Hydrology

A model subglacial drainage system, coupled to an ice-dammed reservoir that receives a time-varying meltwater input, is described and analysed. In numerical experiments an ice-marginal lake drains through a subglacial channel, producing periodic floods, and fills with meltwater at a rate
dependent on air temperature, which varies seasonally with a peak value of Tm. The analysis reveals regions of Tm parameter space corresponding to ‘mode locking’, where flood repeat time is independent of Tm; resonance, where decreasing Tm counter-intuitively increases flood size; and chaotic dynamics,
where flood cycles are sensitive to initial conditions, never repeat and exhibit phase-space mixing. Bifurcations associated with abrupt changes in flood size and timing within the year separate these regions. This is the first time these complex dynamics have been displayed by a glaciohydraulic model
and these findings have implications for our understanding of ice-marginal lakes, moulins and subglacial lakes.

The design of flood control structures requires rainfall intensity estimation for design discharge computation. To make the rainfall intensity values easily available in Warri, Delta state of Nigeria, this research developed rainfall models. Rainfall intensity data were collected and analysed. The statistical method of least squares was used to fit the curves generated. Intensityduration models were developed and presented in graphical curves. Quotient method was adopted in the modeling. Another set of models developed are intensity-frequency models which gave correlation coefficient values of between 0.8694 and 0.9689 showing good fit. These models were used to produce rainfall intensity values for durations of 30, 60, 90 and 120 minutes and some return periods between 5 years and 30 years.

La presente copia viene fornita all'autore non per scopi commerciali, ma solo per scopi didattici o scientifici senza fini di lucro. Non deve essere riprodotta o distribuita dall'autore Provided for non-commercial research and education use. Not for reproduction, distribution or commercial use L'articolo è stato pubblicato sulla rivista Acque Sotterranee -Italian Journal of Groundwater edita dall'Associazione Acque Sotterranee. L'articolo può essere usato dall'autore per la didattica o per condividerlo con i colleghi. Non può essere riprodotto o inserito in siti web dell'autore o di terze parti nella forma pdf impaginata dalla Casa Editrice. Può altresì essere inserito in formato txt o Word nel sito dell'autore citando la rivista in cui è stato pubblicato e il DOI ad esso collegato This article appeared in Acque Sotterranee -Italian Journal of Groundwater published by Associazione Acque Sotterranee. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited.

This paper aims to quantify the potential impacts of the Grand Ethiopian Renaissance Dam (GERD) on the River Nile System within Sudan territories, in the context of hydrology. GERD reservoir with a capacity of (74 Km 3) is approximately 1.5 times the mean annual flow of the Blue Nile, which contributes by 57% of the River Nile runoff. According to Ethiopian proposal, the GERD is going to be filled to the full supply level of 640 m a.m.s.l in 6 to 7 years. The first filling of GERD reservoir was planned to be in 2014, but it is postponed until the writing of this report. However, it's most likely to be started this year 2020. Consequently, significant impacts are highly anticipated during this first filling period, and all over the long-term operation. Definitely, this will change the Blue and Main Nile hydrological regime. In order to achieve the research objectives, a daily time step Rule Based Simulation model has been developed using River Ware Software (University of Colorado) representing the entire River Nile system within Sudan. Three scenarios were adopted, baseline (Hydrological System without GERD), GERD first filling and long-term operation. River inflows, water levels, runoff and hydrograph shapes within Sudan water system were investigated and compared to the average baselines, taking into consideration the recent Dams' operation policies and rules. In addition, a simple-approach operation scenario was adopted for GERD. Likewise, as hydrological inputs, 30 years of historical time series were used. Given the above, the hydrological impacts in six representative River Nile reaches within Sudan were estimated, then highlighted and judiciously investigated. In summary, it could be concluded that, during the first filling of GERD, the runoff of the Blue Nile will decrease by 30%. While, for the Long Run, significant changes are expected for to the Blue Nile hydrograph, resulting in slight to moderate changes for the Main Nile Hydrograph. It's expected that the impacts of GERD on River Nile hydrology will lead to increasing average discharges during summer period by a range of 10-500% for different months and hydrology, on the other hand, reducing flood peak by approximately 10-25%. In the long run, Water Levels in different reaches are expected to vary by ± (2 to 3) meters. It's concluded that operation policies of the existing Sudanese dams will no longer be valid for the new Situation after GERD, further studies are highly recommended to be conducted.

Analyses of long-term data are an important component of climate-change research because they can help further our understanding of the effects of climate change and can help establish expectations for biological responses to future climate changes. We used macroinvertebrate data to assess whether biological trends associated with directional climate change could be detected in routine biomonitoring data from Maine, North Carolina, and Utah. We analyzed data from 8 long-term biomonitoring sites that had 9 to 22 y of data, and focused on thermal-preference metrics based on coldand warm-water-preference trait groups. The thermal-preference metrics were derived primarily from weighted-average or generalized-linear-model inferences based on data from each state database and are region specific. Long-term trends varied across sites and regions. At some sites, the thermal-preference metrics showed significant patterns that could be interpreted as being related to directional climate change, whereas at others, patterns were not as expected or were not evident. The strongest trends occurred at 2 Utah sites that had §14 y of data. At these sites, cold-water taxa were negatively correlated with air temperature, and, when years were grouped into hottest-and coldest-year samples, were strongly reduced in the hottest-year samples. Results suggest that thermal-preference metrics show promise for application in a biomonitoring context to differentiate climate-related responses from other stressors.

To enable a relevant interpretation of otolith strontium : calcium (Sr/Ca) variations in terms of habitat shifts of eels, the Sr/Ca-salinity relationship in eel otoliths was validated. Downstream and upstream migrations of young eels were reproduced in the laboratory by transferring groups of fish every 2 months between aquaria filled with water coming from the Dordogne river (salinity = 0), the upper Gironde estuary (salinity = 5), the lower Gironde estuary (salinity = 25) and the coast (salinity = 30), which represented the salinity gradient observed in the Gironde-Garonne-Dordogne watershed. Ontogenetic changes in otolith Sr/Ca were assessed in two groups of control fish that were kept in one of either two constant salinities (fresh water or seawater). X-ray electron microprobe (wavelength dispersive spectrometry, WDS) analyses of Sr/Ca ratios in the otoliths showed that the change of aquarium was recorded as a Sr/Ca increase (downstream migration) or a Sr/Ca decrease (upstream migration). No ontogenetic effect was detected in otoliths of control fish outside glass eel marks in either group of fish. The electron microprobe (WDS) analysis of the Sr/Ca life (transected in several otoliths of eels caught in the Gironde-Garonne-Dordogne watershed) showed that some of them were migrant eels that had experienced one major habitat shift during their continental life.

In order to manage the world's increasingly scarce water resources we must have a sound understanding of how water moves around the planet and what influences water quality. Fundamentals of Hydrology provides an engaging and comprehensive introduction to this subject and provides real-life examples of water resource management in a changing world.

Twenty-five rangeland sites were monitored over two decades first to assess the impact of the 1983-1984 droughts on fodder resources, then to better understand ecosystem functioning and dynamics. Sites are sampled along the south-north bioclimatic gradient in Gourma (Mali), within three main edaphic situations: sandy, loamy-clay and shallow soils. In addition, three levels of grazing pressure where systematically sampled within sandy soils. Located at the northern edge of the area reached by the West African monsoon, the Gourma gradient has recorded extremes in inter-annual variations of rainfall and resulting variations in vegetation growth. Following rainfall variability, inter-annual variability of herbaceous yield increases as climate gets dryer with latitudes at least on the sandy soils sites. Local redistribution of rainfall explains the high patchiness of herbaceous vegetation, especially on shallow soils. Yet spatial heterogeneity of the vegetation does not buffer between year yield variability that increases with spatial heterogeneity. At short term, livestock grazing during the wet season affects plant growth and thus yield in direction and proportions that vary with the timing and intensity of grazing. In the longer term, grazing also impinges upon species composition in many ways. Hence, long histories of heavy grazing promote either long cycle annuals refused by livestock or else short cycle good quality feed species. Primary production is maintained or even increased in the case of refusal such as Sida cordifolia, and is lessened in the case of short cycle species such as Zornia glochidiata. These behaviours explain that the yield anomalies calculated for the rangelands on sandy soils relative to the yield of site less grazed under similar climate tend to be negative in northern Sahel where the scenario of short cycle species dominates, while yield anomalies are close to nil in centre Sahel and slightly positive in South Sahel where the refusal scenario is more frequent. Because grazing promotes short cycle species, grazed rangelands respond faster to droughts.

Land surface schemes are vital components of general circulation models (GCMs) which provide the fluxes of heat, water and momentum at the land-atmosphere interface. The fluxes simulated by these schemes are especially dependent on the way in which the canopy (or 'bulk stomatal') conductance for plant transpiration is modelled. Considerable research has been carried out into the dependences of canopy conductance on the local environment, and empirical relationships for such dependences have been obtained by fitting the data collected in field and laboratory experiments. However, observed leaf level relationships between stomatal conductance and net photosynthesis suggest an alternative approach. Given an appropriate algorithm for scaling these values up to canopy level, such relationships allow canopy conductance values to be derived from (comparatively) well validated models of leaf photosynthesis. This approach is likely to become especially attractive as land surface schemes are extended to simulate CO 2 fluxes, since the shared environmental dependences of canopy conductance and photosynthesis reduce the number of model parameters which require independent specification. This paper is concerned with the evaluation of canopy level relationships between photosynthesis and conductance using data from the first international satellite land surface climatology project (Islscp) field experiment (Fife). Simultaneous measurements of CO 2 and water vapour fluxes, taken over a predominantly C 4 grassland, are used to independently test the conductance and photosynthesis models. Based on these tests, a simple coupled model of canopy conductance and photosynthesis is developed, which produces a good match to the experimental data.

Stretta è la relazione che corre tra lo svolgimento millenario della tecnica di lavoro dell'uomo, e i rapporti con l'ambiente naturale. L'uomo primitivo, come l'animale, raccoglie e consuma frutti spontanei colla semplice operazione prensile, e come l'animale fugge senza controllo davanti al dirompere del fenomeno naturale che ne minacci la vita. Come la produzione artificiale di prodotti pel consumo, e l'accumulazione di riserve di prodotti stessi e di utensili, lo costringe a fissarsi, così lo costringe a difendersi dalle minacce di meteore e sconvolgimento naturali. Una tale difesa, non diversamente da quella contro altri gruppi concorrenti alla sede migliore, o predatori della accumulata riserva, non può che essere collettiva. Da queste esigenze collettive, come tante volte vedemmo, nasce la divisione in classi e lo sfruttamento da parte dei dominatori.

In Marx, "il modo di produzione capitalistico presuppone il dominio dell'uomo sulla natura". Esso presuppone anche la guerra della natura contro l'uomo. Una troppo generosa e prodiga natura non sarebbe ambiente favorevole al sorgere del capitalismo.

Unsaturated infiltration into the Ramiha silt loam, an Andic Dystrochrept, follows the classic pattern. A rapid drop-off from a high flow rate, seemingly induced by capillary attraction, appears followed by an apparent steady-flow maintained by gravity at around 0.5 mm s Ϫ1 . Beyond 100 min, however, the infiltration rate climbs nearly linearly to exceed 4 mm s Ϫ1 as the soil's water repellency breaks down. This is only evident after a period that might exceed the observer's attention span. The hydrophobicity in this case could be due to one, or a combination, of the many unusual characteristics of this soil-its low bulk density (0.8 Mg m Ϫ3 ), its strongly aggregated nature, the presence of mycorrhizal fungi, its high organic matter content (16.5%), or the presence of allophanic clay (4%).

Floods are one of the most frequently occurring natural disasters in Indonesia. It is therefore of special concern to reduce the risk of flood fatalities and other damage. The purpose of this study is to design a flood early warning system based on the Internet of Things (IoT). In this work, we use an ultrasonic HC-SR04 sensor to collect information about water levels. Further, we use an MCU8266 node as a microcontroller to analyze the sensor data and test it using a fuzzy inference system (FIS). To monitor the server activities, a Blink application is used as an iCloud IoT to hook up to smartphone devices. The test results show that all the devices function properly and that the system can classify water levels into normal, standby, alert, and danger categories in real time. Thus, the server can send information to the output device before a flood disaster occurs.

The management and maintenance of groundwater quality play a vital role in the development of a region as well as health aspects of living beings in that area. The contamination of groundwater also affects crop yield and production of crop. Hence a systematic study has been carried out to assess the ground water quality in Vallabharaopalem (Latitude: 16.0558 0 N; Longitude: 80.5251 0 E) and Upparapalem (Latitude: 16.0804 0 N; Longitude: 80.5013 0 E) villages of Ponnur mandal in Guntur district, which is a part of western delta of Krishna river in Andhra Pradesh state of India. The formations in the study area belong to recent alluvium. Groundwater occurs under unconfined conditions. The groundwater is analyzed for various physico-chemical parameters. Values of most of these parameters such as electrical conductivity fall beyond the standard limits for drinking water. The chloride-bicarbonate ratio more than 6 as per Revel's classification suggested that the groundwater is injuriously contaminated with saline water. The present attempt is made to understand the contamination in the groundwater quality. Suitable precautionary measures are suggested for sustainable development of ground water quality to maintain the environmental balance in the study area. The present study can be extended in similar critical contaminated areas throughout the world.

A 2-D mathematical model (SED-2) was developed simulating the sediment transport in alluvial shallow-wide streams in order to solve practical problems in the Nile River. The Finite Difference technique was used to solve the convectiondiffusion equation of the suspended sediment in open channels. A 2-D hydrodynamic model (HYD-2) was used to describe the flow field solving the Reynolds form of the Navier-Stokes momentum equations in two dimensions in addition to the continuity equation. The developed 2-D mathematical model was verified using actually measured field data. The field data were collected from one of the main canals of irrigation network in Egypt called El-Naser main canal. Good agreement was observed between the model results and the field observations. The model could be applied for solving local hydraulic and navigation problems where some reaches of the Nile River suffering. Various proposals could be investigated and the optimal solution in each case could be reached.

Complementary analysis of satellite mission data (altimetry, Moderate Resolution Imaging Spectroradiometers (MODIS)) and climate fields over 2000–2009 was conducted to investigate the variability of the water cover surfaces and the geographical source of water inflowing into the Lake Poopó system. The results suggest that over the time span of 2000–2009 a great part of the variability of the Poopó system originates from geographic sources other than Lake Titicaca. Possible alternative causes include climate change inducing increased temperatures and greater evaporation rates along the Altiplano; increased glacier and snow melting over the Andes Cordillera; and a potential increased anthropogenic water use (such as irrigation, minery, etc.) throughout the path of the Desaguadero River (which connects lakes Titicaca and Poopó). This change in the hydrology of this region could lead to a collapse of water supplies and endanger the already fragile Poopó system as well as the regional socioeconomic system, which closely depends upon it.

Floodplains mitigate against extreme annual hydrologic phenomena by storing substantial volumes of water which would otherwise increase flood volumes. Later floodplains gradually release this water which serves to maintain baseflows. This phenomenon, called bank storage, has important physical and ecological ramifications which in addition to reducing flood peaks, include sustaining riparian vegetation and improving water quality. We developed a model of bank storage based upon the earlier work of Neuman and Witherspoon (Wat. Resour. Res., 6 (1990) 889, 1376; 7 (1971) 611). This model (WaTab2D) treats the flow of water through floodplain soils for a general twodimensional case: non-symmetrical valleys, non-symmetrical channel banks, non-uniform hydraulic geometry and non-zero boundary fluxes. The total volume that can potentially be released from bank storage is nearly proportional to the width of the floodplain, the height of the bank, and the specific yield; the duration over which water is released from bank storage increases with increasing floodplain width and decreases with hydraulic conductivity. Drainage of water from the floodplain with a drop in channel water level occurs over a period of days in gravel, weeks to a few years in sand, years in silt, and decades in clay. The rate of drainage decreases in an exponential-like manner. ᭧ 1997 Elsevier Science B.V.

Modeling surface water quality using soft computing techniques is essential for the effective management of scarce water resources and environmental protection. The development of accurate predictive models with significant input parameters and inconsistent datasets is still a challenge. Therefore, further research is needed to improve the performance of the predictive models. This study presents a methodology for dataset pre-processing and input optimization for reducing the modeling complexity. The objective of this study was achieved by employing a two-sided detection approach for outlier removal and an exhaustive search method for selecting essential modeling inputs. Thereafter, the adaptive neuro-fuzzy inference system (ANFIS) was applied for modeling electrical conductivity (EC) and total dissolved solids (TDS) in the upper Indus River. A larger dataset of a 30-year historical period, measured monthly, was utilized in the modeling process. The prediction capacity of the develo...

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of ...

The transient response to projected climate change of two ice caps in the central Icelandic highland was simulated with a vertically integrated ice-flow model coupled to a degree-day mass-balance model. The ice caps, Langjökull and Hofsjökull, are of similar size (area ∼900 km2 and volume ∼200 km3) and located only ∼30 km apart. The climate change simulations were started in 1990 from steady states corresponding to the average climate of 1981–2000 and driven with observed weather parameters until 2005. Thereafter, the forcing was according to a Nordic climate change scenario based on the IPCC B2 emission scenario. The simulations during the period 1990–2005 compare reasonably well with observations of mass-balance and glacier extent. Both ice caps are projected to essentially disappear during the next 100 to 200 years. Langjökull, which disappears within the next 150 years, shows larger mass-balance sensitivity to warming than the higher elevated Hofsjökull, where ice on the highest...

This study compared the centrifuge and pressure plate methods with appropriate run durations. Samples collected in tropical soils located in Brazil along a 10-km local hydrosequence across the Cerrado-Amazonia transition (Set 1) and along a 350-km regional toposequence across the Cerrado region (Set 2) were selected to compare and discuss statistically the similarity of the soil water retention recorded by using the pressure plate and centrifuge methods. The results showed good agreement (R 2 = 0.99) for the 1:1 comparison of measured pointwise soil water content values (Set 1) as well as for the fitted soil water content curves by the van Genuchten model using data points obtained with the two methods (Set 2). Thus, the centrifuge method should be considered as an appropriate method for determining soil water retention properties not only because of similar results with the pressure plate method but also because it is much less time consuming.

The hydraulic performance of round-cornered rectangular labyrinth weirs with varying weir heights and effective lengths has not been explored in the existing literature to the authors’ knowledge. The purpose of this experimental study was to see how the height and effective length of round-cornered rectangular labyrinth weirs affect their discharge efficiency. Nine flat-crested rectangular labyrinth weirs made of high-density polyethylene (HDPE) were tested in a rectangular flume under various discharges to fulfill the goals of this study. The discharge coefficients for the weirs were then calculated. The hydraulic efficiency of weirs with round corners increases as the weir height (P) increases, according to the findings; however, with effective length of the weir to channel width ratios (LC/B) ≤ 1.78, the effect of the weir height diminishes. For the HT/P ranges used in this study, 0.1 ≤ HT/P ≤ 0.65, the round-cornered rectangular labyrinth weirs with higher LC/B ratios (greater M...

A new graphical technique is developed that takes advantage of time-subsidence data collected from either traditional extensometer installations or from newer technologies such as fixed-station global positioning systems or interferometric synthetic aperture radar imagery, to accurately estimate storage properties of the aquifer and vertical hydraulic conductivity of semi-confining units. Semi-log plots of time-compaction data are highly diagnostic with the straight-line portion of the plot reflecting the specific storage of the semi-confining unit. Calculation of compaction during one-log cycle of time from these plots can be used in a simple analytical expression based on the Cooper-Jacob technique to accurately calculate specific storage of the semi-confining units. In addition, these semi-log plots can be used to identify when the pressure transient has migrated through the confining layer into the unpumped aquifer, precluding the need for additional piezometers within the unpumped aquifer or within the semi-confining units as is necessary in the Neuman and Witherspoon method. Numerical simulations are used to evaluate the accuracy of the new technique. The technique was applied to time-drawdown and time-compaction data collected near Franklin Virginia, within the Potomac aquifers of the Coastal Plain, and shows that the method can be easily applied to estimate the inelastic skeletal specific storage of this aquifer system.

This study explored the occurrence and distribution of ordinary high water mark (OHWM) indicators in non-perennial streams in the Western Mountains, Valleys, and Coast (WMVC) Region of the United States. Physical and biological indicators of the OHWM were recorded and ranked (weak, moderate, or strong) at 150 ephemeral or intermittent stream sites sampled across the region. Three primary OHWM indicators-topographic break in slope, change in sediment characteristics, and change in vegetation characteristics-were found to be ubiquitous throughout the WMVC Region. At each stream sampled, a combination of at least two of these primary indicators was found to express a signature on the landscape, generally consistent with the lateral boundaries of the active channel. The distribution of the primary indicators and their rankings within the region showed no relationships to various climate, watershed, or channel characteristics examined using multivariate statistical analysis. This suggests the robust nature of these primary indicators and the active channel signature for delineating the OHWM in non-perennial streams throughout the WMVC Region. These findings support a more informed and consistent approach to OHWM delineation in the WMVC Region.

Knowledge on the spatial variability and temporal trends of mean rainfall is essential for efficient management of water resource and agriculture. We have analyzed the rainfall data of the Cauvery river basin, a larger river basin in Southern India which plays a significant role in agricultural development and consequently in the overall growth of Karnataka, Tamil Nadu, Pondicherry and some parts of Kerala. The analysis includes distribution, variability and trends in rainfall over the Cauvery basin during twentieth century . The impact of climate change on temporal and spatial patterns of rainfall over smaller spatial scales is clearly noticed in this analysis. It is also observed that the coefficient of variation shows significant fluctuations during the winter than other seasons. Long term changes in rainfall have been determined by. Significant decreasing trend in the winter rainfall and increasing trend in the post-monsoon season with insignificant levels have been inferred based on the Mann-Kendall rank statistics and linear trend. Overall, insignificant decrease in annual rainfall over the Cauvery river basin has observed during twentieth century.

We have developed NEMO-VN1 (NanoElectronic MOdelling), a new modelling tool that simulates a wide variety of quantum devices including Quantum Dot (QD), Resonant Tunneling Diode (RTD), Resonant Tunneling Transistor (RTT), Single Electron Transistor (SET), Molecular FET (MFET), Carbon Nanotube FET (CNTFET), Spin FET (SPINFET).

An accurate representation of reality in numerical variably-saturated flow models requires reliable estimates of necessary model parameters. Inverse modeling seeks to estimate parameters such as the saturated and residual water contents, the saturated hydraulic conductivity, the shape parameters of the soil hydraulic functions, using easily attainable observations of actual or cumulative water fluxes, pressure heads, water contents, and concentrations. The inverse procedure usually combines the nonlinear leastsquares-based (SSQ) parameter optimization method with a numerical solution of the variably-saturated flow and transport equations. The SSQ-based inverse method is however sensitive to outliers. A novel Squared ε-Insensitive Loss Function (SILF) approach is introduced in this study. The SILF approach is inspired by the ε-insensitive loss function proposed by Vapnik (1995). The objective function used in the SILF approach is similar to the least-squares objective function, except that it penalizes only for errors greater than a certain predefined acceptable error term ε. The SILF approach shows an improved performance over the SSQ approach in estimating the soil hydraulic parameters. Apart from providing robust estimates of the soil hydraulic parameters, the SILF approach also gives an approximation of the relative measurement error during sampling.

In this paper, an experimental investigation was conducted to study the effect of flow and transition parameters on the protection length downstream (DS) of the sudden expansion. A laboratory flume of 10 cm wide, 31 cm deep and 3 m long was used to carry out the experimental work. Models of different contraction ratios ranged between 50% to 90% passage waterways were used during the experimental programs. Five positive slopes were used for each contraction. Vertical transition in the bed were also changed for a particular bottom slope and a specified lateral contraction ratio. Different discharges were used for each bed slope. The dimensional analysis was used to correlate the relative protection length to the other relevant parameters. The effect of all these parameters on the relative protection length DS of sudden expansion were analyzed and discussed. It has been found that the relative protection length is function of the contraction ratio, the relative height of vertical transition, the channel bottom slope and the incoming Froude number. The relative protection increases with the increase of the incoming Froude number, and increases with the increase of the relative height of the vertical transition length, while it decreases with the increase of the contraction ratio. The steep slope has a major effect on the relative protection length, the trend of increases decreases as the slope decreases till a minimum effect when the bed is horizontal (limiting value of the positive slope).

Relationships were determined between methane (CH 4 ) production and in situ conditions J. L. Wadham* within the permafrost active layer during a single melt season at Stordalen, Sweden, with E. R. C. Hornibrook † and a specific emphasis on temperature sensitivity of methanogenesis. In situ temperature, R. D. Pancost ‡ moisture, pH, dissolved organic carbon, and CH 4 concentration data were measured at three contrasting active layer sites (sedge mire, Sphagnum mire, and ombrotrophic bog),

An expression for the distribution function of peak runoff is derived, combining results of frequency analysis of rainfall volumes with the traditional concepts of runoff coefficients and the unit hydrograph. Rainfall volume, scaled with respect to its duration, is assumed to follow a gamma distribution, whereas for the runoff coefficient a beta distribution is applied. Hydrograph characteristics are considered to be deterministic variables. A closed form analytical expression is achieved when some minor simplifications are made. The approach is tested and validated against data from 17 small Swiss drainage basins, for which unit hydrographs have been determined. The runoff response of these basins is very different in relation to both the distribution of the runoff coefficient and hydrograph characteristics, which is also reflected in the behaviour of the distribution of peak flow. Four main response classes of basins are identified that can be related to the physiography of the basins. ᭧ 1998 Elsevier Science B.V. All rights reserved.

Physically-based groundwater models (PBMs), such as MODFLOW, contain numerous parameters which are usually estimated using statistically-based methods, which assume that the underlying error is white noise. However, because of the practical difficulties of representing all the natural subsurface complexity, numerical simulations are often prone to large uncertainties that can result in both random and systematic model error. The systematic errors can be attributed to conceptual, parameter, and measurement uncertainty, and most often it can be difficult to determine their physical cause. In this paper, we have developed a framework to handle systematic error in physically-based groundwater flow model applications that uses error-correcting data-driven models (DDMs) in a complementary fashion. The data-driven models are separately developed to predict the MODFLOW head prediction errors, which were subsequently used to update the head predictions at existing and proposed observation wells. The framework is evaluated using a hypothetical case study developed based on a phytoremediation site at the Argonne National Laboratory. This case study includes structural, parameter, and measurement uncertainties. In terms of bias and prediction uncertainty range, the complementary modeling framework has shown substantial improvements (up to 64% reduction in RMSE and prediction error ranges) over the original MOD-FLOW model, in both the calibration and the verification periods. Moreover, the spatial and temporal correlations of the prediction errors are significantly reduced, thus resulting in reduced local biases and structures in the model prediction errors.

The Hindukush Karakoram Himalayan mountains contain some of the largest glaciers of the world, and supply melt water from perennial snow and glaciers to the Upper Indus Basin (UIB) upstream of Tarbela dam, which constitutes greater than 80% of the annual flows, and caters to the needs of millions of people in the Indus Basin. It is therefore important to study the response of perennial snow and glaciers in the UIB under changing climatic conditions, using improved hydrological modeling, glacier mass balance, and observations of glacier responses. However, the available glacier inventories and datasets only provide total perennial-snow and glacier cover areas, despite the fact that snow, clean ice and debris covered ice have different melt rates and densities. This distinction is vital for improved hydrological modeling and mass balance studies. This study, therefore, presents a separated perennial snow and glacier inventory (perennial snow-cover on steep slopes, perennial snow-cover...

Increased productivity from sewage effluents can enhance species richness locally. Results from a study of spottail shiners (Notropis hudsonius) in 1999 showed that prevalence and the mean number of myxozoan parasite species per host were higher downstream of the wastewater outflow from the Island of Montreal than upstream in the St. Lawrence River, Quebec, Canada. This was attributed to organic enrichment of the sediments which presumably lead to increased densities of oligochaetes, the alternate hosts, downstream of Montreal. Spottail shiners subsequently were collected every August/early September in 2001-2004 to examine the stability and repeatability of these patterns. Prevalence and mean number of myxozoan species per fish typically were again higher downstream of the sewage source each year compared to upstream, although there was no significant difference in these measurements pooled across years between localities immediately upstream and downstream of the effluent outflow. Density of the oligochaete Limnodrilus hoffmeistereri, a common alternate host of myxozoans, was much higher at two downstream localities than at an upstream one. At a larger spatial scale, mean myxozoan infracommunity richness across sites in the St. Lawrence River was negatively correlated with mean water levels measured in the 3 months prior to fish sampling. Results suggest that on a local scale, variations in prevalence and diversity among localities are influenced by municipal effluents, but that at a landscape scale annual variations across sites are affected by the hydrological regime and climate. In effect, water level fluctuation had a landscape-wide impact that was superimposed over pollution-induced local variations.

Urban flooding is an inevitable problem for many cities around the world. In the present paper, modelling approaches and principles for analyses of urban flooding are outlined. The paper shows how urban flooding can be simulated by one-dimensional hydrodynamic ...

Aquatic coastal systems are affected by high fluctuations in salinity and the zooplankton may rely on dispersal or dormancy to recolonise these environments. Here, we analysed the long-term dynamics of the zooplankton community over 6 years during large salinity fluctuations in a coastal lagoon (Garças Lagoon, Brazil) and the effect of salinity on the hatching patterns of the resting egg bank. We hypothesised that salinity is the main driving factor of the zooplankton community structure, and that increases in salinity reduce the species richness and the abundance of hatchlings. Multiple regression analysis showed that salinity was associated negatively with species richness in the open water, whereas total phosphorus and chlorophyll-a concentrations were negatively and positively related to abundance respectively. Redundancy analysis demonstrated that temporally structured environmental variables (total phosphorus and salinity) were important for zooplankton composition. Periods of...

Afghanistan is highly prone to intense and recurring natural hazards, including earthquakes, floods, flash floods, landslides, avalanches, and droughts. Where 54% of the natural disasters in Afghanistan are water-related and makes the country the second most vulnerable country to floods worldwide. The country is prone to river flooding which cause substantial destruction to crops, human lives, and properties. Helmand River Basin is the largest of the five river basins in Afghanistan. It is a closed basin, which covers the southern half of the country draining to the unique Sistan depression near the Afghan- Iranian Border. About 80% of the population of the basin depends on agriculture and livestock for their livelihood. The middle and lower parts of the basin supports extensive agriculture. Although floods affect almost every part of the basin with varying intensity and frequency, the middle and lower parts of the basin is regarded as one of the most flood vulnerable areas. Unfortunately, residents in the flood prone area are, meanwhile, not sufficiently aware of flooding consequences due to the inadequate information and lack of quality flood data. Thus, the flood prone area has been carelessly developed for settlement and cultivation purposes.
Floods in Afghanistan Rivers are due to convective rainfall or snowmelt and sometimes coupled. Helmand River likewise experiences flood due to intense rainfall and rainfall coupled with rapid snowmelt. Where the intense rainfall-induced floods occur mainly in spring, which lies under the flash flood category. Such flash floods strike the flood prone area for a short duration, whereas the rain and snow-fed coupled floods last for a longer period.

Numerical programs for simulating flow and reactive transport in porous media is essential for predicting reservoir properties related to CO 2 sequestration performance, subsurface storage and risk assessment. In this paper we solve the Navier Stokes' equation using finite difference method, on a simulated porous rock structure, to study the velocity distribution of fluid flowing through it under a constant pressure gradient. A reactive solute carried through the fluid is allowed to interact with the minerals in the rock. This chemical reaction dissolves the mineral which changes the rock structure thus affecting its flow properties. These changes of flow properties are studied with variation in reactive solute concentration and pressure field. The different mechanisms of dissolution responsible for the variation of flow properties for the different parameters is predicted. Before the onset of homogeneous dissolution, variation in porosity follows a power-law behaviour with change in permeability when the latter is scaled by the concentration of the reactive species. The simulation results are compared with available experimental data and found to give a reasonable match.

Hydrology is the single most important abiotic factor in the formation and functioning of a wetland. Many limitations still exist to accurately characterizing wetland hydrology over large spatial extents, especially in forested wetlands. Imaging radar has emerged as a viable tool for wetland flood mapping, although the limitations of radar data remain uncertain. The influence of incidence angle on the ability to detect flooding in different forest types was examined using C-HH Radarsat-1 data (23.5°, 27.5°, 33.5°, 39.0°, 43.5°, and 47.0°) during the leaf-off and leaf-on seasons. The ability to detect flooding under leaf-on conditions varied much more according to incidence angle while forest type (open canopy tupelo-cypress, tupelo-cypress, and bottomland hardwood) had a greater effect during the leaf-off season. When all forest types were considered together, backscatter generally decreased with increasing incidence angle under all conditions (2.45 dB between 23.5°and 47.0°flooded, leaf-off; 2.28 dB between 23.5°and 47.0°not flooded, leaf-off; 0.62 between 23.5°and 43.5°flooded, leaf-on; 1.73 dB between 23.5°and 43.5°not flooded, leaf-on; slope was not constant between incidence angles), but the distinction between flooded and non-flooded areas did not decline sharply with incidence angle. Differentiation of flooded and non-flooded forests was similar during the leafoff and leaf-on seasons. The ability to detect inundation under forest canopies was less than expected at smaller incidence angles and greater than expected at larger incidence angles, based on the results of previous studies. Use of a wider range of incidence angles during the entire year increases the temporal resolution of imagery which may, in turn, enhance mapping of inundation beneath forest canopies.

Cross-borehole geoelectrical imaging, in particular electrical resistivity tomography (ERT) and transmission radar tomography, can provide high-resolution images of hydrogeological structures and, in some cases, detailed assessment of dynamic processes in the subsurface environment. Through appropriate petrophysical relationships, these tools offer data suitable for parameterising and constraining models of groundwater flow. This is demonstrated using cross-borehole radar and resistivity measurements collected during a controlled vadose zone tracer test, performed at a field site in the UK Sherwood Sandstone. Both methods show clearly the vertical migration of the tracer over a 200 h monitoring period. By comparing first and second spatial moments of changes in moisture content predicted from a numerical simulation of vadose zone flow with equivalent statistics from two-and three-dimensional ERT and cross-borehole radar profiles the effective hydraulic conductivity is estimated to be approximately 0.4 m/d. Such a value is comparable to field estimates from borehole hydraulic tests carried out in the saturated zone at the field site and provides valuable information that may be utilised to parameterise pollutant transport models of the site. q

Recently available hydrological data from Hukou station at the junction of the Poyang Lake with the Yangtze River along with other data from stations in the Poyang Lake basin have allowed further examination and understanding of the basin effect (basin discharge generated by rainfall) and the Yangtze River blocking effect on variations of the Poyang Lake level and floods at annual to decadal scales. Major results show that the basin effect has played a primary role influencing the level of Poyang Lake and development of severe floods, while the Yangtze River played a complementary role of blocking outflows from the lake. In most cases, only when the basin effect weakened did the river effect become large, a relationship indicating that the river's blocking effect diminishes when the lake level is high from receiving large amount of basin discharge, albeit a few exceptions to this relationship occurred when river flow also was elevated from receiving large rainfall discharges in upstream areas. Moreover, the basin effect has become stronger in the period 1960-2003 in accordance with the increase of warm season rainfall in the Poyang Lake basin. In particular, large increases of the basin's rainfall in the 1990s corresponded to the most severe floods (in 1998, 1995, and 1992) of the last 4 decades. The strong increase of warm season rainfall in the Poyang Lake basin in the 1990s is consistent with the recent southward shift of major warm season rain bands in eastern China. Results of this study provide a utility for improving predictions of the Poyang Lake level and floods, which affect a population of about 10 million. ª