 TgC y$^{−1}$ for the AVHRR-based estimate.

• Mylonitic volcanics near Puging, Upper Siang district, Arunachal Pradesh: Evidence of oblique-slip thrusting

The Abor volcanics of the continental flood basalt affinity are extensively exposed in different parts of the Siang valley. These are associated with Yinkiong Group of rocks of Paleocene–Eocene age and represent syn-sedimentary volcanism in a rift setting. Subsequent folding and thrusting of the Siyom and Rikor sequences above the Yinkiong Group of rocks represent changes from syn-to-post collisionalbrittle-ductile tectonic episodes. Mylonitic Abor volcanics in the thrust contacts are studied at several locations in the north and south of Puging in the Siang valley. Both the Abor volcanics and associated Rikor and Yinkiong Group of rocks preserve meso to micro-scale fabric asymmetries indicating that the thrust contacts are shear zones of brittle-ductile nature containing mylonitic textures of high shear strain.Two distinct hitherto unrecognised shear zones in the north and south of Puging are named as North Puging Shear Zone (NPSZ) and South Puging Shear Zone (SPSZ). The kinematic indicators along the thrust contact indicate oblique slip thrusting of the Rikor and Siyom thrust sheets above the Yinkiong Group of rocks. This paper provides field evidence proving that the compression due the Burmese plate made oblique slip thrusting and zones of mylonitised volcanics possible and associated metasediments were formed. The kinematic indicators in the NPSZ and SPSZ respectively indicate top-to-SSE and top-to-NNW sense of shears.

• Role of smectite-rich shales in frequent foundation failures in southeast Nigeria

This paper investigated the geotechnical properties of smectite-rich shale, and its implications as foundationmaterial. Ten expansive shale samples were collected from foundation materials at Akpugo in Nkanu West L.G.A. of Enugu State, southeast Nigeria. Samples were subjected to grading, Atterberg limitscum-compaction tests, slake durability, specific gravity, permeability, undrained triaxial tests and x-raydiffraction scan. Fines and sand contents of the soil samples range from 51–97% and 3–49% respectively. Liquid limit, plastic limit and plasticity index have average values of 60.7, 19.1 and 43.3% respectively. Linear shrinkage and free swell showed average of 16.3% and 76%. These results are indicative of predominantclay soil with high plasticity, compressibility and water holding capacity. XRD scan established presence of smectite and illite clay minerals, confirming soil high plasticity, capable of causing instability in foundation soil. The shale achieved maximum dry density range between 1.79 and 1.94 kg/m$^3$ atoptimum moisture content range of 6.9–12.8%, indicating poor to fair foundation materials. The shale cohesion ranges from 15 to 30 kPa while the angle of friction ranges between 10◦ and 18◦, signifying an average strength soil material. Samples slake durability index and specific gravity fall within 24–55%and 2.50–2.58 respectively, suggesting non-durable and weak soil. Permeability of the samples ranges between 7.36×10$^{−6}$ and 4.77×10$^{−8}$ cm/s which suggested low drainage capable of causing water-log at sites. Therefore, the shale could be generally classified as poor to fair foundation material, which on moistureinflux experience reduction in strength due to deterioration of its constituent minerals, especiallyclay and cement materials during the lifespan of engineering structures. Authors therefore recommendmodification of foundation soil, appropriate foundation design and good drainage control as ways ofimproving stability of engineering structures underlain by expansive shale.

• Ionospheric response to X-class solar flares in the ascending half of the subdued solar cycle 24

The signature of 11 X-class solar flares that occurred during the ascending half of the present subdued solar cycle 24 from 2009 to 2013 on the ionosphere over the low- and mid-latitude station, Dibrugarh (27.5◦N, 95◦E; magnetic latitude 17.6◦N), are examined. Total electron content (TEC) data derived from Global Positioning System satellite transmissions are used to study the effect of the flares on the ionosphere. A nonlinear significant correlation ($R^2$ =0.86) has been observed between EUV enhancement (ΔEUV) and corresponding enhancement in TEC (ΔTEC). This nonlinearity is triggered by a rapid increase in ΔTEC beyond the threshold value ∼1.5 (×1010 ph cm$^{−2} s^{−1})$ in ΔEUV. It is also foundthat this nonlinear relationship between TEC and EUV flux is driven by a similar nonlinear relationship between flare induced enhancement in X-ray and EUV fluxes. The local time of occurrence of the flares determines the magnitude of enhancement in TEC for flares originating from nearly similar longitudeson the solar disc, and hence proximity to the central meridian alone may not play the dominating role. Further, the X-ray peak flux, when corrected for the earth zenith angle effect, did not improve thecorrelation between ΔX-ray and ΔTEC.

• Satellite evidence for no change in terrestrial latent heat flux in the Three-River Headwaters region of China over the past three decades

Terrestrial latent heat flux (LE) in the Three-River Headwaters region (TRHR) of China plays an essential role in quantifying the amount of water evaporation and carbon sink over the high altitude Tibetan Plateau (TP). Global warming is expected to accelerate terrestrial hydrological cycle and to increase evaporation. However, direct field observations are lacking in this region and the long-term variability in LE remains uncertain. In this study, we have revised a semi-empirical Penman LE algorithm based on ground eddy covariance (EC) observations from an alpine grass site and provided new satellite-based evidence to assess LE change in the TRHR during 1982–2010. Our results show that the average annual terrestrial LE in the TRHR is about 38.8 W/m$^2$ and there is no statistically significant changein annual LE from 1982 to 2010. We also found that during the same time period, terrestrial LE over the east region of the TRHR significantly decreased, on average, by 0.7 W/m$^2$ per decade, which was driven primarily by the surface incident solar radiation (Rs) limitation, offsetting the increased LE over the west region of the TRHR caused by the increased precipitation (P) and soil moisture (SM).

• Hydroclimatic dynamics in southwestern Romania drylands over the past 50 years

The present paper examines hydroclimatic dynamics in southwestern Romania drylands, which is one of the country’s most heavily affected regions by climate change. The analysis focuses on two of the region’s representative catchments (Drincea and Desnatui), covers the past five decades (1961–2009), and is basedon climate data (mean monthly and annual climatic water balance values – CWB, expressed in mm) and hydrological data (mean monthly and annual streamflow rate values – SFR, expressed in m$^3$/s). The data were provided by five regional weather stations, i.e., by five gauging stations located within the two catchments. The analysis was conducted on three temporal scales (annual, seasonal and monthly), and used statistical methods, such as Mann–Kendall test/Sen’s slope method for trend analysis, and Spearman/Student test for the statistical association between climatic and hydrological parameters. The results indicated an overall increase in climatic water deficit, with direct effects on streamflow reduction.Statistically significant trends (climatic water deficit increase and streamflow decrease) were identified especially in spring (with maximum rate values of (−1.66 mm/yr)/(−81.3 mm/49 yrs), for the CWB, and (−0.02 m$^3$/s/yr)/(−0.9 m$^3$/s/49 yrs), for the SFR). In some cases (mainly in the autumn months) it was found that, while climatic water deficit has decreased, the streamflow rate has increased. Statistical correlations revealed the relationship between the considered hydroclimatic parameters, with a particularly high statistical significance in spring and summer. Weak and inverse correlations between climatic and hydrological parameters can be explained by the role of other factors controlling the streamflow,both natural (soil and lithology) and anthropogenic (wetland drainage, water body conversion, dam and reservoirs building).

• Emission quantification of refrigerant CFCs, HCFCs and HFCs in megacity Lahore (Pakistan) and contributed ODPs and GWPs

An integrated assessment of emissions of some important refrigerant ozone depleting substances (ODSs) (CFC-11, CFC-12, HCFC-141b and HFC-134a) and their contributed ozone depletion potentials (ODPs) and global warming potentials (GWPs) have been made in the megacity Lahore (Pakistan) for the periodfrom 2005 to 2013. During the production of 6.488 million refrigerator units, the cumulative estimated emissions of CFC-11, CFC-12, HCFC-141b and HFC-134a were 129.7, 6.8, 1257 and 104 mega grams (1 Mg = 106 grams). The estimated GWP (CO2-eq) and ODP (CFC 11-eq) associated with productionphase emissions of these four gases were 616.07, 73.52, 910.96, and 87.36 kilotonnes, and 129.7, 6.8, 139.4, and 0 tonnes, respectively. ODP of HFC-134a is considered to be zero. In addition, the repair and maintenance of 81.2 thousand units resulted in 10.8 Mg emissions of CFC-12 with 10.8 tonnes ODP(CFC11-eq) and 117,802 tonnes GWP (CO2-eq) that were higher than the HFC-134a emissions recorded at 4.3 Mg causing 4563 tonnes GWP(CO2-eq). A decrease in ODP (CFC 11-eq) and GWP (CO2-eq) at the rate of −8.3% and −8.2% per year is observed to be contributed by all the selected ODSs during the study period.

• Evidence for a fluid flow triggered spatio-temporal migration of seismicity in the 2001 M$^w$ 7.7 Bhuj earthquake region, Gujarat, India, during 2001–2013

We studied the variations in spatial and temporal clustering of earthquake activity (during 2001–2013) in the Kachchh seismic zone, Gujarat, India, by precisely relocating 3478 events using a joint hypocentral determination (JHD) relocation technique, and high-quality arrival times of 21032 P- and 20870 S-waves.Temporal disposition of estimated station corrections of P- and S-waves suggests that the fluid flow in the causative fault zone of the 2001 Bhuj mainshock increased during 2001–2010, while it reduced during 2011–2013, due to the healing process associated with the perturbed Kachchh fault zone. We also estimated the isotropic seismic diffusivities from epicentral growth patterns, which are found to bemuch lower than those observed for reservoir-induced seismicity sites in the world. Finally, we analysed the spatial and temporal evolution of this earthquake sequence by solving the diffusion equation of pore-pressure relaxation caused by co- and post-seismic stress changes associated with earthquakes. The value of the isotropic diffusivity is estimated to be 100 m2/s for the Kachchh rift zone. This gives a higher permeability (after a lapse time of 14 years from the occurrence of the 2001 Bhuj mainshock) in comparison to those observed for other intraplate regions in the world. Our results suggest that the observed spatio-temporal migration of seismicity is consistent with the shallow (meteoric water circulationat 0–10 km depths) and deeper (metamorphic fluid and volatile CO2 circulation at 10–40 km depths) fluid flows in the permeable and fractured causative fault zone of the 2001 Bhuj earthquake.

• Rainfall–runoff temporal variability in Kermanshah province, Iran and distinguishing anthropogenic effects from climatic effects

Investigation of changes in rainfall and runoff patterns in various regions and determining their relationship in the sense of hydrology and climatology are of great importance, considering those patterns efficiently reveal the human and natural factors in this variability. One of the mathematical methods to recognise and model these fluctuations is Wavelet Analysis. This is a spectral method used in multivariateanalysis and also tracing fluctuations in temporal series. In this study, continuous wavelet transformation is used to identify temporal changes in rainfall–runoff patterns. The hydrological and rain gauge data were collected from in situ measurements of Kermanshah province located in the western border of Iran.Precipitation anomalies were reconsidered in a number of stations, including Kermanshah, for a period of 55 years (1955–2010) and discharge of Gamasiab River in Polchehr station, discharge of Khoram Rood River in Aran-Gharb station and discharge of Gharasoo River in Polekohne station. In addition, anomaliesof the climatic teleconnections were studied to emphasise the climatological effects on the runoff pattern in the region. The role of natural and anthropogenic effects (land use changes) has been distinguished and identified, using the comparison of the teleconnections and hydrological data. The results achieved from three stations show that there was an approximate correlation between rainfall, runoff and teleconnections until the year 1995; however, after 1995, a great difference appeared among them, specifically for the Aran-Gharb station (Khoram Rood River). The post-1995 slope of cumulative standardised anomaly is much steeper in the case of runoff compared to rainfall. As there were no significant climate changes in the region, it could be concluded that the runoff decrease is not caused by climatechanges, but by anthropogenic effects, human interventions and extra water usage from the surface and underground water resources for agriculture and economic purposes.

• # Journal of Earth System Science

Current Issue
Volume 128 | Issue 8
December 2019

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019