Mapping runoff generating areas using AGNPS-VSA model

ABSTRACT

In humid regions, surface runoff is often generated by saturation-excess runoff mechanisms from relatively small variable source areas (VSAs). However, the majority of the current hydrologic models are based on infiltration-excess mechanisms. In this study, the AGricultural Non-Point Source Pollution (AGNPS) model was used to integrate the VSA concept using topographic wetness index (TWI). Both the original and AGNPS-VSA models were evaluated for a small agricultural field in Ontario, Canada. The results indicate that the AGNPS-VSA model performed better than original model. The AGNPS-VSA model predicted that only the saturated portion of the field with higher TWI values produced runoff, whereas the original AGNPS model showed uniform hydrologic response from the entire field. The results of this study are important for accurately mapping the locations of VSAs. This new model could be a powerful tool in identifying critical source areas for applying targeted best management practices to minimize pollutant loads to receiving waters.     

Boundary shock waves in a conducting gas

Summary In this paper, we have postulated, in a conducting gas, the occurrence of a boundary shock wave, considered as a quick transition region in which the viscous effects are compressive and are confined to a thin layer adjacent to a surface. The analogues of the well known Rankine-Hugoniot jump relations, Prandtl relation, and other properties of a shock wave are derived and a discussion about the existence of a boundary shock wave is made.     

Removal of Selenium by Adsorption onto Granular Activated Carbon (GAC) and Powdered Activated Carbon (PAC)

The present work involves the study of Se(IV) adsorption onto granular activated carbon (GAC) and powdered activated carbon (PAC). The adsorbents are coated with ferric chloride solution for the effective removal of selenium. The physico-chemical characterization of the adsorbents is carried out using standard methods, e. g., proximate analysis, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), thermo-gravimetric (TGA) and differential thermal analysis (DTA), etc. The FTIR spectra of the GAC and PAC indicate the presence of various types of functional groups, e. g., free and hydrogen bonded OH groups, silanol groups (Si-OH), alkenes, and CO group stretching from aldehydes and ketones on the surface of adsorbents. Batch experiments are carried out to determine the effect of various factors such as adsorbent dose (w), initial pH, contact time (t), and temperature (T) on the adsorption process. The optimum GAC and PAC dosage is found to be 10 g/L and 8 g/L, respectively, for Se(IV) removal with C₀ = 100 mg/L. The percent removal of Se(IV) increases with increasing adsorbent concentration, while removal per unit weight of adsorbent increases with decreasing adsorbent concentration. Se(IV) adsorption onto both the GAC and PAC adsorbents is high at low pH values, and decreases with increased initial pH. The results obtained are analyzed by various kinetic models. The parameters of pseudo-first order, pseudo-second order kinetics, and Weber-Morris intra particle kinetics are determined. It is seen that the sorption kinetics of Se(IV) onto GAC and PAC can be best represented by the pseudo-second order kinetic model.     

Adsorption of Selenium Using Bagasse Fly Ash

The present work involves the study of Se(IV) adsorption onto bagasse fly ash. The adsorbents were coated with a ferric chloride solution for the effective removal of selenium. The physico‐chemical characterization of the adsorbent was carried out using standard methods, e. g., proximate analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, thermo‐gravimetric analysis and differential thermal analysis. Batch experiments were carried out to determine the effect of various parameters such as adsorbent dose, initial pH, contact time, and temperature on the adsorption process. Results obtained from these studies were analyzed using various kinetic models and isotherms. Se(IV) adsorption onto adsorbent was high at low pH values, and decreased with an increase in initial pH. A temperature study showed that the uptake of Se(IV) was greatest at 293 K, within the temperature range studied. The parameters of pseudo first order, pseudo second order, and Weber‐Morris intra‐particle kinetic models were determined. Equilibrium isotherms were analyzed using Langmuir, Freundlich, and Temkin isotherms. Error analyses were also carried out using hybrid fractional error function and Marquardt's percent standard deviation.     

Assessment of CORDEX-SA experiments in representing precipitation climatology of summer monsoon over India

The present work assesses the performance of 11 regional climate simulations in representing the precipitation patterns of summer monsoon over India for the period 1970–2005. These simulations have been carried out under Coordinated Regional Climate Downscaling Experiment–South Asia (CORDEX-SA) project. The regional climate models (RCMs) have been inter-compared as well as evaluated against the observation to identify the common weaknesses and differences between them. For this, a number of statistical analysis has been carried out to compare the model precipitation field with the corresponding observation. Model uncertainty has been also evaluated through bias studies and analysis of the spread in the ensemble mean (hereafter, ensemble). The models which perform better than the rest are identified and studied to look for any improvement in the ensemble performance. These better performing experiments (best RCM experiments) are further assessed over the monsoon core region (MCR) of India. This has been done to understand how well the models perform in a spatially homogeneous zone of precipitation which is considered to be a representative region of Indian summer monsoon characteristics. Finally, an additional analysis has been done to quantify the skill of models based on two different metrics—performance and convergence including a combination of the two. The experiment with regional model RegCM4 forced with the global model GFDL-ESM2M shows the highest combined mean skill in capturing the seasonal mean precipitation. In general, a significant dry bias is found over a larger part of India in all the experiments which seems most pronounced over the central Indian region. Ensemble on an average tends to outperform many of the individual experiments with bias of smaller magnitude and an improved spatial correlation compared with the observation. Experiments which perform better over India improve the results but only slightly in terms of agreement among experiments and bias.     

On the interpretation of the distinctive pattern of geomagnetic induction observed in northwest India

The geomagnetic variation data from the 1979 Indian array experiment have been reanalyzed and reexamined using the hypothetical event analysis technique. The contour map of the |Z/H ratio replicates distinctive anomaly in northwest India previously delineated in maps of the Fourier coefficients. The anomaly reveals the presence of a significant conductor under the Ganga basin. The contour map has been used to derive a response profile perpendicular to the strike of the anomaly, for comparison with 2-D numerical models. An excellent fit was found for a conductor at a depth of 32 km, with a width of 110 km and a conductivity contrast of 1000. This result places the conductor deep within the lithosphere. In the absence of supporting data the origin of the conductor is difficult to resolve. However, it is thought to be related to pressure-released partial melting, caused by fracturing of the Indian crust during the collision of India with Asia.     

Fault type analysis along the San Andreas Fault zone: A numerical approach

Finite Element (FE) modeling under plane stress condition is used to analyze the fault type variation with depth along and around the San Andreas Fault (SAF) zone. In this simulation elastic rheology was used and was thought justifiable as the variation in depth from 0.5 km to 20 km was considered. Series of calculations were performed with the variation in domain properties. Three types of models were created based on simple geological map of California, namely, 1) single domain model considering whole California as one homogeneous domain, 2) three domains model including the North American plate, Pacific plate, and SAF zone as separate domains, and 3) Four domains model including the three above plus the Garlock Fault zone. Mohr-Coulomb failure criterion and Byerlee's law were used for the calculation of failure state. All the models were driven by displacement boundary condition imposing the fixed North American plate and Pacific plate motion along N34°W vector up to the northern terminus of SAF and N50°E vector motion for the subducting the Gorda and Juan de Fuca plates. Our simulated results revealed that as the depth increased, the fault types were generally normal, and at shallow depth greater strike slip and some thrust faults were formed. It is concluded that SAF may be terminated as normal fault at depth although the surface expression is clearly strike slip.     

Elevation,slope aspect and integrated nutrient management effects on crop productivity and soil quality in North-west Himalayas,India

On farm bio-resource recycling has been given greater emphasis with the introduction of conservation agriculture specifically withclimate change scenarios in the mid-hills of the north-west Himalaya region（NWHR）. Under this changing scenario, elevation, slope aspect and integrated nutrient management（INM） may affect significantly soil quality and crop productivity. A study was conducted during 2009-2010 to 2010-2011 at the Ashti watershed of NWHR in a rainfed condition to examine the influence of elevation, slope aspect and integrated nutrient management（INM） on soil resource and crop productivity. Two years of farm demonstration trials indicated that crop productivity and soil quality is significantly affected by elevation, slope aspect and INM. Results showed that wheat equivalent yield（WEY） of improved technology increased crop productivity by -20%-37% compared to the conventional system. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-17%. North aspect and higher elevation increased crop productivity by 15%-25% compared to south aspect and low elevation（except paddy）. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-15%. Irrespective of slope, elevation and cropping system, the WEY increased by -30% in this region due to INMtechnology. The influence of elevation, slope aspect and INM significantly affected soil resources（SQI） and soil carbon change（SCC）. SCC is significantly correlated with SQI for conventional（R2 = 0.65＊）, INM technology（R2 = 0.81＊） and for both technologies（R2 = 0.73＊）. It is recommended that at higher elevation.（except for paddy soils） with a north facing slope, INM is recommended for higher crop productivity; conservation of soil resources is recommended for the mid hills of NWHR; and single values of SCC are appropriate as a SQI for this region.