JBA Consulting Engineers and Scientists

Skipton, United Kingdom

JBA Consulting Engineers and Scientists

Skipton, United Kingdom
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Sharif M.,Jamia Millia Islamia University | Archer D.R.,JBA Consulting Engineers and Scientists | Fowler H.J.,Newcastle University | Forsythe N.,Newcastle University
Hydrology and Earth System Sciences | Year: 2013

River flow is a reflection of the input of moisture and its transformation in storage and transmission over the catchment. In the Upper Indus Basin (UIB), since high-altitude climate measurement and observations of glacier mass balance are weak or absent, analysis of trends in magnitude and timing in river flow provides a window on trends and fluctuations in climate and glacier outflow. Trend analysis is carried out using a Mann-Kendall nonparametric trend test on records extending from 1960 to 1998. High-level glacial catchments show a falling trend in runoff magnitude and a declining proportion of glacial contribution to the main stem of the Indus. Elsewhere annual flow has predominantly increased with several stations exhibiting statistically significant positive trends. Analysis of timing using spring onset date (SOT) and centre of volume date (CoV) indicated no clear trends-in direct contrast to what has been observed in western North America. There is, however, a consistent relationship between CoV and annual runoff volume. A consistently positive correlation was also found between SOT and CoV for all the stations, implying that initial snowpack conditions before the onset of runoff influence timing throughout the season. The results of the analysis presented here indicate that the magnitude and timing of streamflow hydrograph is influenced both by the initial snowpack and by seasonally varied trends in temperature. The study contributes to the understanding of the links between climate trends and variability and river runoff and glacier mass balance and runoff. The Upper Indus Basin is predominantly influenced by winter precipitation; similar trend analysis applied to summer-monsoon-dominated catchments of the central Himalaya is recommended. © 2013 Author(s).

Sharif M.,Jamia Millia Islamia University | Archer D.,JBA Consulting Engineers and Scientists | Hamid A.T.,University of Mosul
World Environmental and Water Resources Congress 2012: Crossing Boundaries, Proceedings of the 2012 Congress | Year: 2012

Most operational decisions for water resources infrastructure are dependent on both the timing and magnitude of flows, and therefore climate change impact assessment must consider both these characteristics. This paper examines trends in the magnitude and timings of streamflow at several stations in Satluj River basin in India. The intention is to increase the reliability of water resources systems in the basin through consideration of the observed trends. The Mann-Kendall nonparametric trend test, incorporating a correction for serial correlation and presence of ties, was used for the detection of trends. Trends in seasonal proportions of annual flow as well as actual flows have been investigated. Timings of extreme flows at several locations in the basin have also been investigated. The results reveal more trends than would be expected to occur by chance for several of the magnitude and timing measures considered in this study. The contribution of glacier melt to annual runoff at Bhakra, the major reservoir in the basin, is approximately 59% and therefore any changes in magnitude and timings of water availability at the reservoir could have significant implications for its operation. Further, climate change induced changes in the timings and magnitude of water availability at Bhakra, the major reservoir in the basin, could put the drinking water supplies of millions of people at risk. The study will contribute towards climate change modeling efforts being undertaken in a climatologically sensitive basin such as Satluj. © 1012 ASCE.

Forsythe N.,Newcastle University | Hardy A.J.,Aberystwyth University | Fowler H.J.,Newcastle University | Blenkinsop S.,Newcastle University | And 3 more authors.
Journal of Climate | Year: 2015

Clouds play a key role in hydroclimatological variability by modulating the surface energy balance and air temperature. This study utilizes MODIS cloud cover data, with corroboration from global meteorological reanalysis (ERA-Interim) cloud estimates, to describe a cloud climatology for the upper Indus River basin. It has specific focus on tributary catchments in the northwest of the region, which contribute a large fraction of basin annual runoff, including 65% of flow originating above Besham, Pakistan or 50 km3 yr-1 in absolute terms. In this region there is substantial cloud cover throughout the year, with spatial means of 50%-80% depending on the season. The annual cycles of catchment spatial mean daytime and nighttime cloud cover fraction are very similar. This regional diurnal homogeneity belies substantial spatial variability, particularly along seasonally varying vertical profiles (based on surface elevation). Correlations between local near-surface air temperature observations and MODIS cloud cover fraction confirm the strong linkages between local atmospheric conditions and near-surface climate variability. These correlations are interpreted in terms of seasonal and diurnal variations in apparent cloud radiative effect and its influence on near-surface air temperature in the region. The potential role of cloud radiative effect in recognized seasonally and diurnally asymmetrical temperature trends over recent decades is also assessed by relating these locally observed trends to ERA-Interim-derived trends in cloud cover fraction. Specifically, reduction in nighttime cloud cover fraction relative to daytime conditions over recent decades appears to provide a plausible physical mechanismfor the observed nighttime cooling of surface air temperature in summermonths. © 2015 American Meteorological Society.

Forsythe N.,Newcastle University | Fowler H.J.,Newcastle University | Blenkinsop S.,Newcastle University | Burton A.,Newcastle University | And 4 more authors.
Journal of Hydrology | Year: 2014

Assessing local climate change impacts requires downscaling from Global Climate Model simulations. Here, a stochastic rainfall model (RainSim) combined with a rainfall conditioned weather generator (CRU WG) have been successfully applied in a semi-arid mountain climate, for part of the Upper Indus Basin (UIB), for point stations at a daily time-step to explore climate change impacts. Validation of the simulated time-series against observations (1961-1990) demonstrated the models' skill in reproducing climatological means of core variables with monthly RMSE of <2.0. mm for precipitation and ≤0.4. °C for mean temperature and daily temperature range. This level of performance is impressive given complexity of climate processes operating in this mountainous context at the boundary between monsoonal and mid-latitude (westerly) weather systems. Of equal importance the model captures well the observed interannual variability as quantified by the first and last decile of 30-year climatic periods.Differences between a control (1961-1990) and future (2071-2100) regional climate model (RCM) time-slice experiment were then used to provide change factors which could be applied within the rainfall and weather models to produce perturbed 'future' weather time-series. These project year-round increases in precipitation (maximum seasonal mean change:+27%, annual mean change: +18%) with increased intensity in the wettest months (February, March, April) and year-round increases in mean temperature (annual mean +4.8. °C). Climatic constraints on the productivity of natural resource-dependent systems were also assessed using relevant indices from the European Climate Assessment (ECA) and indicate potential future risk to water resources and local agriculture.However, the uniformity of projected temperature increases is in stark contrast to recent seasonally asymmetrical trends in observations, so an alternative scenario of extrapolated trends was also explored. We conclude that interannual variability in climate will continue to have the dominant impact on water resources management whichever trajectory is followed. This demonstrates the need for sophisticated downscaling methods which can evaluate changes in variability and sequencing of events to explore climate change impacts in this region. © 2014.

Bendall B.,Lowestoft Laboratory | Moore A.,Lowestoft Laboratory | Maxwell D.,Lowestoft Laboratory | Davison P.,Lowestoft Laboratory | And 6 more authors.
Fisheries Management and Ecology | Year: 2012

Advances the field of telemetry techniques during the last few decades have greatly expanded our knowledge on migratory behaviour and provided the opportunity to obtapractically useful data for the conservation and management of salmonid populations. However, applying this information to the development of much needed population-based migration models has been limited. Furthermore, this research has generally been restricted to assessing the role of river flow on fish movement. Models derived from a 6-year telemetry study on the movements of Atlantic salmon, Salmo salar L., and sea trout, Salmo trutta L., the River Tyne are presented together with an assessment of counter data from the same river to highlight the importance of additional environmental and physiological parameters regulating fish movement. The data are discussed relation to the advantages of telemetry data, the need to develop predictive models, the statistical methods used and the potential direction of future work this area. © 2011 Crown copyright.

Rameshwaran P.,UK Center for Ecology and Hydrology | Naden P.S.,UK Center for Ecology and Hydrology | Lawless M.,JBA Consulting Engineers and Scientists
Earth Surface Processes and Landforms | Year: 2011

A key problem in computational fluid dynamics (CFD) modelling of gravel-bed rivers is the representation of multi-scale roughness, which spans the range from grain size, through bedforms, to channel topography. These different elements of roughness do not clearly map onto a model mesh and use of simple grain-scale roughness parameters may create numerical problems. This paper presents CFD simulations for three cases: a plane bed of fine gravel, a plane bed of fine gravel including large, widely-spaced pebble clusters, and a plane gravel bed with smaller, more frequent, protruding elements. The plane bed of fine gravel is modelled using the conventional wall function approach. The plane bed of fine gravel including large, widely-spaced pebble clusters is modelled using the wall function coupled with an explicit high-resolution topographic representation of the pebble clusters. In these cases, the three-dimensional Reynolds-averaged continuity and Navier-Stokes equations are solved using the standard k-ε turbulence model, and model performance is assessed by comparing predicted results with experimental data. For gravel-bed rivers in the field, it is generally impractical to map the bed topography in sufficient detail to enable the use of an explicit high-resolution topography. Accordingly, an alternative model based on double-averaging is developed. Here, the flow calculations are performed by solving the three-dimensional double-averaged continuity and Navier-Stokes equations with the spatially-averaged 〈k-ε〉 turbulence model. For the plane bed of fine gravel including large, widely-spaced pebble clusters, the model performance is assessed by comparing the spatially-averaged velocity with the experimental data. The case of a plane gravel bed with smaller, more frequent, protruding elements is represented by a series of idealized hypothetical cases. Here, the spatially-averaged velocity and eddy viscosity are used to investigate the applicability of the model, compared with using the explicit high-resolution topography. The results show the ability of the model to capture the spatially-averaged flow field and, thus, illustrate its potential for representing flow processes in natural gravel-bed rivers. Finally, practical data requirements for implementing such a model for a field example are given. © 2011 John Wiley & Sons, Ltd.

Archer D.R.,JBA Consulting Engineers and Scientists | Climent-Soler D.,Cranfield University | Holman I.P.,Cranfield University
Hydrology Research | Year: 2010

Despite substantial evidence that land use and management can enhance flood runoff at a local scale, evidence of increased flood risk based on peak discharges is lacking in catchments greater than 10 km2. This analysis is instead based on assessing changes in short-term rates of change in discharge. The influence of land use is demonstrated first on the small Coalburn catchment where changes in rates of rise are closely related to drainage and afforestation. For the larger Axe catchment (288 km2), changes in rates of rise are investigated by comparing annual maximum and peaks over a threshold flows for different periods, by comparing rates of rise associated with given daily rainfall and by adapting the method of flow variability analysis for use of rates of change rather than flow itself. All these methods demonstrate significant changes in river flow dynamics which seem to be in parallel with land use changes even when the influence of climate variability from year to year has been taken into account. Rates of change in discharge appear to respond to land use changes and thus provide a potential basis for application to land use management policies. © IWA Publishing 2010.

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