APPLICATION OF A GROUPED RESPONSE UNIT HYDROLOGICAL MODEL TO A NORTHERN WETLAND REGION

Applications of hydrological models to northern wetland-dominated regions have been limited in the past to a few case studies on small basins employing ‘lumped’ models. Only recently have there been attempts to apply the grouped response unit (GRU) distributed modelling approach using terrain classifications to these same basins. This study summarizes recent efforts in applying such a model. For the purposes of implementing the GRU approach, terrain types that are hydrologically significant and characteristic to the wetland-dominated regime were successfully discriminated using a principal component analysis and a hybrid unsupervised/supervised classification technique on Landsat–Thematic Mapper imagery. The terrain classifications were then used as input into a distributed hydrological model for calibration and validation using recorded spring runoff events. Preliminary model applications and results are described. Calibration to a historic spring runoff event yielded an r² value of 0.86. Model validation, however, yielded much poorer results. The problems of model applicability to this region and limitations of sparse data networks are highlighted. The need for more field research in this type of hydrological regime, and associated improvements to the model parameter set are also identified.     

USE OF TRITIUM IN HYDROLOGY

SUMMARY

The Coastal Plain aquifer of Israel, of Plio-Pleistocene Age, stretches from Binyamina in the North to the Gaza Strip in the South-a distance of about 112 km and has an average width of about 15 Km. The allowed withdrawal is estimated at about 200 MCM/year.

As a result of an average yearly withdrawal of 426 MCM/year during the last 10 years the water levels dropped to a dangerously low position (-2)-(-4) m below sea level at distances of 3–5 Km from the coast, causing sea water intrusion which, in Tel Aviv and Emek Hefer, endangered water supply wells.

As a counter-measure, artificial groundwater recharge through wells was practiced in Emek Hefer since 1959. Recharge was practiced in 7 wells at a rate of 6 MCM/year, the water coming from adjacent Cretaceous limestone aquifers.

In Tel Aviv a fresh water barrier was established in 1964 by injecting Lake Kinereth water into 17 wells during winter at a rate of 6 MCM/winter. In the rest of the Coastal Plain water was injected to the aquifer through about 40–45 wells at a total yearly rate of about 10–12 MCM.

Recharge by spreading is practiced in Yavneh at a rate of about 10–13 MCM per winter, also recharge by spreading is practiced with flood water of Nahal Shikma at a rate of up to 8 MCM/winter.     

APPLICATION OF THE MULTIGRID METHOD IN NUMERICAL SIMULATION OF SEDIMENT TRANSPORT

IINTRODUCTIONThemultigridmethod(Brandt,1988)iswidelyusedinmanydisciplinesandengineeringsubjects,especiallyintheareaofComputationalFluidMechanicsbecauseofitshighefficiencyincomputation.Themultigridmethodhasbeenprovenintheorytobeoneofbestnumericalmethodsforsolvinglinearellipticproblemsbecausetheloadofcomplltationisindirectproportiontothenumberofgridnodes;theconvergentspeedofmultigridmethodisirrelevanttothesizeofgird.Soitissuitableforthenumericalsimulationoffullscaleengineeringprojects.The…     

DEVELOPMENT OF A SURFACE PLUME MODEL AND ITS APPLICATION TO SEDIMENT TRANSPORT MODELLING OF DREDGING IN COASTAL WATERS

I INTRODUCTIONSediment dredging operations are effective means of maintaining the natural navigation channel ofshipping for transportation of passengers and cargoes (Goldbeck 1998, Wakeman 1998). Expansions ofexisting ports to facilitate the groWth in marine traffic often necessitate navigation channel dredgingactivities (Foxworthy et. al. 1995, Luger et. al. 1998). Dredging is also heavily used for marine mining ofthe scabed deposits for gold or minerals (Anon 1996, Gamett 1996), and …     

NUMERICAL SIMULATION OF SEDIMENT TRANSPORT IN DYNAMIC FLOW CONDITIONS

1 INTRODUCTION Rivers as a source of life can at the same time impose devastating conditions on the environment. It is , therefore, imperative to analyse and predict river behaviour for different given conditions and engineering activities. Therefore, the use of simulation tools in this field has become a necessity. Many computational tools for simulation of sediment transport in rivers are now available that can be used for prediction and design under different flow conditions. However, …     

FLOOD MODELLING WITH GIS-DERIVED DISTRIBUTED UNIT HYDROGRAPHS

The concept of a spatially distributed unit hydrograph is based on the fact that the unit hydrograph can be derived from the time–area curve of a watershed by the S-curve method. The time–area diagram is a graph of cumulative drainage area contributing to discharge at the watershed outlet within a specified time of travel. Accurate determination of the time–area diagram is made possible by using a GIS. The GIS is used to describe the connectivity of the links in the watershed flow network and to calculate distances and travel times to the watershed outlet for various points within the watershed. Overland flow travel times are calculated by the kinematic wave equation for time to equilibrium; channel flow times are based on the Manning and continuity equations. To account for channel storage, travel times for channel reaches are increased by a percentage depending on the channel reach length and geometry. With GIS capability for rainfall mapping, the assumption of a uniform spatial rainfall distribution is no longer necessary; hence the term, spatially distributed unit hydrograph. An example of the application for the Waiparous Creek in the Alberta Foothills is given. IDRISI is used to develop a simple digital elevation model of the 229 km² watershed, using 1 km × 1 km grid cells. A grid of flow directions is developed and used to create an equivalent channel network. Excess rainfall for each 1 km × 1 km cell is individually computed by the Soil Conservation Service (SCS) runoff curve method and routed through the equivalent channel network to obtain the time–area curve. The derived unit hydrograph gave excellent results in simulating an observed flood hydrograph. The distributed unit hydrograph is no longer a lumped model, since it accounts for internal distribution of rainfall and runoff. It is derived for a watershed without the need for observed rainfall and discharge data, because it is essentially a geomorphoclimatic approach. As such, it allows the derivation of watershed responses (hydrographs) to inputs of various magnitudes, thus eliminating the assumption of proportionality of input and output if needed. The superposition of outputs is retained in simulating flood hydrographs by convolution, since it has been shown that some non-linear systems satisfy the principle of superposition. The distributed unit hydrograph appears to be a very promising rainfall runoff model based on GIS technology.     

Comparative analysis of a geomorphology‐based instantaneous unit hydrograph in small mountainous watersheds

A conceptual insytnataneous unit hydrograph (IUH) based on geomorphologival association of linear reservoirs (GR) previously developed by the authors has been compared with other IUH models: a distributed GR variation (GR(v)), the Nash IUH, the Chutha and Dooge IUH, and the Troutman and Karlinger IUH for the analysis of direct runoff hydrographs recorded in three experimental watershed of the north of Spain. The comparison was made through a calibration‐validation process in which a leave‐one‐out cross‐validation method was applied. The results indicate the satisfactory performance of all the models, with the advantage for the GR model of the dependence on only one parameter, which can be identified from the watershed and event characteristics. This property makes its use easier than that of other models. Copyright © 2011 John Wiley & Sons, Ltd.     

APPLICATION OF THE TRRL FLOOD ESTIMATION MODEL IN HYDROLOGICAL FORECASTING FOR CATCHMENTS WITH LIMITED DATA A CASE STUDY

１ＩＮＴＲＯＤＵＣＴＩＯＮＯｎｔｈｅｍｏｒｎｉｎｇｏｆ３０ｔｈＪａｎｕａｒｙ１９９２,ａＮａｉｒｏｂｉｂｏｕｎｄｐａｓｅｎｇｅｒｔｒａｉｎｆｒｏｍＭｏｍｂａｓａｏｎｔｈｅｍａｉｎｌｉｎｅｄｅｒａｉｌｅｄｉｎｔｏａｎｅｍｂａｎｋｍｅｎｔｔｈａｔｈａｄｂ...     

ON THE NUMBER OF FRACTIONS TO COMPUTE TRANSPORT OF SEDIMENT MIXTURES

1 INTRODUCTIONMany hydro-momhological mathematical models neglect the innuence of river bed maerialheterogeneity and its time and space changes during transport and related erosion/dePosition processes. Inthese models a rePresentative diameter of the river bed grain-size distribution (for examPle d5o) isspecified as initial data in each comPutational point of the modeled domain. Different d5o can be assignedto each ghd point but temPoral changes in bed material gradation cannot be simula…     

MODELLING THE IMPACT OF LAND USE CHANGE ON WATER QUALITY IN AGRICULTURAL CATCHMENTS

Export coefficient modelling was used to model the impact of agriculture on nitrogen and phosphorus loading on the surface waters of two contrasting agricultural catchments. The model was originally developed for the Windrush catchment where the highly reactive Jurassic limestone aquifer underlying the catchment is well connected to the surface drainage network, allowing the system to be modelled using uniform export coefficients for each nutrient source in the catchment, regardless of proximity to the surface drainage network. In the Slapton catchment, the hydrological pathways are dominated by surface and lateral shallow subsurface flow, requiring modification of the export coefficient model to incorporate a distance–decay component in the export coefficients. The modified model was calibrated against observed total nitrogen and total phosphorus loads delivered to Slapton Ley from inflowing streams in its catchment. Sensitivity analysis was conducted to isolate the key controls on nutrient export in the modified model. The model was validated against long-term records of water quality, and was found to be accurate in its predictions and sensitive to both temporal and spatial changes in agricultural practice in the catchment. The model was then used to forecast the potential reduction in nutrient loading on Slapton Ley associated with a range of catchment management strategies. The best practicable environmental option (BPEO) was found to be spatial redistribution of high nutrient export risk sources to areas of the catchment with the greatest intrinsic nutrient retention capacity. © 1997 by John Wiley & Sons, Ltd.     

STREAM-SUBSURFACE EXCHANGE, SUSPENDED SEDIMENT TRANSPORT, AND THE COUPLED TRANSPORT OF COLLOIDS AND CONTAMINANTS IN SEDIMENT BEDS

1 INTRODUCTION Alluvial streams generally have permeable bed sediments that can admit significant pore water flows. Steady flow of surface water over bed roughness features such as sand waves or pools and riffles can then drive water flow into and out of the shallow subsurface. This is often termed hyporheic exchange, and the subsurface region where mixing between stream and ground waters occurs is the hyporheic zone (Hynes, 1983). The hyporheic zone has been shown to be a critical com…     

EXPERIMENTAL STUDY OF BEDLOAD TRANSPORT IN UNSTEADY OPEN-CHANNEL FLOW

I.INTRODUCTIONBedloadtransportinsteadyuniformopenchannelflowhasbeenextensiVelystudied.Manyoftheformulasdevelopedforthepredictionofbedloadtransportinuniformopen-channelflowcanbebroughtinthefollowingform(ChienandWan,1983);ac=f(O)(l)xvhereacisthedimensionlessparameterofbedloadtranSPortandOisthedimensionlessparameterofflowintensity.TheseparametersaredefinedasfwheregsisthebedloadtranspoftratePerunitwidthindryweight;disthesedimentdiameter,Sisthebedslopeofthechannel;Rbisthehydraulicradiusdue…     

(Exergy)在湖泊生态系统建模中的应用

基于达尔文“适者生存”理论的热力学表述，本文把热力学概念“（Exergy）”作为一些重要模型参数的目标函数引入湖泊生态动力学模型．应用拥控制下的参数组合模拟程序实现了参数随时间的变化，并通过变化的模型参数来反映湖泊生态系统中物种组成和生态结构随时间的变化．这一改进克服了以往模型刚性较强、适应性差和生态系统特性考虑少的缺陷，该改进的湖泊生态动力学模型被成功用于滇池生态系统的模拟．     

CONTRIBUTION OF NITROGEN SPECIES AND PHOSPHORUS FRACTIONS TO STREAM WATER QUALITY IN AGRICULTURAL CATCHMENTS

The contribution from agricultural catchments to stream nitrogen and phosphorus concentrations was assessed by evaluation of the chemical composition of these nutrients in agricultural runoff for both surface and subsurface flow pathways. A range of land uses (grazed and ungrazed grassland, cereals, roots) in intensive agricultural systems was studied at scales from hillslope plots (0.5 m²) to large catchment (>300 km²). By fractionating the total nutrient load it was possible to establish that most of the phosphorus was transported in the unreactive (particulate and organic) fraction via surface runoff. This was true regardless of the scale of measurement. The form of the nitrogen load varied with land use and grazing intensity. High loads of dissolved inorganic nitrogen (with >90% transported as NH₄-N) were recorded in surface runoff from heavily grazed land. In subsurface flow from small (2 km²) subcatchments and in larger (>300 km²) catchments, organic nitrogen was found to be an important secondary constituent of the total nitrogen load, comprising 40% of the total annual load.     

INFLUENCE OF PIPE ANGLE ON BEDLOAD TRANSPORT IN AN INCLINED PIPE

1 INTRODUCTION Sedimentation in reservoirs is a significant problem. A variety of methods have been suggested to alleviate the effects of sedimentation, but none of the methods are inexpensive and entirely effective. Perhaps soil conservation is the best option, but soil conservation only leads to a reduction in sediment load. Dredging is expensive and produces a large amount of spoil. Sediment sluicing can be effective, but for large dams it takes a great deal of time to lower and re…     

APPLICATION OF OFF-LINE AND ON-LINE IDENTIFICATION TECHNIQUES TO BUILDING SEISMIC RESPONSE DATA

The objectives of this paper are to present a comparison of the dynamic characteristics of a seven-storey reinforced concrete building (Van Nuys–Holiday Inn) identified from four recorded strong-motion response data (Whittier earthquake, Landers earthquake, Big Bear earthquake and Northridge earthquake). In the analysis, time-domain methods for estimating the system parameters and the modal properties of the building are studied. Both off-line and on-line identification algorithms are applied to these seismic response data. Under the assumption of a linear time-invariant system the ARX model and ARMAX model are used. Comparison of the identification results using different models are made. In addition, recursive procedures are adapted as on-line identification and the time-varying modal parameters are estimated. For structural systems under strong earthquake excitation, a recursive identification method, adaptive forgetting through multiple models (AFMM), is introduced to identify systems with rapidly changing parameters. Through the analysis of the seismic response data of the building subjected to four earthquakes the identification algorithm and the identification results are discussed.     

NUMERICAL SIMULATION OF SEDIMENT TRANSPORT IN ALLUVIAL RIVER WITH FLOODPLAINS

1 INTRODUCTION The transport of sediment in rivers with active floodplains is a two-dimensional process because the main channel and the floodplain can have very different transport capacities. Therefore, two-dimensional (2D) models are often used to simulate the streamwise and transverse variations of sediment erosion and deposition. Many 2D numerical models have been presented to simulate sediment transport in floodplains (James, 1985; Pizzuto, 1987; Howard, 1992; Nicholas and Walli…