Desert riparian forest colonization in the lower reaches of Tarim River based on remote sensing analysis

The ecological water conveyance project that pipes water from Daxihaizi reservoir to lower reaches of Tarim River has been implemented ten times since 2000. After ecological water conveyance, restoration has taken place for vegetation along the dried-up lower reaches of the Tarim River. The changes of vegetation fluctuated yearly due to ecological water conveyance. In order to reveal the detailed process of vegetation changes, remote sensing images from 1999 to 2010 were all classified individually into vegetated and non-vegetated areas using the soil-adjusted vegetation index threshold method. Then inter-annual changes of vegetation over a period of 12 years were obtained using a post-classification change detection technique. Finally, spatial–temporal changes distribution of vegetation cover and its response to ecological water conveyance were analyzed. The results indicate: (1) vegetation area increased by 8.52 % overall after ecological water conveyance. Vegetation between 2003 and 2004 increased dramatically with 45.87 % while vegetation between 2002 and 2003 decreased dramatically with 17.83 %. (2) Vegetation area gain is greater than vegetation loss during 1999–2000, 2001–2002, 2003–2004 and 2009–2010 periods. Although vegetation restoration is obvious from 1999 to 2010, vegetation loss also existed except for the periods above. It indicates that vegetation restoration fluctuated due to ecological water conveyance. (3) Spatial distribution of vegetation restoration presented “strip” distribution along the river and group shaper in the lower terrain area, while spatial distribution of vegetation loss mainly located in the upper reaches of river and area far away from the river. (4) Vegetation restoration area had a positive relative with total ecological water conveyance volume. The scheme and season of ecological water conveyance had also influenced the vegetation restoration. The vegetation change process monitoring, based on continuous remote sensing data, can provide the spatial–temporal distribution of vegetation cover in a large-scale area and scientific evidences for implementing ecological water conveyance in the lower Tarim River.     

Investigating a reservoir bank slope displacement history with multi-frequency satellite SAR data

Slope instability arisen along with dam construction is a common problem of great concern in reservoir areas. Thus, displacement monitoring of active slopes is of great importance for the safety of dam operation. The unstable Guobu slope is located only about 1.5 km away from Laxiwa hydropower station in upstream Yellow River. In this study, Synthetic Aperture Radar (SAR) datasets acquired by C-band Environmental Satellite (ENVISAT) Advanced Synthetic Aperture Radar (ASAR), L-band Advanced Land Observing Satellite 2 (ALOS-2) Phased Array type L-band Synthetic Aperture Radar 2 (PALSAR-2), and X-band TerraSAR-X covering different evolution stages of Guobu slope were collected to investigate the displacement history so as to facilitate understanding of its deformation and failure mechanisms. The displacements occurred during the past decade were quantitatively identified for the first time by SAR pixel offset tracking analyses. The results show that before the reservoir impoundment, the maximum accumulative displacements on the slope were more than 7 m from 2003 to 2008, while the post-impoundment displacements also exceeded 7 m in just 1 year from September 2009 to September 2010. Furthermore, this slope is still in active deformation up to now. Nevertheless, the displacement rates seem decreased recently according to the interferometric results of TerraSAR-X data pairs from September 2015 to March 2016.     

Impact of period and timescale of FDDA analysis nudging on the numerical simulation of tropical cyclones in the Bay of Bengal

In this study, the impact of four-dimensional data assimilation (FDDA) analysis nudging is examined on the prediction of tropical cyclones (TC) in the Bay of Bengal to determine the optimum period and timescale of nudging. Six TCs (SIDR: November 13–16, 2007; NARGIS: April 29–May 02, 2008; NISHA: November 25–28, 2008; AILA: May 23–26, 2009; LAILA: May 18–21, 2010; JAL: November 04–07, 2010) were simulated with a doubly nested Weather Research and Forecasting (WRF) model with a horizontal resolution of 9 km in the inner domain. In the control run for each cyclone, the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) analysis and forecasts at 0.5° resolution are used for initial and boundary conditions. In the FDDA experiments available surface, upper air observations obtained from NCEP Atmospheric Data Project (ADP) data sets were used for assimilation after merging with the first guess through objective analysis procedure. Analysis nudging experiments with different nudging periods (6, 12, 18, and 24 h) indicated a period of 18 or 24 h of nudging during the pre-forecast stage provides maximum impact on simulations in terms of minimum track and intensity forecasts. To determine the optimum timescale of nudging, two cyclone cases (NARGIS: April 28–May 02, 2008; NISHA: November 25–28, 2008) were simulated varying the inverse timescales as 1.0e?4 to 5.0e?4 s^?1 in steps of 1.0e?4 s^?1. A positive impact of assimilation is found on the simulated characteristics with a nudging coefficient of either 3.0e?4 or 4.0e?4 s^?1 which corresponds to a timescale of about 1 h for nudging dynamic (u,v) and thermodynamical (t,q) fields.     

Evaluation of rainfall and wetland water area variability at Thirlmere Lakes using Landsat time-series data

Thirlmere Lakes is a group of five freshwater wetlands in the southwest fringe of Sydney, Australia, that is subject to cyclic wetting and drying. The lakes are surrounded by activities that have led to increasing pressure on the local surface and groundwater supply including farming and mining. The mine has been operating for more than 30 years, and in recent times, there has been speculation that the surface subsidence and underground pumping may have some impact on surface water and groundwater hydrology. A study was undertaken using satellite imagery to examine the relation between water area changes and rainfall variability. The study utilised Landsat time-series data during the period 1982–2014 to calculate changes in the lake water area (LA), through the normalised difference water index (NDWI) threshold. High classification accuracy was achieved using NDWI against high-resolution data that are available for the years 2008 (88.4 %), 2010 (92.8 %), and 2013 (96.9 %). The LA measurement was correlated against 11 historic observations that occurred in 2009, 2010, and 2011 during drier wetland conditions. Correlation analysis of the LA with the residual rainfall mass spread across the past 30 years has found that rainfall variability is a major dominant factor associated with the wetland changes. The underground mining operations, if verified by independent investigations, probably play a minor or negligible contributor to variations in total wetland area during the study period. This study has demonstrated that remote sensing is a technique that can be used to augment limited historic data.     

Spatial change detection of glacial lakes in the Koshi River Basin,the Central Himalayas

Region warming and the resulting ongoing deglaciation have led to the formation of new glacial lakes and expansion of existing glacial lakes. For giving an overview of the distribution and expansion of glacial lakes in the Koshi River Basin (KRB) between the Central China and Nepal Himalayas in the recent 10 years, this paper aimed to analyze and assess recent spatial variability of glacial lake changes in the KRB, Central Himalayas using two inventory data of glacial lake in 2001 and 2010 in Nepal and Landsat TM/ETM+ data for the 1990s, 2000 and 2009 on the Chinese section of the KRB. The datasets show that there are 1,203 glacial lakes with a total area of 118.54 km² in the KRB in 2009, in which 599 lakes are mapped in the Nepalese section of the KRB with a total of 25.92 km², and 604 lakes in the Chinese section of the KRB with a total area of 92.62 km². From 2000 to 2009, the total number of glacial lakes decreased from 1,668 to 1,203 with a reduction of 45.86 % in the KRB, whereas the total lake areas expanded by 10.60 % (i.e. 0.72 km²/a), from 111.35 to 118.54 km² between 2000, 2001 and 2009, 2010. Especially, 17 lakes are identified as potentially dangerous glacial lakes (PDGLs) by International Centre for Integrated Mountain Development (ICIMOD) on the Nepalese section of the KRB in 2009. In the same period, 23 PDGLs are also identified on the Chinese section of the KRB and the total area increased by 77.46 % (i.e. 0.37 km²/a) from 1990 to 2010 and the expansion rate is significantly higher than 39 % (0.19 km²/a) of non-PDGLs. Therefore, there is a need for promoting the awareness of the hazard potential of glacier lakes to support proper planning of mitigation and adaptation strategies in this context.     

Thermal, mechanical and chemical influences on the performance of optical fibres for distributed temperature sensing in a hot geothermal well

Structural well-bore integrity is an important issue for sustainable provision of geothermal energy. Raman scattering based fibre optic distributed temperature sensing (DTS) can help to monitor the status of a well and therefore help to optimize expensive work-over activities. This study reports on the installation of a fibre-optic cable in the cemented annulus behind the anchor casing in the high temperature geothermal well HE-53, Hellisheiði geothermal field, SW Iceland. Although the cable has been damaged during the installation, temperature data could be acquired during the entire length of installation down to 261.3 m. Temperature measurements were performed during the installation in spring 2009, during the onset of a flow test in summer 2009 and after a 8.5 month shut-in period in summer 2010. During the flow test, maximum temperatures of 230 °C were measured after 2 weeks fluid production. Using optical time domain reflectometry (OTDR), attenuation measurements at 850 and 1,300 nm enabled to identify mechanical, thermal, and chemical degradation along the optical fibre. The observed degradation led to erroneous temperature readings and limits, due to the optical budget of the DTS system, the accessible length of the fibre. The characteristics and the influence of the different degradation mechanisms on the accuracy of the DTS measurements are discussed and recommendations for an optimized installation are given.     

A new artificial oasis landscape dynamics in semi-arid Hongsipu region with decadal agricultural irrigation development in Ning Xia,China

Understanding the ecological mechanisms and processes driving changes in our landscapes is significant for ecological conservation. This work used remote sensing with the extending contingency-based method to quantify the interchange relationship of land use types, and landscape metrics including spatially nuanced difference at patch level to track immigrants’ resettlement impacts at the semi-arid Hongsipu region with decadal agricultural pumping irrigation development in Ning Xia, China. Landsat-TM images acquired in 1989, 1999, 2003, and 2008 were used to study landscape changes in three periods, the earlier development from 1989 to 1999, the middle period in 1999–2003, and final stage in 2003–2008. The results showed the over 50 % landscape area experienced drastic change in each period with heavy immigrants’ perturbations since 1998. The nearly natural landscape with 1:1 area between desert and steppe in 1989 10 years before development, however, became the overwhelming barren landscape with almost 80 % of the study area in 2008, grassland and shrub land almost disappeared respectively, and cultivated land climbed to the third large type from about 2 % in 1989 to more than 16 % in 2008. The landscape became more fragmented, more regular shape with human disturbance spreading from the northwest low mountain and flat basin to the southeast diluvial fan, even high mountain at the end. Although Hongsipu pumping irrigation zone alleviates poor population pressure in the fragile ecological southern mountainous areas of Ningxia, the new artificial oasis creates another possible new ecological risk of the study area. Therefore, besides the economic development, the ecological conservation and restoration measures should be also the primary objectives in order to successful resettlement immigrants.     

Geophysical characterization of the lithological control on the kinematic pattern in a large clayey landslide (Avignonet,French Alps)

Lithology variation is known to have a major control on landslide kinematics, but this effect may remain unnoticed due to low spatial coverage during investigation. The large clayey Avignonet landslide (French Alps) has been widely studied for more than 35 years. Displacement measurements at 38 geodetic stations over the landslide showed that the slide surface velocity dramatically increases below an elevation of about 700 m and that the more active zones are located at the bottom and the south of the landslide. Most of the geotechnical investigation was carried out in the southern part of the landslide where housing development occurred on lacustrine clay layers. In this study, new electrical prospecting all across the unstable area revealed the unexpected presence of a thick resistive layer covering the more elevated area and overlying the laminated clays, which is interpreted as the lower part of moraine deposits. The downslope lithological boundary of this layer was found at around 700 m asl. This boundary coincides with the observed changes in slide velocity and in surface roughness values computed from a LiDAR DTM acquired in 2006. This thick permeable upper layer constitutes a water reservoir, which is likely to influence the hydromechanical mechanism of the landslide. The study suggests a major control of vertical lithological variations on the landslide kinematics, which is highlighted by the relation between slide velocity and electrical resistivity.     

Spatial and temporal variability of soil moisture based on multifractal analysis

Based on the experimental data collected from 2002 to 2010 in Jilin province, we performed multifractal analysis to investigate the spatial variability of soil moisture during 9 years from 2002 to 2010 and about 60 days from April 21 to June 21 in 2010, and analyzed the relationship between soil moisture and precipitation. The results showed that the soil moisture was multifractal. It was intermediate variability in the soil sample. From 2002 to 2010, the spatial variation of soil moisture was charactered by long distance in 2004, 2006, and 2009 and short distance in 2002, 2003, and 2008. The spatial variation of soil moisture was charactered by long distance from April 21 to May 11 and late June. It was charactered by short distance from May 11 to June 21. From April 11 to July 1, 2010, the spatial variation of soil moisture was mainly affected by the spatial variation of precipitation. From 2002 to 2010, the spatial variation of soil moisture was mainly affected by precipitation in 2006, 2009, and 2010. The spatial variation of precipitation had little effect on soil moisture during 2002 to 2005 and 2007 to 2008. This study analyzed the multifractal characteristic of soil moisture from the perspective of water resources divisions, which can provide references for soil water resources evaluation and water resources allocation.     

Optical Changes in a Eutrophic Estuary During Reduced Nutrient Loadings

Loss of water clarity is one of the consequences of coastal eutrophication. Efforts have therefore been made to reduce external nutrient loadings of coastal waters. This paper documents improvements to water clarity between 1985 and 2008–2009 at four stations in the microtidal estuary Roskilde Fjord and find significant relationships to freshwater nutrient loadings. The paper then investigates to which extent changes in phytoplankton biomass (chlorophyll a (Chl a)), non-algal particulate organic matter (POM*), and residual attenuation in the water (K _b), respectively, can account for this optical improvement. Vertical light attenuation (K _d) declined, on average, by 34 %, accompanying a 71 % reduction of Chl a and an 80 % reduction of POM*. Residual attenuation declined by 26 % over the period in accordance with a measured 34 % decline of dissolved organic nitrogen. Analysis of simultaneous changes in light attenuation and Secchi depth also suggested a reduction of the scatter-to-absorption ratio over time. Considering the stronger reductions of particle concentrations than dissolved organic matter, the contribution of residual attenuation to vertical attenuation increased from 54 to 74 % in 1985 to 78 to 85 % in 2008–2009. Overall, efforts to reduce nutrient loading and improve water clarity appeared to have had a larger impact on POM* than on Chl a and colored dissolved organic matter concentrations in the estuary, which can account for the decrease in the scatter-to-absorption ratio. These optical changes lead to larger improvements of Secchi depth than of vertical light attenuation. The consequence of this is an overestimation (0.45–1.48 m) of the predicted increase of potential seagrass depth limits when based on Secchi depth rather than K _d.     

Measuring displacements of the Thompson River valley landslides,south of Ashcroft,BC, Canada,using satellite InSAR

The Thompson River valley, south of Ashcroft in British Columbia, Canada, has experienced several landslides since the mid-1800s. The national railways that run along the valley cross a number of these landslides. All the landslides occur in glacial deposits, typically sliding on weak clay layers. Some have failed rapidly to very rapidly and are currently inactive or showing deformation rates from a few millimeters to centimeters per year. An evaluation of satellite InSAR (Interferometric Synthetic Aperture Radar) using RADARSAT-2 images between September 2013 and November 2015 provides new insight into landslide displacements in the Thompson River valley. This information enhances the ongoing hazard management of unstable terrain. This paper presents the comparison of the InSAR measurements with other instrumentation (GPS and ShapeAccelArrays? -SAA) installed at one moving landslide and then addresses the extent and magnitude of the slope movements observed. InSAR was found to provide similar displacement values to those measured otherwise. The stable location showed displacements of +/?1 mm with an average near zero during the whole monitoring period. Six areas of slope movement were identified within the study area, all within or adjacent to the footprints of past landslides. The average line of sight (LOS) displacement rates range between 11 and 39 mm/year. Most of the landslides exhibited seasonal variations in velocity that corresponds to changes in river elevation in the valley.     

Large slope deformations detection and monitoring along shores of the Potrerillos dam reservoir,Argentina, based on a small-baseline InSAR approach

The Argentina National Road 7 that crosses the Andes Cordillera within the Mendoza province to connect Santiago de Chile and Buenos Aires is particularly affected by natural hazards requiring risk management. Integrated in a research plan that intends to produce landslide susceptibility maps, we aimed in this study to detect large slope movements by applying a satellite radar interferometric analysis using Envisat data, acquired between 2005 and 2010. We were finally able to identify two large slope deformations in sandstone and clay deposits along gentle shores of the Potrerillos dam reservoir, with cumulated displacements higher than 25 mm in 5 years and towards the reservoir. There is also a body of evidences that these large slope deformations are actually influenced by the seasonal reservoir level variations. This study shows that very detailed information, such as surface displacements and above all water level variation, can be extracted from spaceborne remote sensing techniques; nevertheless, the limitations of InSAR for the present dataset are discussed here. Such analysis can then lead to further field investigations to understand more precisely the destabilising processes acting on these slope deformations.     

Activity and kinematic behaviour of deep-seated landslides from PS-InSAR displacement rate measurements

Large landslides and deep-seated gravitational slope deformations (DSGSD) represent an important geo-hazard in relation to the deformation of large structures and infrastructures and to the associated secondary landslides. DSGSD movements, although slow (from a few millimetres to several centimetres per year), can continue for very long periods, producing large cumulative displacements and undergoing partial or complete reactivation. Therefore, it is important to map the activity of such phenomena at a regional scale. Ground surface displacements at DSGSD typically range close to the detection limit of monitoring equipment but are suitable for synthetic aperture radar (SAR) interferometry. In this paper, permanent scatterers (PSInSAR?) and SqueeSAR? techniques are used to analyse the activity of 133 DSGSD, in the Central Italian Alps. Statistical indicators for assigning a degree of activity to slope movements from displacement rates are discussed together with methods for analysing the movement and activity distribution within each landslide. In order to assess if a landslide is active or not, with a certain degree of reliability, three indicators are considered as optimal: the mean displacement rate, the activity index (ratio of active PS, displacement rate larger than standard deviation, overall PS) and the nearest neighbor ratio, which allows to describe the degree of clustering of the PS data. According to these criteria, 66% of the phenomena are classified as active in the monitored period 1992–2009. Finally, a new methodology for the use of SAR interferometry data to attain a classification of landslide kinematic behaviour is presented. This methodology is based on the interpretation of longitudinal ground surface displacement rate profiles in the light of numerical simulations of simplified failure geometries. The most common kinematic behaviour is rotational, amounting to 41 DSGSDs, corresponding to the 62.1% of the active phenomena.     

Site scale modeling of slow-moving landslides,a 3D viscoplastic finite element modeling approach

This paper presents an advanced 3D numerical methodology to reproduce the kinematics of slow active landslides, more precisely, to reproduce the nearly constant strain rate (secondary creep) and the acceleration/deceleration of the moving mass due to hydrological changes. For this purpose, finite element analyses are performed in a large area covering a long time-span (12 years), in order to exhibit different interacting slope movements. First, we perform a stability analysis using the shear strength reduction (SSR) technique with a Mohr-Coulomb failure criteria. It is done in order to compute factors of safety (FS) and to identify two different scenarios, the first one being stable (FS > 1) and the second one being unstable (FS < 1). In the studied test case, the Portalet landslide (Central Spanish Pyrenees), the first scenario corresponds to an initial stable configuration of the slope and the second one to an unstable excavated configuration. Second, taking the first scenario as an initial condition, a time-dependent analysis is performed using a coupled formulation to model solid skeleton and pore fluids interaction, and a simplified ground water model that takes into account daily rainfall intensity. In this case, a viscoplastic constitutive model based on Perzyna’s theory is applied to reproduce soil viscous behavior and the delayed creep deformation due to the excavation. The fluidity parameter is calibrated to reproduce displacements measured by the monitoring systems. Our results demonstrate that 3D analyses are preferable to 2D ones for reproducing in a more realistic way the slide behavior. After calibration, the proposed model is able to simulate successfully short- and medium-term predictions during stages of primary and secondary creep.     

Topographic controls on vegetation index in a hilly landscape: a case study in the Jiaodong Peninsula, eastern China

This study examined topographic influence on spatial and temporal variability in the normalized difference vegetation index (NDVI) derived from the Satellite Pour l’Observation de la Terre-Vegetation at the regional and landscape scales in the Jiaodong Peninsula. The generalized additive models were used to quantify the spatial variation of NDVI attributable to local terrain and topographically related variables including altitude, exposure to incoming solar radiation, topographic wetness index, distance to the nearest stream and distance from the coast. NDVI distribution shows significant dependence on topography. The variables explained 38.3 % of variance in NDVI at the peninsula, and 30–45.3 % of variance in NDVI at the woodland, cropland, and grassland landscapes. At the Jiaodong Peninsula scale, NDVI is influenced primarily by distance from the coast. However, topographic wetness index has the most explanatory power for NDVI at the woodland, cropland, and grassland landscapes. Through a statistical nonparametric correlation analysis (Spearman’s r), the study indicates that spatial distribution of NDVI changes during the period 1998–2009 and future change trend of persistence determined by Hurst exponent is closely associated with topography and topography-based attribution. These results highlight the importance of topographic changes at landscape and regional scales as an important control factor on NDVI patterns.     

Assessing the spatiotemporal dynamics of vegetation cover as an indicator of desertification in Egypt using multi-temporal MODIS satellite images

Desertification is the major environmental threat in the arid and semiarid regions. The soil-adjusted vegetation index (SAVI) was used as an indicator to monitor the desertification change in Egypt. A multi-temporal satellite data of moderate-resolution imaging spectroradiometer were used to estimate SAVI and land surface temperature. Also, Global Multi-resolution Terrain Elevation Data 2010 and climatic data were used for the analysis. This research focuses on assessing the trend of the vegetation cover change in the seasons of January, March, June, September, and December for the years 2002, 2005, 2008, and 2011. The magnitude of the vegetation cover change in periods 2002–2005, 2005–2008, and 2008–2011 at ≤100 and >100 m elevation was analyzed. A major increase in the vegetation cover that occurred in the period 2002–2005 was about 3,400 km², as a result of two national megaprojects (Toshka Project and El-Salam Canal). In contrast, vegetation cover decreased by 5,500 km² in March during the period 2005–2008, coinciding with the period when the management of the megaprojects failed. Vegetation cover changed again by 1,500 km² in the period of 2008–2011, and the vegetated areas in the Nile Delta were affected by the sea level rising which was responsible for the soil salinization. Three sites were chosen in this investigation (Kom Ombo, El-Oweinat, and Nile Delta) in order to observe the difference of desertification dynamics and to understand the relationship between the vegetation cover distribution and other environmental variables. Anti-desertification policies and advanced agricultural management are highly required in Egypt to decrease any environmental crises and food shortage.     

Assessment of the mutual impact between climate and vegetation cover using NOAA-AVHRR and Landsat data in Egypt

The objective of the current study is to use satellite data to assess the mutual influence between vegetation and climate. The Ismailia Governorate was selected as a case study to investigate the impact of vegetation cover expansion on both land surface and air temperature from 1983 to 2010 and vice versa. This observation site was carefully selected as a clear example of the high rate of the reclamation and vegetation expansion process in Egypt. Land surface temperature (LST) was estimated through the Advanced Very High Resolution Radiometer (a space-borne sensor embarked on the National Oceanic and Atmospheric Administration) data while air temperature (T _air) was collected from ground meteorological stations in the study area. Irrigated agriculture is the largest consumer of freshwater resources. However, consistent information on irrigation water use is still lacking. Relative humidity, wind speed, solar radiation, and T _air data were inserted in the Penman–Monteith equation to calculate potential evapotranspiration (ET_o), while both LST and T _air were used to observe the relative water status of the study area as a result of the water deficit index (WDI). Then, both WDI and ET_o were used to calculate actual evepotranspiration (ET_C.). The results showed that LST decreased by about 2.3 °C while T _air decreased by about 1.6 °C during the study period. The results showed also that the vegetation cover expanded from 25,529.85 ha in 1985 to 63,140.49 ha in 2009 with about 147 % increase. This decrease in LST and air temperature was according to the expansion of the cultivated land that was proved through the processing of three Landsat TM and Landsat ETM+ imageries acquired in June 19, 1985, June 7, 1998, and June 29, 2009. The vegetation water consumption was affected by the decreasing surface and air temperature. The results showed that the water deficit index decreased by about 0.35, and actual evapotranspiration increased by about 2.5 mm during the study period.     

Analysis of a genesis potential parameter during pre-cyclone watch period over the Bay of Bengal

The genesis potential parameter (GPP) consists of two dynamical variables low-level relative vorticity and vertical wind shear, and two thermodynamic variables middle tropospheric relative humidity and instability are analysed during pre-cyclone watch period over the Bay of Bengal. The pre-cyclone watch period is taken as the period prior to 72-h from the formation of a Depression. The GPP values for 30 tropical disturbances that formed over the Bay of Bengal during the period 2001–2010 are analysed. An independent evaluation of the parameter and possible applications to operational forecasting are presented using data from the year 1998 to 1999. The variables of GPP are calculated using the ECMWF interim reanalysis 1.5° × 1.5° resolution data, averaged within an area of 5° × 5° box on the centre of tropical disturbances and also over the 5° × 5° boxes over the adjacent surrounding areas. The results show that maximum value is observed over the genesis region at 48- and 24-h lead time for both the cases of cyclones and Depressions. The threshold value of GPP is found to be 9.3, 6.3 and 2.7 during pre-cyclone watch period at 24-, 48- and 72-h lead time, respectively. A distinction in GPP values above threshold value for cyclonic and a Depression system is also observed for the cyclogenesis region in 69, 75 and 75 % of cases at 72-, 48- and 24-h lead time, respectively. However, the individual case studies show that the GPP could indicate the genesis of a tropical cyclone with a 2-day lead time. The mean GPP values are 11.8, 8.5 and 3.8 for cyclonic systems and 6.9, 4.2 and 1.6 for Depression systems over an area of a box 5° × 5° on the systems at 24-, 48- and 72-h lead time, respectively, from the stage of Depression. The result of the study is found to be providing probable area of genesis and intensification of a tropical disturbance at a 2 day lead time from the stage Depression.     

Impact analysis of climate change on Kolahoi Glacier in Liddar Valley,north-western Himalayas

Glaciers are among the most conspicuous and dynamic features on the earth’s surface and are also highly sensitive to changes in climatic parameters. Glaciers in the Kashmir Himalayas have been reported to be retreating due to climate forcing. Kolahoi Glacier is one of the largest and important glaciers of the Kashmir Himalayas and is the main source of Liddar River, which is the largest tributary of the Jhelum River system. In the present study, an analysis to assess the response of Kolahoi Glacier to the changing climate was carried out using the Survey of India (SoI) map and multi-temporal Landsat satellite data. The results show a significant change in the spatial extent of Kolahoi Glacier. The total area of this glacier has reduced from 12.21 km² in 1962 to 11.61 km² in 2010. An analysis of meteorological data (temperature and precipitation) shows that the average annual temperature increased from 9.1 °C in 1980–1989 to 10.3 °C in 2000–2009, while the precipitation decreased from 1329.44 to 1126.89 mm during the same period. The results suggest that this glacier will be annihilated completely if the same retreating trend continues.     

Stochastic groundwater modeling of a sedimentary aquifer: evaluation of the impacts of abstraction scenarios under conditions of reduced recharge

A transient finite difference groundwater flow model has been calibrated for the Nasia sub-catchment of the White Volta Basin. This model has been validated through a stochastic parameter randomization process and used to evaluate the impacts of groundwater abstraction scenarios on resource sustainability in the basin. A total of 1500 equally likely model realizations of the same terrain based on 1500 equally likely combinations of the data of the key aquifer input parameters were calibrated and used for the scenario analysis. This was done to evaluate model non-uniqueness arising from uncertainties in the key aquifer parameters especially hydraulic conductivity and recharge by comparing the realizations and statistically determining the degree to which they differ from each other. Parameter standard deviations, computed from the calibrated data of the key parameters of hydraulic conductivity and recharge, were used as a yardstick for evaluating model non-uniqueness. All model realizations suggest horizontal hydraulic conductivity estimates in the range of 0.03–78.4 m/day, although over 70 % of the area has values in the range of 0.03–14 m/day. Low standard deviations of the horizontal hydraulic conductivity estimates from the 1500 solutions suggest that this range adequately reflects the properties of the material in the terrain. Lateral groundwater inflows and outflows appear to constitute significant components of the groundwater budgets in the terrain, although estimated direct vertical recharge from precipitation amounts to about 7 % of annual precipitation. High potential for groundwater development has been suggested in the simulations, corroborating earlier estimates of groundwater recharge. Simulation of groundwater abstraction scenarios suggests that the domain can sustain abstraction rates of up to 200 % of the current estimated abstraction rates of 12,960 m³/day under the current recharge rates. Decreasing groundwater recharge by 10 % over a 20-year period will not significantly alter the results of this abstraction scenario. However, increasing abstraction rates by 300 % over the period with decreasing recharge by 10 % will lead to drastic drawdowns in the hydraulic head over the entire terrain by up to 6 m and could cause reversals of flow in most parts of the terrain.