The Himalayan cryosphere: A critical assessment and evaluation of glacial melt fraction in the Bhagirathi basin

The cryosphere constitutes an important subset of the hydrosphere.The Himalayan cryosphere is a significant contributor to the hydrological budget of a large river system such as the Ganges.Basic data on the cryosphere in the Himalaya is inadequate and also has large uncertainties.The data on glacial melt component in the Himalayan rivers of India also shows high variability.The Gangotri glacier which constitutes nearly a fifth of the glacierized area of the Bhagirathi basin represents one of the fastest receding,large valley glaciers in the region which has been surveyed and monitored for over sixty years.The availability of measurement over a long period and relatively small glacier-fed basin for the Bhagirathi river provides suitable constraints for the measurement of the glacial melt fraction in a Himalayan river.Pre- and post-monsoon samples reveal a decreasing trend Of depletion of δ~(18)O in the river water from glacier snout(Gaumukh) to the confluence of the Bhagirathi river with the Alaknanda river near Devprayag.Calculations of existing glacial melt fraction(~ 30%at Rishikesh) are not consistent with the reported glacial thinning rates.It is contended that the choice of unsuitable end-members in the three component mixing model causes the overestimation of glacial melt component in the river discharge.Careful selection of end members provides results(~11%at Devprayag) that are consistent with the expected thinning rates.     

Risk assessment of soil erosion in semi-arid mountainous watershed in Saudi Arabia by RUSLE model coupled with remote sensing and GIS

Soil erosion is the most important factor in land degradation and influences desertification in semi-arid areas. A comprehensive methodology that integrates revised universal soil loss equation (RUSLE) model and GIS was adopted to determine the soil erosion risk (SER) in semi-arid Aseer region, Saudi Arabia. Geoenvironmental factors viz. rainfall (R), soil erodibility (K), slope (LS), cover management and practice factors were computed to determine their effects on average annual soil loss. The high potential soil erosion, resulting from high denuded slope, devoid of vegetation cover and high intensity rainfall, is located towards the north western part of the study area. The analysis is investigated that the SER over the vegetation cover including dense vegetation, sparse vegetation and bushes increases with the higher altitude and higher slope angle. The erosion maps generated with RUSLE integrated with GIS can serve as effective inputs in deriving strategies for land planning/management in the environmentally sensitive mountainous areas.     

Rationalization of building micro-dams equipped with fish passages in West African savannas

Micro-dams in West African savannas are investigated in conjunction with aquatic fauna and human activities at a community level. A study area is chosen in the Northern Region of Ghana. The micro-dams in the study area serve as habitats for fish, providing food and job opportunities for inhabitants, but their construction has sacrificed rice fields and fragmented migration routes of fish. A stochastic population dynamics model is developed to rigorously assess the effect of establishing fish passages between the fragmented habitats containing the micro-dams on the ichthyological fauna. Values of the model parameters are estimated from the literature and results of field surveys, in which ten fish species including cichlidae, clariidae, bagridae, schilbeidae, cyprinidae, and alistidae are reported to be present. A sustainability criterion is proposed to judge whether a set of model parameters realizes stationarity of the stochastic process representing the population dynamics. It is suggested that ichthyological fauna can be sustainable provided that the fishing activity is restricted to upstream migrating and fast growing species. More generally, building micro-dams in West African savannas will be much better justified when the dams are equipped with appropriately designed fish passages.     

The response of the upper ocean to tropical cyclone Viyaru over the Bay of Bengal

Better forecast of tropical cyclone(TC) can help to reduce risk and enhance management. The TC forecast depends on the scientific understanding of oceanic processes, air-sea interaction and finally, the atmospheric process. The TC Viyaru is taken as an example, which is formed at the end of 11 May 2013 and sustains up to 17 May 2013 during pre-monsoon season. Argo data are used to investigate ocean response processes by comparing pre-and post-conditions of the TC. Eight oceanic parameters including the sea surface temperature(SST), the sea surface salinity(SSS), and the barrier layer thickness(BLT), the 26°C isotherm depth in the ocean(D26), the isothermal layer depth(ILD), the mixed layer depth(MLD), the tropical cyclone heat potential(TCHP) and the effective oceanic layer for cyclogenesis(EOLC) are chosen to evaluate the pre-and post-conditions of the TC along the track of Viyaru. The values of the SST, D26, BLT, TCHP and EOLC in the pre-cyclonic condition are higher than the post-cyclonic condition, while the SSS, ILD and MLD in the post-cyclonic condition are higher than the pre-cyclonic condition of the ocean due to strong cyclonic winds and subsurface upwelling. It is interesting that the strong intensity of the TC reduces less SST and vice versa. The satisfied real time Argo data is not available in the northern Bay of Bengal especially in the coastal region. A weather research and forecasting model is employed to hindcast the track of Viyaru, and the satellite data from the National Center Environmental Prediction are used to assess the hindcast.     

Stochastic control of a micro-dam irrigation scheme for dry season farming

Micro-dams are expected to be feasible options for water resources development in semi-arid regions such as the Guinea savanna agro-ecological zone of West Africa. An optimal water management strategy in a micro-dam irrigation scheme supplying water from an existing reservoir to a potential command area is discussed in this paper based on the framework of stochastic control. Water intake facilities are assumed to consist of photovoltaic pumping system units and hoses. The knowledge of current states of the storage volume of the reservoir and the soil moisture in the command area is fed-back to the intake flow rate. A system of two stochastic differential equations is proposed as a model for the dynamics of the micro-dam irrigation scheme, so that temporally backward solution of the Hamilton–Jacobi–Bellman equation determines an optimal control, which represents the optimal water management strategy. A computational procedure using the finite element method is successfully implemented to provide comprehensive information on the optimal control. The results indicate that the water initially stored in the reservoir can support full irrigation for about 80 days under the optimal water management strategy, which is predominantly based on the demand-side principle. However, the volatility of the soil moisture in the command area must be reasonably small.     

Changes in monsoon precipitation patterns over Bangladesh and its teleconnections with global climate

Theoretical and Applied Climatology - Understanding changes in monsoon precipitation patterns is crucial as it determines the occurrence, intensity, and duration of floods and droughts in...     

Liquefaction resistance evaluation of soils using artificial neural network for Dhaka City,Bangladesh

Natural Hazards - Soil liquefaction resistance evaluation is an important site investigation for seismically active areas. To minimize the loss of life and property, liquefaction hazard analysis is...     

Sedimentological and petrochemical studies of Jurassic clastic rocks,Habo Dome Basin,Kachchh Mainland,Northwest India: Implications for depositional environment,provenance, and tectonic setting

Mesozoic rocks are extensively and excellently preserved in the western Indian shield in several basins. The Kachchh Mainland Basin (KMB), comprising six small sub‐basins, is the main repository of these sediments. Habo Dome Basin, situated in the easternmost part of KMB and largest among the six basins, hosts clastics of the Chari Formation of Jurassic age. The fluctuating transgressive–regressive facies cycle, developed during the Callovian and Late Early Oxfordian in the Habo Dome Basin, was mainly controlled by local tectonics and not by global eustatic fluctuations. Near magmatic relationships are displayed by various elements of the clastic rocks of Habo Dome Basin. Two litho‐chemical groups have been identified in Habo Dome Basin, which are cyclically repeated over entire lithostratigraphic sequence, indicating alternate pulses of sediment inputs from two different sources under palpitating tectonic conditions. Provenance indicator elements and their ratios coupled with source modeling indicate predominantly felsic source with basic and alkalic components. Integrated analysis of petrograhic and geochemical characteristics suggests two source terranes for these rocks: a granitoid source with significant basic volcanics (Banded Gneissic Complex) and a granite–gneissic source with minor alkaline volcanics (Nagarparkar Massif) lying to northeast and NNW respectively. The petrochemistry of Habo Dome clastics suggests their deposition in a fault controlled sink which was influenced by sea level changes. Drifting of the Indian plate resulted in the opening of series of rifted basins in the Kachchh Mainland during Late Triassic/Early Jurassic, which were closed later during collision of Indian plate with Eurasia at early Eocene. The Habo Dome Basin which opened up as a half graben in response to the initial stress regime, remained tectonically unstable until the cessation of pre and post collisional stress regimes.     

A stochastic differential equation model for assessing drought and flood risks

Droughts and floods are two opposite but related hydrological events. They both lie at the extremes of rainfall intensity when the period of that intensity is measured over long intervals. This paper presents a new concept based on stochastic calculus to assess the risk of both droughts and floods. An extended definition of rainfall intensity is applied to point rainfall to simultaneously deal with high intensity storms and dry spells. The mean-reverting Ornstein–Uhlenbeck process, which is a stochastic differential equation model, simulates the behavior of point rainfall evolving not over time, but instead with cumulative rainfall depth. Coefficients of the polynomial functions that approximate the model parameters are identified from observed raingauge data using the least squares method. The probability that neither drought nor flood occurs until the cumulative rainfall depth reaches a given value requires solving a Dirichlet problem for the backward Kolmogorov equation associated with the stochastic differential equation. A numerical model is developed to compute that probability, using the finite element method with an effective upwind discretization scheme. Applicability of the model is demonstrated at three raingauge sites located in Ghana, where rainfed subsistence farming is the dominant practice in a variety of tropical climates.