Nonlinear analysis of seasonality and stochasticity of the Indus River

Abstract

One of the world's largest irrigation networks, based on the Indus River system in Pakistan, faces serious scarcity of water in one season and disastrous floods in another. The system is dominated both by monsoon and by snow and glacier dynamics, which confer strong seasonal and inter-annual variability. In this paper two different forecasting methods are utilized to analyse the long-term seasonal behaviour of the Indus River. The study also assesses whether the strong seasonal behaviour is dominated by the presence of low-dimensional nonlinear dynamics, or whether the periodic behaviour is simply immersed in random fluctuations. Forecasts obtained by nonlinear prediction (NLP) and the seasonal autoregressive integrated moving average (SARIMA) methods show that the performance of NLP is relatively better than the SARIMA method. This, along with the low values of the correlation dimension, is indicative of low-dimensional nonlinear behaviour of the hydrological dynamics. A relatively better performance of NLP, using an inverse technique, may also be indicative of the low-dimensional behaviour. Moreover, the embedding dimension of the best NLP forecasts is in good agreement with the estimated correlation dimension. This provides evidence that the nonlinearity inherent in the monthly river flow due to the snowmelt and the monsoon variations dominate over the high-dimensional components and might be exploited for prediction and modelling of the complex hydrological system.

Citation Hassan, S. A. & Ansari, M. R. K. (2010) Nonlinear analysis of seasonality and stochasticity of the Indus River. Hydrol. Sci. J. 55(2), 250–265.     

Discretization of Complex Geometric Domain Through Computer-Based Stair-Step Representation Method for Estimating Water Levels Associated with A Storm

In this paper, an improvement has been made to the approximation technique of a complex domain through the stairstep approach to have a considerable accuracy, minimize computational cost, and avoid the hardship of manual work. A novel stair-step representation algorithm is used in this regard, where the entire procedure is carried out through our developed MATLAB routine. Arakawa C-grid is used in our approximation with (1/120)° grid resolution. As a test case, the method is applied to approximate the domain covering the area between 15°–23°N latitudes and 85°–95° E longitudes in the Bay of Bengal. Along with the approximation of the land-sea interface, coastal stations are also identified. Approximated land-sea interfaces and coastal stations are found to be in good agreement with the actual ones based on the similarity index, overlap fraction, and extra fraction criteria. The method can be used for approximating an irregular geometric domain to employ the finite difference method in solving problems related to long waves. As a test case, shallow water equations in Cartesian coordinates are solved on the domain of interest for simulating water levels due to the nonlinear tide-surge interaction associated with the storms April 1991 and AILA, 2009 along the coast of Bangladesh. The same input except for the discretized domain and bathymetry as that of Paul et al. (2016) is used in our simulation. The results are found to be in reasonable agreement with the observed data procured from Bangladesh Inland Water Transport Authority.

     

Kinematic evolution of thrusts wedge and erratic line length balancing: insights from deformed sandbox models

Kinematic evolution of fold-thrust structures has been investigated by analogue models that include syntectonic sedimentation. Different decollement dips and basement thicknesses produced different wedge geometries and propagating characteristics. A model with one decollement level was characterized by a closely spaced thrust system during early stages of shortening as compared to the late stages. The frequency of fault nucleation was rapid during the early stages of deformation. Conversely, the frequency of fault nucleation was low and thrust spacing was significantly wider in a model with two decollement levels. Individual faults became locked at steep dips and deformation stepped forward as a new fault nucleated in-sequence in front of the older locked structure. Once the thrust system was established up to 27 % overall shortening, an overlying bed was introduced to simulate syntectonic deformation. Model sand wedge did not grow self similarly but rather its length and height increased episodically with deformation. Restoration of deformed models show that layer parallel shortening accommodated for approximately half of the total model shortening across the multilayers. Calculated error in apparent layer shortening from the restored layers revealed a direct relation with depth of the layers in the models. The experimental results are comparable to a natural example from the Northern Apennines fold-and-thrust belts.     

Photo-induced degradation of emamectin benzoate: effect of iron amendments and solvent system

Photodegradation is the major dissipation pathway for emamectin benzoate (EB) in water. Therefore, the photolysis of EB was studied in distilled water (DW) and methanol under different irradiation conditions such as natural sunlight, UV tube, and artificially stimulated light (mercury lamp 125 W). The results of the study showed that EB degrades rapidly in DW than in methanol as evidenced by a photodegradation efficiency of about 75 % achieved in DW, after 24 h of irradiation with UV light, while in methanol, it was only 59.3 %. The addition of iron to EB solution in DW further enhanced its photodegradation. The rate of photodegradation of EB was recorded to be increased from 5.5 × 10^?2 to 1.0 × 10^?1 k/h after amendment with iron. The order for the rate of photodegradation of EB was DW + Fe > DW > methanol, with their respective t _1/2 values of 6.5, 12.6, and 18.7 h. Fe amendment was also found to enhance the degradation efficiency of EB even in the absence of any light (dark).     

A new model (DRASTIC-LU) for evaluating groundwater vulnerability in parts of central Ganga Plain,India

The study area is a part of central Ganga Plain which lies within the interfluve of Hindon and Yamuna rivers and covers an area of approximately 1,345 km². Hydrogeologically, Quaternary alluvium hosts the major aquifers. A fence diagram reveals the occurrence of a single aquifer to a depth of 126 m below ground level which is intercalated by sub-regional clay beds. The depth to water level ranges from 9.55 to 28.96 m below ground level. The general groundwater flow direction is northwest to southeast. Groundwater is the major source of water supply for agricultural, domestic, and industrial uses. The overuse of groundwater has resulted in the depletion of water and also quality deterioration in certain parts of the area. This has become the basis for the preparation of a groundwater vulnerability map in relation to contamination. The vulnerability of groundwater to contamination was assessed using the modified DRASTIC-LU model. The parameters like depth to water, net recharge, aquifer media, soil media, topography, impact of vadose zone, hydraulic conductivity of the aquifer, and land use pattern were considered for the preparation of a groundwater vulnerability map. The DRASTIC-LU index is computed as the sum of the products of weights and rating assigned to each of the inputs considered. The DRASTIC-LU index ranges from 158 to 190, and is classified into four categories, i.e., <160, 160–170, 170–180, and >180, corresponding to low, medium, high, and very high vulnerability zones, respectively. Using this classification, a groundwater vulnerability potential map was generated which shows that 2 % of the area falls in the low vulnerable zone, 38 % falls in the medium vulnerable zone, and 49 % of the area falls in the high vulnerable zone. About 11 % of the study area falls in the very high vulnerability zone. The groundwater vulnerability map can be used as an effective preliminary tool for the planning, policy, and operational levels of the decision-making process concerning groundwater management and protection.     

Factors affecting groundwater chemistry in regional arid basins of variable lithology: example of Wadi Umairy,Oman

Understanding factors influencing groundwater chemistry in regional groundwater basins is important to prevent groundwater pollution especially in arid areas where rainfall is low and water resources are limited. The present study assesses such factors in the regional, geologically diverse, groundwater basin of Wadi Umairy in Oman. The basin is composed of five different lithostratigraphic units with different hydraulic properties. Water samples (41) have been collected from the different units and analyzed for the major ions. Factor analysis and conventional hydrochemical methods were used to define the factors that have significant impact on the aquifer's hydrochemistry. It was found that evaporation and mineral weathering/dissolution are the main factors defining the groundwater chemistry along the flow path from recharge to discharge zones, whereas anthropogenic activities and alkalinity are found to be of lesser effect, and the latter prevails when the rocks are predominantly monomineralic. It was concluded that in regional groundwater basins, recharge/discharge relations together with the flow scale control the hydrochemistry irrespective of lithological variation in the basin.     

Long-term variability in mesopause region temperatures over Fort Collins, Colorado (41°N, 105°W) based on lidar observations from 1990 through 2007

During 1990–2007, there were 894 lidar observations of nocturnal mesopause region temperatures over Fort Collins, Colorado. In an earlier analysis with data to April 1997, an unexpected episodic warming, peaking in 1993 with a maximum value over 10 K, was reported and attributed to the Mount Pinatubo eruption in June 1991. With all data, long-term temperature trends from a 7-parameter linear regression analysis including solar cycle effect and long-term trends leads to a cooling of as much as 6.8 K/decade at 100 km, consistent with some reported observations but larger than model predictions. Including the observed episodic warming response in an 11-parameter nonlinear regression analysis reduces the maximum long-term cooling trends to 1.5 K/decade at 91 km, with magnitude and altitude dependences consistent with the prediction of two models, Spectral Mesosphere/Lower Thermosphere Model (SMLTM) and Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). In addition, the mid-latitude middle-atmospheric response to solar flux variability in Thermosphere–Ionosphere-Energetics and Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures is presented.     

Heavy metal contents in growth bands of Porites corals: record of anthropogenic and human developments from the Jordanian Gulf of Aqaba

In order to assess pollutants and impact of environmental changes in the coastal region of the Jordanian Gulf of Aqaba, concentrations of six metals were traced through variations in 5 years growth bands sections of recent Porties coral skeleton. X-radiography showed annual growth band patterns extending back to the year 1925. Baseline metal concentrations in Porites corals were established using 35 years-long metal record from late Holocene coral (deposited in pristine environment) and coral from reef that is least exposed to pollution in the marine reserve in the Gulf of Aqaba. The skeleton samples of the collected corals were acid digested and analyzed for their Cd, Cu, Fe, Mn, Pb and Zn content using Flame Atomic Absorption Spectrophotometer (FAAS). All metal profiles (except Fe and Zn) recorded the same metal signature from recent coral (1925–2005) in which low steady baseline levels were displayed in growth bands older than 1965, similar to those obtained from fossil and unpolluted corals. Most metals showed dramatic increase (ranging from 17% to 300%) in growth band sections younger than 1965 suggesting an extensive contamination of the coastal area since the mid sixties. This date represents the beginning of a period that witnessed increasing coastal activities, constructions and urbanization. This has produced a significant reduction in coral skeletal extension rates. Results from this study strongly suggest that Porites corals have a high tendency to accumulate heavy metals in their skeletons and therefore can serve as proxy tools to monitor and record environmental pollution (bioindicators) in the Gulf of Aqaba.     

Bearing capacity of sandy soil treated by Kenaf fibre geotextile

Bio-based materials are widely used recently in order to introduce a more sustainable construction material. Kenaf is a type of bio-based material that can be easily obtained in a tropical country, which could be a potential material to be utilised as a geotextile material because it has good tensile strength. The geotextile could be used to improve the bearing capacity of a loose soil. This paper presents a series of small-scale physical modelling tests to investigate the bearing capacity performance of Kenaf fibre geotextile laid on and inside the sand layer. A rigid footing was used to replicate a strip footing during the loading test, and sand was prepared based on 50% of relative density in a rigid testing chamber for ground model preparation. In order to treat the soil, Kenaf fibre geotextile was laid at four difference locations which are on the soil surface and underneath the ground model surface at 50, 75 and 100 mm deep. It was found that the usage of the Kenaf fibre geotextile has improved the bearing capacity of the sandy soil up to 414.9% as compared to untreated soil. It was also found that the depth of the Kenaf fibre geotextile treated into the soil also affects the soil performance.     

Single-station ellipticity retrieval and its joint inversion with dispersion curve,for a borehole test site

To obtain the shear wave velocity profile for engineering application to near-subsurface, many geophysical techniques are used. The dispersion curve alone is unable to provide deeper shear wave velocity information for deep soil deposit; therefore, a joint inversion of dispersion curves with the horizontal over vertical (H/V) (i.e., apparently ellipticity) curve is recommended. The H/V curve obtained from the microtremor recording contains a major part of Love wave contribution to the noise wavefield horizontal component. Due to this presence of Love wave fraction, the H/V curve does not completely replicate the ellipticity of Rayleigh wave. In this study, we try to compare the Rayleigh wave ellipticity obtained from the borehole velocity model to the H/V curve obtained at the same locality from seismic ambient noise recording. Two different techniques available for the Love effect minimization are tested and compared with the borehole ellipticity. Finally, the joint inversion of H/V and dispersion curve is made, which shows great correspondence with the previous measurement at the site.