H11F-0343 0800h
Optimization and Uncertainty Estimates of WMO Regression Models for Precipitation-Gauge Bias in the United States
WMO (World Meteorological Organization) regression models for precipitation-gauge bias developed by Goodison et al.(1998) were optimized using the Very Fast Simulated Annealing algorithm. The regression-model uncertainties were estimated using a Bayesian Stochastic Inversion (BSI) algorithm. Legates and Willmott's (1990) precipitation correction factor database (applicable to average monthly conditions) was used as a target database to constrain selection of model parameters. The NLDAS (North American Land Data Assimilation System) Project database, containing daily wind speed and precipitation, was used as an input database for the WMO regression model in the United States. The results show that the optimal regression model is reasonable as its parameters are bounded by those of the WMO Alter-shielded model and unshielded model for both rain and snow. The temporal and spatial analysis of the precipitation correction factors calculated using the optimized regression model shows that they are relatively consistent with the results of Legates and Willmott (1990) in the United States. The advantage of the optimal regression model is that it is able to describe daily and interannual variation of precipitation correction factors. The relations among model parameters and model uncertainties, including regression parameter uncertainty and input data uncertainty, are examined. The results show that there are strong relations between regression model uncertainties and uncertain wind speed from the NLDAS database. Uncertainty of NLDAS data has little effect on optimization of the WMO regression model. However, it has significant effects on uncertainty estimates of the regression model parameters and the precipitation correction factors.
H11F-0344 0800h
Recession Flow Analysis for Selection of a Basin Drainage Model and Estimation of Basin-Wide Hydraulic Parameters
To guide us toward a correct description of the drainage processes in the coastal range of central Chile, we evaluated several analytical models for post-rainfall aquifer drainage: the Boussinesq model, various TOPMODEL expressions, and non-linear reservoirs. Based on discharge recession curves from one large basin and three sub-basins with areas on the order of 0.1, 1, 10 and 1000 km2, we argue for the Boussinesq model and against the TOPMODEL expressions and non-linear reservoirs, principally because all but the Boussinesq model would necessitate making non-physical assumptions to explain a significant portion of the recession curve. Although the Boussinesq model allows for estimation of hydraulic properties at the scale of the basins, uncertainty in the model parameters, including aquifer width, length of the drainage network, initial water table height, and drainable porosity, complicate the analysis. This uncertainty notwithstanding, reasonable values of the spatial parameters for the three smaller basins can result in values of saturated hydraulic conductivity (Ks) that are consistent with estimates from recovery tests of nearly 100 wells. However, the largest basin has a Ks about one order of magnitude greater using the same, albeit scaled, spatial parameterization. Though it would be easy to attribute this higher Ks to some sort of scaling phenomenon, there can be other interpretations. For example, we show how the same recession features at the largest scale can be recreated by assuming that the river network lies within a wide, highly-permeable fluvial deposition surrounded by material that is much less permeable.
H11F-0345 0800h
Storage-Dependent Drainable Porosity Implemented in the Hillslope-Storage Boussinesq Model: An application to Field Data From a Site in Northern Idaho, USA.
Specific yield is a parameter used to quantify the available amount of water for drainage. The instantaneous release of water from the aquifer during drainage however is determined by a related parameter, viz drainable porosity. In this work we present an analytical expression for drainable porosity as a function of water table depth and soil hydraulic parameters. This expression allows us to extend the hillslope-storage Boussinesq equation, recently introduced by the authors, to account for some of the effects of the unsaturated zone on dynamic hydrological behavior during free drainage from complex hillslopes. The concept of a storage-dependent drainable porosity is evaluated by comparing simulation results to field data, which were obtained from a site in Troy, Idaho, where a shallow silt loam soil layer is overlying a fragipan. Evaluation of the model is based on measurements of water table height, soil moisture and outflow. The field site is characterized by the influence of macropores, a decreasing saturated hydraulic conductivity with depth, and a small drainable porosity. Modeling of these data involved making the saturated hydraulic conductivity a function of the depth to the water table, and allowing for variable precipitation inputs.
H11F-0346 0800h
Impacts of Land Cover and Land-use Change on the Water and Energy Cycle of the Great Lakes Region
The rate of land use change in recent centuries is much faster than that in the past. Much of the pre-settlement forestation in the Great Lakes region has been harvested and converted to agricultural land uses or early successional forests. This has resulted in large-scale water and energy cycles changes in the region. It is therefore important to understand the impacts of historical land cover and land-use change, to put ongoing modifications into the proper context. The focus of this study is to explore how land-use changes from pre-settlement to modern vegetation in three Great Lakes states: Minnesota, Wisconsin, and Michigan; have affected the hydrologic cycle in the region. The Variable Infiltration Capacity (VIC) model is used to study water and energy fluxes at 1/8 degree resolution in the Great Lakes region. Land Data Assimilation System (LDAS) meteorological and soil data as well as pre-settlement and modern vegetation data resulted from the USGS Land Use History of North American (LUHNA) were used as model input. The model simulated water and energy fluxes under pre-settlement and modern vegetation conditions using 50 years of meteorological forcings. Results were compared between the simulations to assess the impacts of land-use change on water and energy fluxes. Simulations indicate that deforestation has played a large role in changing the hydrologic response of the basin to cold season processes (snow and soil frost) as well as in the year round storage of soil moisture and generation of runoff. This large-scale hydrology study will provide the basis for further research on climate change, frozen soil and cold season processes over the entire Great Lakes region.
H11F-0347 0800h
On the effects of triangulated terrain resolution on distributed hydrologic model response
Distributed hydrologic models based on triangulated irregular networks (TIN) provide a means for computational efficiency in small to large-scale watershed modeling through an adaptive, multiple resolution representation of complex basin topography. Despite previous research with TIN-based hydrology models, the effect of triangulated terrain resolution on basin hydrologic response has received surprisingly little attention. Evaluating the impact of adaptive gridding on hydrologic response is important for determining the level of detail required in a terrain model. In this study, we address the spatial sensitivity of the TIN-based Real-time Integrated Basin Simulator (tRIBS) in order to assess the variability in the basin-averaged and distributed hydrologic response (water balance, runoff mechanisms, surface saturation, groundwater dynamics) with respect to changes in topographic resolution. Prior to hydrologic simulations, we describe the generation of TIN models that effectively capture topographic and hydrographic variability from grid digital elevation models. In addition, we discuss the sampling methods and performance metrics utilized in the spatial aggregation of triangulated terrain models. For a 64 km2 catchment in northeastern Oklahoma, we conduct a multiple resolution validation experiment by utilizing the tRIBS model over a wide range of spatial aggregation levels. Hydrologic performance is assessed as a function of the terrain resolution with the variability in basin response attributed to variations in the coupled surface-subsurface dynamics. In particular, resolving the near-stream, variable source area is found to be a key determinant of model behavior as it controls the dynamic saturation pattern and its effect on rainfall partitioning. A relationship between the hydrologic sensitivity to resolution and the spatial aggregation of terrain attributes is presented as an effective means for selecting the model resolution. Finally, the study highlights the important effects of terrain resolution on distributed hydrologic model response and provides insight into the multiple resolution calibration and validation of TIN-based hydrology models.
H11F-0348 0800h
SPARSE LEARNING MACHINES FOR CHAOTIC DYNAMIC SYSTEMS
Sparse learning machines provide a viable framework for modeling chaotic time-series data. A powerful state space reconstruction methodology using both Support Vector Machines (SVM) and relevance vector machines (RVM) within a multi-objective optimization framework is presented in this paper. The utility and practicality of the proposed approaches have been demonstrated on the time series of the Great Salk Lake (GSL) biweekly volume change from 1848 to 2004. A comparison of the two methods is made based on their predictive power and robustness. The reconstruction of the chaotic dynamics of the Great Salt Lake volume time series is attained using the most relevant feature subset of the training data. In this paper, efforts are also made to assess the uncertainty and robustness of the machines in learning and forecasting as a function of model structure, initial conditions, and bootstrapping samples. The resulting model will normally have a structure, including parameterization, that suits the information content of the available data, and can be used to develop time series forecasts for multiple lead times ranging from two weeks to several months.
H11F-0349 0800h
Implementation of Particle Tracking to a Physically Based Hydrologic Model and Implications for Calibration
Physically based hydrologic models, when properly applied, provide the framework to easily evaluate baseflow and interflow contributions to total runoff. However, the data available for the calibration procedure are often limited to streamflow and only under the best conditions a few point measurements of groundwater heads and soil moisture values are available to enhance the procedure. A methodology of incorporating particle tracking into a fully distributed hydrologic model is investigated as the means of providing an extra layer of calibration data and increased confidence in overall model performance. The objective of this research is to determine if such a combined model formulation can be used to improve model calibration and under what conditions is this formulation beneficial. The implications for quantifying contributions of "old" versus "new" water to increased runoff are also evaluated.
H11F-0350 0800h
Geomorphology Toolbox for Assessing the Potential Effects of Land-use Change and Management Practices on Stream Form and Integrity
An important contribution that engineers and geomorphologists can make to environmental management is to develop techniques that empower non-specialists to make rational planning decisions within the context of a changing environment. Existing models can be used to assess the potential hydrologic effects of land-use change on receiving waters, but practical tools for translating these results into predictions regarding channel stability and effects on stream biota are currently unavailable to local planners. To improve watershed management in the context of changing land uses, we present a flexible, changeable package of mechanistic and statistical models to provide estimates of long-term changes in stream erosion potential, channel processes, and instream disturbance regime. These models are developed in Visual Basic for Applications/ Excel and contains a suite of stream / land-use management modules that are designed to operate with either continuous or single-event hydrologic input in a variety of formats. Based on input channel geometry and flow series, the various modules provide users with estimates of the following characteristics for pre- and post-land use change conditions: (1) the temporal distribution of hydraulic parameters including shear stress, specific stream power, and potential mobility of various particle sizes; (2) effective discharge / sediment yield; (3) potential changes in sediment transport and yield as a result of altered flow and sedimentation regimes; (4) frequency, depth, and duration of bed scour; (5) several geomorphically relevant hydrologic metrics relating to channel form, flow effectiveness and "flashiness". An attractive feature of this approach for stormwater management is a set of user-friendly tools to examine time-integrated sediment transport and scour characteristics across a range of flows and time periods associated with varying stormwater mitigation schemes. These modules give end users a suite of tools to compare the erosive potential of hydrographs, to depict channel changes that might result from different land-use management scenarios, and to improve interpretation of biomonitoring information through quantification of stream disturbance regimes.
H11F-0351 0800h
Rice Straw Compost as a Soil Amendment for the Reduction of Surface Runoff in Almond Orchards in Glenn County, California
Almond production in the Northern Sacramento Valley is dependant on dormant season pesticide application and fertilizers. However, over the past 10 years there has been increased demand from public and regulatory agencies for farmers to reduce the movement of agricultural chemicals into local water sources. Many pesticides of concern have been detected in California watersheds particularly after runoff producing storm events. Two methods of reducing surface runoff into local waterways are to increase orchard soil infiltration rates, and to use riparian buffers to reduce surface flow velocity or runoff that does occur. Organic rice straw compost was applied in an orchard to examine its effect on soil infiltration and runoff. A rainfall simulator was developed capable of producing a 2.54 cm per hour storm and covering an area roughly 3 meter diameter. Runoff and infiltration are being tested from three orchard cells with the compost addition and three orchard cells without. Infiltration and runoff are also being monitored at three plots in a nearby riparian buffer strip. Runoff samples are being analyzed for nutrients, pH, EC and aqueous carbon content.
H11F-0352 0800h
Parameterising a semi-distributed hydrological model from hillslope and catchment geomorphology
The geomorphic structure of landscapes controls the hydrological response in a number of ways: hillslope length controls total amounts of water supply to footslope areas; hillslope curvature controls acceleration and/or convergence/divergence of flow paths; soil cover thickness distribution controls subsurface water transport capacity; channel network topology controls the geomorphic dispersion of channel flow, etc. Although this has been known for a long time, there are many open questions relating to the use of morphometric information in hydrological modelling. One of the fundamental questions of hydrogeomorphology is how an understanding of the spatial structure of hillslopes and catchments can be used to help parameterising semi-distributed hydrological models. In these models, the two-dimensional spatial domain is collapsed to a one-dimensional profile. The ordinate of these profiles can be the downhill-distance-towards-the-channel (e.g.\ within the hillslope-storage Boussinesq model [{\it Troch et al.} (2003), {\it Water Resour. Res.}, {\it 39}(11), 1316, doi:10.1029/2002WR001728.]) or any other `similarity' index, such as the topographic index (e.g.\ within TOPMODEL) On this poster, we present results of morphometric analyses of various physiographic regions within the US, and an application of the hillslope-storage Boussinesq model to a field site in Troy, ID. Topics addressed include: the spatial distribution and connectivity of hillslope curvature; hillslope outline shape vs. internal curvature; the landscape treated as one large hillslope folded around the channel network; and disequilibrium between hillslope morphology and current channel network extent.
H11F-0353 0800h
A Framework for the Development and Analysis of Parsimonious Watershed Models
Relatively simple (parsimonious) watershed models are often adequate for many modeling objectives, e.g. flood forecasting or low-flow predictions. They can yield similar performances as more complex models, but have better identified parameters which makes them easier to calibrate and more suitable for regionalization studies, i.e. a potential application to ungauged watersheds. We present a Matlabr toolbox combining a modular framework for parsimonious watershed modeling with an analysis tool that allows for sensitivity and uncertainty analysis in a Monte Carlo framework. The modular modeling environment makes the toolbox ideal for comparison and ensemble forecasting studies including multiple model structures. Several case studies in which the tool is applied to a variety of hydrologically very different watersheds will be presented. The watersheds range from humid to semi-arid, and from fast responding clay to ephemeral chalk.
http://ewre-www.cv.ic.ac.uk/software/toolkit.htm
H11F-0354 0800h
Comparison Between SSM/I Filtering Algorithm and Neural Networks for Snow Cover Identification in the Northern Midwest States
Snow coverage and depth are two key parameters that are essential to be estimated and applied in a wide range of hydrological applications. However, the traditional field sampling methods and the ground-based data collection are often very sparse, time consuming, and expensive compared to the coverage provided by remote sensing techniques. Passive microwave remote sensing data have been investigated by numerous researchers and have been demonstrated to be effective for monitoring snow pack parameters. Those researches have resulted that the microwave brightness temperature are related to the snow cover structure with different correlation degrees. The primary objective of this research is to produce a spatial estimation of snow water equivalent with sufficient spatial and temporal resolution using passive microwave data. The final product of this project will be an additional tool for flood warning and water resource forecasts, which can be an additional input to the actual hydrological models. The focus of this paper is to investigate the performance of filtering algorithm (developed by NESDIS NOAA) and Neural Network algorithm for snow cover identification in the Northern Midwest States. Artificial neural networks have been successfully applied to image processing, and have shown a great potential in the classification of a wide range of remote sensing data. The study area is located in the Northern Midwest of the United States within $109\deg$$30\prime$W - $100\deg$$50\prime$W and $48\deg$$40\prime$N - $41\deg$$00\prime$N. A total of 180 ground stations covering the study area have been identified for this experiment. The passive microwave data from the current SSM/I (Special Sensor Microwave Imager) sensors on board the DMSP F13 and F14 satellites are used in both ascending and descending orbits. These images provide (twice-a-day) measurements of the brightness temperature in seven channels with different frequencies and polarizations (19 V, 19 H, 22 V, 37V, 37 H, 85 V, and 85 H). All the seven channels were tested in this project. The preliminary results showed that the filtering algorithm performance in identifying the non-snow pixels was acceptable with accuracy varying between 79% and 99% for both ascending and descending modes. However, the performance in identifying snow pixels was very poor.
H11F-0355 0800h
The Effects of Future Irrigation Projects on Crop Water Requirements in Southeastern Turkey - Implications for Planning and Management
We investigated the feedback between changes in potential evaporation and future irrigated acreage in Southeastern Turkey using observed and simulated meteorological variables. Under the framework provided by the Complementary Relationship, the results of our research demonstrate the existence and quantify the magnitude of scale-dependence in the relationship between irrigated area and the amount of water required per unit area. Assuming that the changes in future evaporation conditions will be similar to the observed changes, water use for irrigation is expected to decrease over 50 percent in selected irrigation sites. This study lends credibility to the hypothesis, which suggests that future land use modifications in the form of irrigated agriculture in Southeastern Turkey have the potential to strongly affect potential evaporation - a key parameter influencing the amount of water required for irrigation. Incorporating this decrease in overall planning of future irrigation projects could lead to significant water savings and improve sustainability of water resources in the region.
H11F-0356 0800h
Effects of initialization conditions in distributed hydrological response: spatio-temporal dependencies on rainfall forcing, watershed topography and soils.
Numerical experiments with hydrological models show that the initial conditions are important in modeling the rainfall-runoff response at the event scale. However, it is still largely unknown how the influence of initialization states is related to land-surface characteristics such as catchment topography and soils. Similarly, different rainfall forcings may lead a variety of dependencies of the hydrologic response on antecedent wetness conditions. We investigate the influence of the initial states on the short-term hydrologic estimation to characterize the integral effects of topography and soils across a range of precipitation rates using a physically-based, distributed-parameter hydrological model tRIBS (TIN-based Real-time Integrated Basin Simulator). The tRIBS model accounts for the processes of rainfall interception and evapotranspiration with the continuous soil moisture accounting, lateral moisture transfer in the unsaturated and saturated zones, and runoff routing. In the discussed study, we assume that the groundwater significantly controls the initial conditions of the basin and, therefore, that the mean water table depth is the primary initialization variable. Initialization of the soil moisture distribution in the unsaturated zone is thus assumed to be uniquely related to the water table position. Two case studies have been developed. The first one considers a synthetic 2-D planar hillslope for which the effects of different initializations are studied for various slope magnitudes and soil types subject to different rainfall rates and durations. The second one is based on the real basin, Baron Fork (OK), for which the topography and soil/landuse types are fixed while different initial water table positions and synthetic rainfall events are used. The study focuses on the analysis of dynamic and time-integrated links between the catchment land-surface descriptors and a number of key hydrologic variables controlling the basin response. A variety of spatially-lumped, e.g. runoff types comprising the outlet streamflow, and spatially distributed variables, e.g. the root zone soil moisture, are used to examine the transition of the dominant response mechanisms, the basin areas of higher sensitivity, and the contributing factors to the dissipation of the initialization effects. The discussed cases demonstrate the interplay between different hydrological processes leading to a complex structure of effects that initialization states impose on the basin response.
H11F-0357 0800h
Rainfall-Runoff Interaction in Shallow Flows and Its Effect on Rill Erosion
Rill erosion is a dynamic process consisting of the detachment and transport of soil materials by concentrated flow. A considerable amount of soil is lost in this form in many parts of the world, causing both on-site and off-site problems. Rill erosion does not occur as an isolated process in nature. In fact, while detaching and transporting soil, raindrops impact the flow causing some of the flow characteristics to change. However, the information on this interaction is not well known or not readily available. The objective of this study was to evaluate the rain-runoff interaction and its effect on the process of rill erosion. The methodology included the evaluation of two rainfall intensities, three different slopes and four different inflow rates, with three replicates, in a simulated rill. Rainfall was applied with a Norton type rainfall simulator. In general, it was observed that rill erosion detachment rate due to runoff alone was greater for increasing values of rainfall intensity, slope and discharge. Rill erosion factor, Kr, defined as the rate of soil detachment per unit of hydraulic shear stress, tau, was greater for the rain-runoff interaction than it was for the runoff alone. Critical shear stress, tau-c, or the value at which initiation of detachment occurs was greater for higher intensities and slopes and for the interaction of rain-runoff. The Mean Weigh Diameter (MWD) of sediments was only significantly different for the interaction rain-runoff for the 16 percent slope and inflow rates of 6 liters per minute (lpm). No significant differences were found for the rest of the treatments. Most of the sediments under low rain intesities and gentle slopes had an average MWD of 0.13 mm. This value increased up 1.50 mm for the high inflow rate and slope. In conclusion, rill erosion increased significantly due to the interaction of rain and runoff and the effect was greater for steeper slopes and higher rainfall intensities. This interaction must be considered in soil erosion models to make a better prediction of this water erosion process.
H11F-0358 0800h
Development of Rainfall Time Distributions for Design Floods
In the present study a new method is proposed for the determination of time distribution of design rainfall in estimating the design flood of a watershed by a rainfall-runoff model. The mean hourly rainfall data series of the watershed were first established for the whole duration of data period by averaging the concurrent rainfall data recorded at the rain gauging stations within or nearby the watershed using the Thiessen's method. Then, from the averaged rainfall data series for the watershed the rainfall amounts with a specified rainfall duration were arrayed in a descending order, resulting an annual exceedance time series. The dimensionless cumulative rainfall corresponding to each element of the exceedance series were plotted against time for specified durations. A series of representative cumulative rainfall curves were developed by assigning the probability (10% - 90%) of occurrence of each element by plotting position formula, i.e., California formula. These curves were used to select the most appropriate time distribution of design rainfall which results the maximum peak discharge by a rainfall-runoff model. The method developed were applied to actual flood events occurred in Moohan River and Chengge River basins. The shape of rainfall hyetographs showed more randomness than other empirical distributions such as Huff and Mononobe distributions. And, the design floods estimated by Clark's watershed routing method using the time distribution developed in this study were also much more closer to the observed values than using other time distributions of rainfall.
H11F-0359 0800h
Simulation of Spring Snowmelt Runoff by Considering Effect of Local Topography on Snow Cover and Freezing/Thawing Soil Layer in Kushiro Mire
The NIES Integrated Catchment-based Eco-hydrology (NICE) model [Nakayama and Watanabe, 2004] was expanded to consider the effect of the snow layer and the freezing/thawing soil layer on spring snowmelt runoff in the Kushiro River catchment, Japan (NICE-2). Snow/freezing model was expanded including the effect of local topography and meteorology, and surface runoff mode was expanded to two-layer model of freezing/thawing soil layers. The NICE-2 reproduced well the measured values of snow depth, soil moisture, soil temperature, groundwater level, and river flow discharge throughout the year, showing that this model achieves high accuracy and that the mechanism of spring snowmelt runoff is related to changes in soil structure, soil temperature, soil moisture, and groundwater level. In particular, soil frost alters the hydraulic character of soil by restricting infiltration in the coldest part of winter, increasing pore size after the thawing process, and creating macropores and desiccation cracks in the soil. The effect of the spring snowmelt runoff on sediment-load influx and nutrient infiltration is very important because the spring snowmelt runoff is a significant component of the water balance in this catchment and the soil structure changes dramatically during this period. The drying phenomenon in the Kushiro Mire is closely related with the increased influx of sediments from the surrounding area, where agricultural development, reclamation, and channelization of the river occurred [Nakayama and Watanabe, 2004]. In future work, the NICE-2 can simulate the relation between water and sediment influx to the mire by including the mass transfer process, which will be very important in protecting the sediment loads from riparian forests, and in predicting the recovery of a mire ecosystem by re-meandering the channelized rivers. [Reference] Nakayama, T., and M. Watanabe, Simulation of drying phenomena associated with vegetation change caused by invasion of alder (Alnus japonica) in Kushiro Mire, Water Resour. Res., Vol.40, No.8, W08402, 2004.
H11F-0360 0800h
Impervious Surface Assessment of the Towne Creek Watershed, Etowah County, Alabama
A Geographic Information System (GIS) based approach was used to do a preliminary assessment of a watershed's vulnerability and has been proven to be a quick, inexpensive, and effective means to provide guidance to the watershed manager. This GIS-based approach was used in an assessment of a watershed's proportion of impervious surface as a quantifiable measurement its vulnerability. The percent of a watershed area that is impervious was determined by utilizing the Impervious Surface Analysis Tool (ISAT), which is an extension of the ArcGIS program. ISAT uses landuse/landcover, watershed boundary, and population density data sets to calculate the percent impervious surface (%IS). The Towne Creek watershed covers 24,730 acres in southern Etowah County, Alabama, was investigated. The watershed, which empties into the Middle Coosa River, includes the suburbs of the City of Gadsden. The watershed was delineated into 75 catchments ranging from 230 to 3,163 acres. Initial assessment of the watershed estimated 10.5% of the area is impervious. Individual catchments within the watershed were then classified as being degraded ($>$25 %IS), impaired (10 to 25 %IS) or protected ($<$10 %IS). According to this classification scheme, 5 catchments covering 2.6% of the watershed is classified as being degraded, and 5 catchments covering 3.6% of the watershed is impaired, and the remaining 65 catchments covering 93.8% of the watershed is protected.
H11F-0361 0800h
Space-Time Daily Rainfall Generation Model in the Subtropical Region
Daily rainfall is an essential input to hydrologic models that are invaluable tool for evaluating various Everglades restoration projects. In many cases, we used only a limited length of historical rainfalls (<30 years) which is not enough to define extreme hydrologic events such as 1-in-10-year droughts. Thus, it is desirable to use synthesized long-term rainfalls to quantify an uncertainty in hydrologic simulations. The synthetic rainfalls data can be generated by a simple stochastic process for the sake of an intensive and expensive numerical climate models. In general, the previous daily rainfall models consist with two components: occurrence and amounts processes. The occurrence process has been formulated typically by a lag-one, two-state Markov process. Then, rainfall amounts are generated by a separate process. However, this approach could not incorporate the spatial dependence of both occurrence and amounts. Daily rainfalls in south Florida show that the space-time correlation is somewhat significant (rs ,d 0.5). Thus, it is reasonable to introduce the dependence structure in a model. We use a concept of rain storm clustering process to describe adequately the space-time correlation structure that is appeared on the subtropical rainfalls which are driven primarily by convective activities. In our proposed model, a convective storm cluster is randomly identified from the observed probabilities of occurrence on a day. The storm cluster contains gauges where rainfall activity occurs. The rainfall amounts are generated based on the acyclic spatial dependence on wet days. This is a way of considering the spatial intermittence of daily rainfalls. In specific, the temporal dependence of rainfall occurrence is accounted by the Markov process of the rainfalls that are not included in a storm cluster. This study tests the proposed model with historical rainfalls measured from 78 stations in south Florida. Various sample statistics are used to validate the model.
H11F-0362 0800h
Modelling the Hydrological Performance of Stormwater Management Retention Ponds in Scotland
The work presented here is part of a wider modelling study into the long-term performance of Sustainable Urban Drainage Systems in Scotland, a stormwater management technique employed by the Scottish Environment Protection Agency to protect watercourses from flooding and water quality deterioration. In particular, the study aims to predict how retention ponds perform under varying inflow conditions and climate change scenarios to assess the long-term impact of this form of stormwater management on Scotland's future water resources. A suite of simulations was conducted to explore the flow attenuation characteristics of conical retention ponds that have outflows controlled by triangular notch weirs. The inflows were represented as triangular hydrographs using a range of peak flows. Optimum flow attenuation occurs when peak outflow is reduced and hydrograph time lags are prolonged. Analysis of the results has shown that the Temporary Storage Volume available in the retention pond during any given storm exercises a critical control on flow attenuation performance of the pond. Factors which increase Temporary Storage Volume such as increasing pond radius, decreasing water level at the start of a storm, decreasing pond side slope gradient and increasing weir crest elevation lead to a marked improvement in pond flow attenuation performance. Conversely, factors which decrease Temporary Storage Volume result in poor flow attenuation performance. These simulations also demonstrate the secondary control that weir angle has on flow attenuation performance through its influence on the Dynamic Storage Volume, which is only effective once outflow through the weir has begun. Larger weir angles reduce the flow attenuation performance of ponds; however caution must be exercised in using smaller weir angles, which despite improving performance, may lead to an increased risk of overtopping. Other simulations show that ponds suffer a reduction in performance when subject to larger inflow volumes and that the provision of an additional outflow device can have a marked, but complex, effect on performance. With regard to the latter, for example, a low-level orifice outlet may decrease flow attenuation (by increasing the peak outflow and decreasing lags), but will decrease the risk of the pond not being well drawn down at the start of the next storm. Clearly, there is a trade off between the attenuation of a current and a subsequent storm. Although these trends are not unexpected, there is little published information that quantifies them in such a way that the performance of a retention pond can be predicted over the range of conditions likely to be encountered during its operating life. The generation of performance curves from the simulations being carried out in this study should lead to a better design process for retention ponds, for both single-event and event sequence scenarios.
H11F-0363 0800h
An Automated Correction Technique for Weighing Type Bucket Rain Gauge Measurements
Accurate precipitation data is one of the most important inputs for hydrological modeling. Errors in precipitation records from weighing type bucket rain gauges may be introduced from missing data, bucket decanting, wind and electronic sensor drift. Manual correction of these errors in precipitation data records can be extremely tedious and time consuming. An automated methodology for correcting the errors has been developed and applied at two weather stations located in the Dry Creek watershed near Boise ID for years 2000-2003. The method uses the MatLab code to correct the hourly precipitation by scanning the data on a 24 hours moving window. The method was successful at filtering periodic and instantaneous noise to provide useful and realistic hourly rainfall records for input to surface hydrological models. The corrected cumulative annual precipitation was within 96 to 99% of the measured annual total precipitation. The incremental record may then easily be scaled to match the measured annual total precipitation at the user's discretion.
H11F-0364 0800h
Spatial and Temporal Variability of Hydraulic Properties in the Russian River Streambed, Central Sonoma, County, CA
Temporal and spatial variations of flux and vertical hydraulic conductivity were measured in the Russian River streambed in Sonoma County, California. In-situ vertical hydraulic conductivity measurements were made using a modified seepage meter, equipped with mini-piezometers and sediment was collected with a bucket and shovel. We sampled three different streambed (near bank, midpoint, and thalweg) locations at five different sample locales throughout the river system. Vertical hydraulic conductivity of the streambed ranged from 8.55X10$^{-5}$ cm/sec to 1.52X10$^{-1}$ cm/sec. Flux varied from -240 to 600 cm/day, which indicates both gaining and losing reaches of the stream occur in our study area. There was not a strong correlation (r=0.08) between particle size distribution and vertical hydraulic conductivity. Our findings will assist the Sonoma County Water Agency in managing water needs for the citizens of Sonoma County.
H11F-0365 0800h
Enhanced Thematic Mapper Plus Analyses of Chlorophyll-a Concentration and Distribution in Small Kettle Lakes, Southern Minnesota
Spatial and temporal variability of lake water quality is well defined; however, due to costs and logistical constraints, multiple assessments of water quality are rarely obtained in Minnesota lakes. For improved resource management, an integrated assessment of whole-lake surface water quality is needed. Sequential spatial descriptions of water quality variability will facilitate characterizing physical, chemical, and biological processes in lakes and help to identify sources of external and internal nutrient loading within individual lakes. Our study focused on surface water properties in six small southern Minnesota meso-eutrophic, eutrophic, and hypereutrophic lakes. Our protocol included obtaining multiple, georeferenced in-lake and laboratory-based assays of surface water quality within 24 hours of each Enhanced Thematic Mapper Plus (ETM+) overpass during the summer of 2001. Lake water data (including chlorophyll-a, total phosphorus, water transparency, and total suspended solids) were regressed against temporally and spatially equivalent three-by-three pixel averages of singular and combined ETM+ spectral bands. A simple linear regression of chlorophyll-a analyses from water samples and corrected ETM+ Band 2 data provided the strongest correlation (R$^{2}$ = 0.96) among the available data. The chlorophyll-a concentrations from processed ETM+ data in each lake exhibit up to three orders of magnitude greater variance than those derived from water sample data. Furthermore, ETM+ results illustrate distinctive patterns of chlorophyll-a distribution among lakes of similar trophic status that are not present in water sample data. Thus, it appears ETM+ data provide better characterizations of overall chlorophyll-a concentrations and distribution relative to multiple-sample in-lake water analyses in small kettle lakes.
H11F-0366 0800h
Physical and Chemical Characteristics of Lakes in the Central Yakutian Lowlands, Russia
The Republic of Yakutia is located in the north-eastern part of Russia. In the central part of Yakutia, there are approximately 106,000 lakes which cover an area of ca. one million hectare and have an approximate volume of more than 180 billion m3. The current limnological research work carried out in Central Yakutia is in the frame of a larger project aiming in the reconstruction of the regional environmental history using aquatic organisms. The limnological part of this project provides the basis to study the relationships between aquatic organisms and their environments, which is essential to derive transfer functions for the reconstruction approach. The results shown on this poster are based on two expeditions during summer 2003 and 2004, in which 47 lakes from two regions in the Central Yakutian Lowlands were sampled. The lake water samples were analysed for electrical conductivity, pH, oxygen, lake water depth, secchi depth, water temperature, ionic concentrations, nutrients, dissolved organic and inorganic carbon. The results of the measurements were used to classify the lakes in order to find systematic patterns in terms of geology, anthropogenic impacts, land use, vegetation and regional climate.
H11F-0367 0800h
Reduced Complexity Modelling of Urban Floodplain Inundation
Significant recent advances in floodplain inundation modelling have been achieved by directly coupling 1d channel hydraulic models with a raster storage cell approximation for floodplain flows. The strengths of this reduced-complexity model structure derive from its explicit dependence on a digital elevation model (DEM) to parameterize flows through riparian areas, providing a computationally efficient algorithm to model heterogeneous floodplains. Previous applications of this framework have generally used mid-range grid scales (10$^{1}$-10$^{2}$ m), showing the capacity of the models to simulate long reaches (10$^{3}$-10$^{4}$ m). However, the increasing availability of precision DEMs derived from airborne laser altimetry (LIDAR) enables their use at very high spatial resolutions (10$^{0}$-10$^{1}$ m). This spatial scale offers the opportunity to incorporate the complexity of the built environment directly within the floodplain DEM and simulate urban flooding. This poster describes a series of experiments designed to explore model functionality at these reduced scales. Important questions are considered, raised by this new approach, about the reliability and representation of the floodplain topography and built environment, and the resultant sensitivity of inundation forecasts. The experiments apply a raster floodplain model to reconstruct a 1:100 year flood event on the River Granta in eastern England, which flooded 72 properties in the town of Linton in October 2001. The simulations use a nested-scale model to maintain efficiency. A 2km by 4km urban zone is represented by a high-resolution DEM derived from single-pulse LIDAR data supplied by the UK Environment Agency, together with surveyed data and aerial photography. Novel methods of processing the raw data to provide the individual structure detail required are investigated and compared. This is then embedded within a lower-resolution model application at the reach scale which provides boundary conditions based on recorded flood stage. The high resolution predictions on a scale commensurate with urban structures make possible a multi-criteria validation which combines verification of reach-scale characteristics such as downstream flow and inundation extent with internal validation of flood depth at individual sites.
H11F-0368 0800h
Anatomy of a Flash Flood in the Amargosa Desert, U.S.A.
In August 2004, intense convective rainstorms caused flash flooding throughout the Amargosa River drainage network, temporarily closing Death Valley National Park and causing two fatalities when runoff from Furnace Creek and other channels overtopped roadways in the Park. In 1998, we began installing streambed temperature loggers, pressure transducers, and scour chains in the normally dry channel and selected tributaries of the river in the Amargosa Desert and Oasis Valley. The primary objective of this work is to improve understanding of ground-water recharge from ephemeral streamflows under current climatic conditions. Two weeks after the flash flooding, we visited instrumented sites and estimated peak flows by surveying high-water marks and corresponding channel geometries. Time series of temperatures and stages, together with peak-flow estimates, reveal the routing and evolution of distinct flood pulses in the upper Amargosa River basin. The data also reveal previously undocumented details of individual flash-flood hydrographs, including initial and subsequent flood pulses at two sites. Arid environments are prone to flash flooding not only because vegetation is sparse, but also because the surface-water network is decoupled from underlying ground water by a thick unsaturated zone. Nonlinear interactions between runoff (with energy potentials on the order of a meter of head) and the unsaturated zone (with energy potentials on the order of negative hundreds of meters of head) keep advancing fronts of flood pulses sharp. Profiles of water content beneath the main channel before and after the passage of a flood pulse, together with down-channel attenuation of flow volume within individual pulses, show the leaky nature of dry alluvial channels and the efficiency at which flash floods become potential recharge.
H11F-0369 0800h
A New Method to Evaluate Streamflow Recovery After a Drought
Under conditions of environmental change, occurrences of drought are expected to increase in number and severity. A river basin does not behave linearly to precipitation, and many drought indices, such as the Palmer Drought Severity Index (Palmer, 1965), are based on meteorological conditions, since they were developed for agricultural purposes rather than hydrological behavior of a river basin. A new method is presented to answer the question "When does the streamflow recover to normal conditions after a drought?", a question raised by many water managers who rely on adequate streamflow and reservoir levels, particularly municipalities, industry, power stations, and irrigation districts. The recession index is an indicator for the overall water basin conditions, and integrates all streamflow generating conditions, including the status of groundwater, wetlands, and basin wetness (or antecedent watershed conditions). The method is based on recession analysis of daily streamflow utilizing the RECESS program (Rutledge, 2004). The recession index K is calculated for all streamflow available records. Analysis of recession indices of streamflow in the Battle River Basin, a prairie watershed in central Alberta, Canada, was carried out using a minimum length of recession curves of 5 days. The analysis reveals drought years have associated low median annual K values, measured in days per log cycle, while normal to wet years have high median annual K values. The suggested method can be used to evaluate the overall status of a river basin in terms of runoff conditions by relating the latest measured recession index to the historical record. This gives an indication if, in terms of streamflow response, a river basin is still in a drought, in a phase of recovery, or fully recovered. Water managers can then predict water availability for the coming months. References: Palmer, W. C, 1965: Meteorological Drought. Res. Paper No.45, 58pp., Dept. of Commerce, Washington, D.C. Rutledge, A.T. and Mesko, 1996, Estimated hydrologic characteristics of shallow aquifer systems in the Valley and Ridge, the Blue Ridge, and the Piedmont physiographic provinces based on analysis of streamflow recession and base flow: U.S. Geological Survey Professional Paper 1422-B, 58 p. Rutledge, A.T. 2004 Program user guide for RECESS. water.usgs.gov/ogw/recess/UserManualRECESS.pdf
H11F-0370 0800h
The Urban Drainage Network and its Control on Extreme Floods
In urban watersheds, where first order streams have been truncated and replaced by subsurface storm drain networks and vegetation has been replaced by impervious surface, overland travel velocities and runoff volumes are much greater than in predevelopment conditions. Management facilities, such as detention and retention basins, are used to mitigate the adverse impacts of urbanization, including increasing flood peaks and runoff volumes. We present analyses of hydrologic response in Dead Run, a 14.3 sq. km. watershed in the Baltimore metropolitan area, based on a detailed, digital reconstruction of the storm drain network, hydrologic observations in the basin and a hydrologic/hydraulic modeling system. Analyses center on a storm which produced record flooding in Dead Run on 7 July 2004. Model analyses directly incorporate the hydrologic and hydraulic controls of the drainage network (both the surface drainage network and the storm drain system) and those of detention basins. Analyses utilize rainfall observations derived from weather radar and a network of 19 rain gages, as well as stream gaging observations (at 1 - 5 minute time interval) from 6 stations. The effectiveness of the storm drain network to quickly and efficiently remove storm runoff from the ground surface, in conjunction with the stormwater management basin's ability to attenuate flood peaks, is examined at both the local and watershed scale. Analyses focus on events, like the 7 July 2004 event, which have long return intervals.
H11F-0371 0800h
Hydrologic Drought in the Colorado River Basin
This paper focuses on drought scenarios of the Upper Colorado River Basin (UCRB) for the last five hundred years and evaluates the magnitude, severity and frequency of the current five-year drought. Hydrologic drought characteristics have been developed using the historical streamflow data and tree ring chronologies in the UCRB. Historical data include the Colorado River at Cisco and Lees Ferry, Green River, Palmer Hydrologic Drought Index (PHDI), and the Z index. Three ring chronologies were used from 17 spatially representative sites in the UCRB from NOAA's International Tree Ring Data. A PCA based regression model procedures was used to reconstruct drought indices and streamflow in the UCRB. Hydrologic drought is characterized by its duration (duration in year in which cumulative deficit is continuously below thresholds), deficit magnitude (the cumulative deficit below the thresholds for consecutive years), severity (magnitude divided by the duration) and frequency. Results indicate that the current drought ranks anywhere from the 5th to 20th worst drought during the period 1493-2004, depending on the drought indicator and magnitude. From a short term perspective (using annual data), the current drought is more severe than if longer term average (i.e., 5 or 10 year averages) are used to define the drought.
H11F-0372 0800h
Hydrometeorology of Extreme Flooding in a Small Urban Watershed
A multicell thunderstorm system on 7 July 2004 produced record flooding in the 14.3 km2 Dead Run watershed, which drains an urbanized portion of the Baltimore metropolitan region. Storm total accumulations of 100 - 130 mm during a period of less than 2 hours resulted in flood peaks that exceeded those produced in 1972 by Hurricane Agnes. Analyses of the 7 July 2004 thunderstorm system focus on the spatial and temporal variability of rainfall at scales relevant to flash flooding in small urban watersheds. Spatial scales of interest extend below 1 sq. km and the time scales of interest are typically less than 60 minutes. Analyses are based on volume scan reflectivity observations from the Sterling, Virginia WSR-88D and BWI TDWR radars, a network of 19 rain gages in the Dead Run watershed and drop spectra observations from a Joss-Waldvogel disdrometer. We also use analyses of these observations to examine the capability of measuring extreme rainfall from weather radar at spatial scales relevant to flash flooding
H11F-0373 0800h
Use of 2d Hydraulic Models to Predict Stage-Discharge Relationships in Urban Channels
Small urban watersheds (1-15 km$^{2}$) in the Baltimore metropolitan area with high percent impervious area and extensive storm sewer networks may have very short response time during thunderstorms, with lag to peak as short as 15 minutes for a drainage area of 9.1 km$^{2}$. Under these circumstances it is difficult to establish accurate stage-discharge relationships for stream gages; a field crew may not be able to reach the site in time to make a discharge measurement at high stage, and stage changes so rapidly that a complete measurement at a single stage often is not possible . In order to measure discharge accurately in small urban streams, it is necessary to develop stage-discharge relationships by supplementing direct discharge measurements with hydraulic modeling results for higher flows. In this study a 2d depth-averaged unsteady flow model (TELEMAC-2D; with k-epsilon turbulence closure as recommended by Wilson, et al, 2002) is used in combination with direct discharge measurements to develop stage-discharge rating curves at a series of monitoring sites in the Dead Run watershed. A preliminary working hypothesis suggests that the rating curves are not necessarily single-valued and sometimes exhibit looped or hysteretic behavior that is at least partly dependent on the shape and time base of the hydrograph. Sensitivity of the rating curve to other boundary conditions is also explored.
H11F-0374 0800h
Rapid-Response Monitoring of Flood Inundation in a Small Urban Watershed
Intense precipitation on July 7, 2004 from a multicell thunderstorm system (approximately 100-130 mm in 50-75 minutes) caused widespread flooding in the highly urbanized 14.3 km$^{2}$ Dead Run watershed, which drains the eastern suburbs of Baltimore. The Dead Run watershed is bisected by a pair of intersecting interstate highways and several other major traffic arteries, and land cover is predominantly commercial, industrial and residential. Reconstruction of flood peaks based on surveyed high-water marks indicates that this event exceeded the previous record set by Hurricane Agnes in 1972 at multiple locations upstream of the official USGS gage at Franklintown. Availability of high-resolution (~30 cm) orthorectified aerial photographs and 1-m lidar topography data allowed rapid deployment of student field crews during the week after this event to generate a flood-inundation map with surveyed high-water elevations for the entire drainage network downstream of the Baltimore Beltway (I-695) and for selected stream reaches upstream of the Beltway. Inundated areas were comparable to those mapped previously using FEMA guidelines as 100- and 500-year floodplain. Partial stage hydrographs recorded at three locations, supplemented by field observations of the time of peak, are used in conjunction with 2d hydraulic modeling analyses to reconstruct the spatial and temporal dynamics of this flood.
H11F-0375 0800h
Similarity Analysis of Subsurface Flow Response of Hillslopes With Complex Geometry
Recently, Troch et al (2003) introduced the hillslope-storage Boussinesq (hsB) equation to describe subsurface flow and saturation along complex hillslopes. The hsB equation can be linearized and further reduced to a diffusion-advection equation for hillslopes with constant bedrock slopes and exponential width functions. This paper presents a dimensional analysis of the latter equation in order to study the pure drainage flow response, which, once normalized by the flow volume, is defined as the characteristic response time distribution (CRTD). In the Laplace domain, an analytical expression for the discharge is obtained and used as moment generating function to derive the analytical expressions for the CRTD moments. These moments, in a dimensionless form, can be expressed as function of a subsurface flow similarity parameter, hereafter called the hillslope P\'eclet number, and a group of dimensionless numbers accounting for the initial condition effects. The analysis of their respective influences on the first four CRTD central moments shows that the first studied type of initial condition (uniform water table depth) has a strong impact on the dimensionless mean response time of the CRTD but negligible effect on the higher order moments, while the second studied type of initial condition (steady state water table profile) has a limited effect on all first four CRTD moments and hence, in this case, the hillslope P\'eclet number completely defines the subsurface flow similarity between hillslopes.
H11F-0376 0800h
A Radar Climatology of Extreme Rainfall in the Front Range of the Rocky Mountains
Analyses of the spatial and temporal distribution of extreme rainfall in the Arkansas River basin above Pueblo, Colorado are based on analyses of volume scan radar reflectivity observations from the Pueblo and Denver WSR-88D radars for the period 1995 - 2004. Climatological analyses of extreme rainfall are carried out both from an Eulerian perspective, in which the time-varying distribution of rainfall at fixed locations is examined, and a Lagrangian perspective, in which distributional aspects of rainfall are based on storm tracking algorithms. Of particular interest is the spatial heterogeneity of extreme rainfall in the complex terrain of the upper Arkansas River basin. Lagrangian analyses are used to characterize the spatially varying distribution of storm initiation, storm motion and storm structure. Analyses are motivated by problems of dam safety in which distributional properties of extreme rainfall are of most interest. Climatological analyses of extreme rainfall in the upper Arkansas River basin are examined relative to the spatial and temporal properties of two extreme rain events that occurred in June 1921 and June 1964. Radar climatology indicates a lack of spatial coherence in extreme events over the basin, with the upper basin rainfall climatology exhibiting pronounced contrasts with that of the lower basin.
H11F-0377 0800h
Columbia River Suspended Sediment Monitoring
For the past two springs we have monitored suspended particulate matter (SPM) in the tidal-fluvial part of the Columbia River, 86 km from the mouth. We have monitored SPM with a LISST-floc, which measures sediment volume concentration in 32 log spaces particle size bins from 8 to 1500 microns. Periodic site visits have included filter sampling to determine mass concentration and an estimate of representative fall velocity. A USGS station also located at the Beaver site supports an ADP (velocity and acoustic backscatter), water level gage, and turbidimeters. Comparison of LISST and turbidimeter gages illustrates the importance of grain size data information in sediment monitoring. In both 2003 and 2004 we captured minor winter high flow events. Both years also captured data from spring freshets resulting from melting of snows in the Columbia River Interior Sub-basin. However, 2003 included heavier spring rains whereas 2004 included ligher spring rains. In June 2004 the LISST-floc was deployed in cast mode in the Columbia River estuary allowing comparison of suspended sediment in the freshwater river with suspended sediment in the saline estuary. The complex sediment processes in the estuary noticeably alter riverine sediment input.
H11F-0378 0800h
Global change and drought severity in the Battle River Basin, Alberta
The Battle River basin is a prairie watershed with headwaters in the central Alberta Parkland region immediately east of the Rocky Mountain foothills. The watershed has low relief - mean slope of about 1.5% - typical for a prairie landscape. Most streamflow originates from spring snowmelt. In years with high snowmelt runoff, the channel wetlands are extensive and enhance runoff from summer showers. In years of low snowmelt runoff, the wetlands are of modest scale, and the rate of runoff from summer showers decline rapidly as the season advances and the wetlands shrink or disappear. Upland wetlands, also called sloughs or potholes, likely contribute very modest quantities of water to the regional groundwater system that interacts with the Battle River. The Battle has suffered a severe climatic and hydrologic drought since the year 2000. The objective herein is to define the relative severity of the drought in 2000-04 in the upper Battle River watershed. Dendrochronology data indicated the drought was one of the worst in the past several centuries. Frequency analyses indicated the summer low flow experienced in 2002 was stochastically a 1:217 year event. The average Palmer Drought Severity Index (PSDI) over the entire basin in July 2002 is at an historical extreme. Land use changes are likely adversely affecting runoff. Climate change is likely affecting hydrology, including timing and volumes of the spring peak flow and summer runoff. Water licenses have increased significantly over the past years and certainly contribute to the cumulative effects resulting in reduced streamflow, particularly in the summer months. Water authorities must re-examine the assumptions for engineering design and water allocation in the basin given the changing climate and hydrology regimes.
H11F-0379 0800h
Flood Inundation Models using Airborne Laser Altimetry (LIDAR) to Establish Significance of Spatial and Temporal Distribution of Indicators for Ordinary High Water Marks in Arid Southwestern Stream Systems
"Waters of the United States" (WoUS) are identified by use of physical features in the field to determine the location of the "Ordinary High Water Mark" (OHWM) and the limits of the Federal jurisdiction under the Clean Water Act (33 CFR 328.3). Arid fluvial systems that dominate the western landscape are critically important environments that provide valuable ecological benefits to the nation. These arid streams and rivers recognized as WoUS convey floodwaters and help ameliorate flood damage; maintain water quality and quantity; provide habitat for plants, aquatic organisms and wildlife, which determine the physical characteristics and biological productivity of downstream environments. Recent research efforts have identified a variety of field OWHM indicators useful for delineation purposes in the arid west. As part of that same ongoing effort, testing the reliability of the field OHWM indicators in identifying WoUS boundaries has provided insight to the distribution patterns of physical and biological features in response to a suite of discharges of varying magnitude and frequency. The objective of this research is to utilize 1-D HEC-RAS flood inundation models (2, 5, 10, 25, 50 and 100 year return intervals) for two intermittent stream channel reaches at different landscape positions in the Mojave Desert, California using highly accurate lidar topographic data and detailed field mapping results to test the reliability of the field OHWM features in identifying the WoUS boundary and to better understand the frequency of inundation necessary for creation and maintenance of the various field OHWM features. Our preliminary results show that 80-90 percent of the OHWM indicators are located within or near the active floodplain, and some are sorting along the bankfull channel. Surficial textural differences and vegetative cover patterns are sorting along the active floodplain boundaries while the distribution of other vegetative indicators within the stream channel reach are associated with distinct flood inundation levels. It has been previously noted that relationships between flood frequency and physical and biological responses, vegetation structure and species diversity of riparian communities exist. Although, current wetland delineation and evaluation methods for the arid west do not connect OHWM or other physical and biological features to flood frequency which are the over riding factor in assessing the WoUS functional levels of a watershed.
H11F-0380 0800h
Monitoring Sediment Transport, Stream Stage, and Salinity with Time Domain Reflectometry
Results are presented from an ongoing field investigation into the applicability of Time Domain Reflectometry (TDR) for remote, real-time monitoring of streambed dynamics, stream discharge, and water quality. A TDR based stream monitoring system involves propagation of a high frequency, low voltage electromagnetic pulse through waveguides installed riverbed sediments. Reflected signals (traces) from each sensor are analyzed to locate dielectric discontinuities resulting from air-water and water-sediment interfaces, as well as to evaluate the extent of signal attenuation due to the electrical conductivity of the media/water. Trace analysis is by way of a multi-section physical based model using the S11 scatter function and the Cole-Cole parameters for dielectric dispersion and loss (e.g., Feng et al., WRR 35(8), 1999). Application of this approach to data from laboratory experiments demonstrates that TDR can locate air-water and water-sediment interfaces to an accuracy of ±1.9 mm at a precision of ±0.4mm. Electrical conductivity of freestanding water above a sediment water interface is measured to ±8 percent of the actual conductivity at a precision of ±9 S/cm. Eight sensors have been installed in the Rio Grande at Albuquerque, New Mexico. Seven sensors capture riverbed dynamics while the eighth is installed adjacent to the riverbank to measure river stage. TDR measurements are compared to independent measures of stream stage, riverbed morphology, and water conductivity. A second monitoring site was established on the Paria River near Lees Ferry on the Colorado in northern Arizona where TDR measured stream stage and conductivity are collected. Stream stage data is compared with a float gauge and radar data. Results show that TDR accurately reproduces the independent measures of stream stage and conductivity.
H11F-0381 0800h
A Comparison of Drought Assessment by the Aggregate Drought Index (ADI) and the Standardized Precipitation Index (SPI)
The Aggregate Drought Index (ADI) is a new index for measuring the severity of drought conditions, and is based on principal components analysis of monthly hydrologic data (Keyantash and Dracup 2004). The Standardized Precipitation Index (SPI) is a widely-used drought index that assesses the severity of meteorological drought based on probabilistic interpretation of precipitation shortages. Both indices may be used to describe drought over multiple timescales. The commonalities and differences for these two drought assessment approaches are compared for two climate divisions in Oregon-representing moist and dry environments-for water years from 1976 to present.
H11F-0382 0800h
Potential Effects of Wildfire on Watershed Hydrologic Response: Sabino Creek Basin, Arizona
Wildfires and their hydrologic consequences, such as flash floods and mudslides, pose serious hazards in the southwestern United States. As a result of the present drought and decades of fire suppression, wildfires are occurring with greater frequency and intensity. Preservation or rehabilitation zones can be identified in a watershed to minimize the severity of secondary-order fire effects, such as erosion, increased flow peaks and landslides. Distributed hydrological models can be a useful tool to locate these zones. In this study, a distributed watershed model was used to evaluate the effects of pre- and post-fire land use scenarios on watershed hydrologic response in the Sabino Creek watershed north of Tucson, Arizona. During the summer of 2003, the Aspen fire burned in excess of 34 thousand hectares in the Santa Catalina Mountains, including a large part of the study basin. To model the watershed, field and laboratory measurements of soil permeability in burned and unburned areas were used, together with fifteen years of climatological data from NOAA, USGS and Pima County. To investigate the hydrologic effects of wildfire, model simulations using pre- and post-fire soil and vegetation parameters, in particular soil permeability and leaf area index, were compared to each other as well as to field observations.
H11F-0383 0800h
Ice Jams on the Little Missouri River, North Dakota and North Platte River, Nebraska
During the winter months, rivers in the north central United States have a phenomenon occurring, which is known as "ice jams". The initial melting of the river ice causes broken ice buildup, which acts as a quasi-dam restricting the natural flow. Ice jams severely impact ecosystems and are known to cause extensive damage to the channels, as well as man-made structures. The focus of this paper is on ice jams on the Little Missouri River in North Dakota and the North Platte River in Nebraska. Previous investigations done on the Lower Platte River valley, as well as the Missouri River basin, have shown that the primary cause of ice jams on these rivers is due to the spring thaw. The initial portion of the paper will discuss the pattern of ice jams on these rivers, as well as some mitigation strategies for control of these ice jams. The second section will deal with the modeling of ice jams on these river systems using HEC-RAS. This model will be comprised of both two and three-dimensional aspects of the rivers.
H11F-0384 0800h
Challenges of Artificial Recharge at the Chain of Lakes
A series of gravel quarry lakes, A through I (i.e. Chain of Lakes) in Alameda County, California are planned to convert to off-channel spreading lakes for artificial groundwater recharge. An operational plan is needed for the near-term improvements that would allow safe and efficient operations of Lake H and Lake I recently acquired for artificial recharge operations. Water source for the groundwater recharge comes from State Water Project (SWP) water releases at the South Bay Aqueduct turnout. The released water flows approximately nine miles in Arroyo Mocho Creek to the planned diversion facility. The recharge system includes multiple water delivery components and recharge components. Reliability of SWP water delivery is a water supply constraint to the recharge system. Hydraulic capacities of each delivery component and recharge capacities of each recharge component are physical constraints to the development of the operational plan. Policy issues identified in the Mitigated Negative Declaration which contains mitigation measures addressing potential impacts of fisheries and erosion are regulatory constraints to the operational plan development. Our approach that addresses technical challenges and policy issues in the development of the operational plan includes i) determination of lake recharge under observed conditions using water budget method; ii) development and calibration of a ground water flow model using MODFLOW; iii) estimation of lake recharge capacity for a range of lake levels using the calibrated ground water flow model; iv) analysis of clogging layer effects on recharge capacity; and v) development and application of operations models for the stream delivery system and the lake system.
H11F-0385 0800h
Vorticity, Stokes' Theorem and the Gauss's Theorem
Vorticity is a property of the flow of any fluid and moving fluids acquire properties that allow an engineer to describe that particular flow in greater detail. It is important to recognize that mere motion alone does not guarantee that the air or any fluid has vorticity. Vorticity is one of four important quantities that define the kinematic properties of any fluid flow. The Navier-Stokes equations are the foundation of fluid mechanics, and Stokes' theorem is used in nearly every branch of mechanics as well as electromagnetics. Stokes' Theorem also plays a vital role in many secondary theorems such as those pertaining to vorticity and circulation. However, the divergence theorem is a mathematical statement of the physical fact that, in the absence of the creation or destruction of matter, the density within a region of space can change only by having it flow into, or away from the region through its boundary. This is also known as Gauss's Theorem. It should also be noted that there are many useful extensions of Gauss's Theorem, including the extension to include surfaces of discontinuity in V. Mathematically expressed, Stokes' theorem can be expressed by considering a surface S having a bounding curve C. Here, V is any sufficiently smooth vector field defined on the surface and its bounding curve C. Integral (Surface) [(DEL X V)] . dS = Integral (Contour) [V . dx] In this paper, the author outlines and stresses the importance of studying and teaching these mathematical techniques while developing a course in Hydrology and Fluid Mechanics. References Arfken, G. "Gauss's Theorem." 1.11 in Mathematical Methods for Physicists, 3rd ed. Orlando, FL: Academic Press, pp. 57-61, 1985. Morse, P. M. and Feshbach, H. "Gauss's Theorem." In Methods of Theoretical Physics, Part I. New York: McGraw-Hill, pp. 37-38, 1953. Eric W. Weisstein. "Divergence Theorem." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/DivergenceTheorem.html