UNCERTAINTY BASED OPERATION OF LARGE SCALE RESERVOIR SYSTEMS: DEZ AND KAROON EXPERIENCE1

ABSTRACT: Reservoir operation involves a complex set of human decisions depending upon hydrologic conditions in the supply network including watersheds, lakes, transfer tunnels, and rivers. Water releases from reservoirs are adjusted in an attempt to provide a balanced response to different demands. When a system involves more than one reservoir, computational burdens have been a major obstacle in incorporating uncertainties and variations in supply and demand. A new generation of stochastic dynamic programming was developed in the 1980s and 1990s to incorporate the forecast and demand uncertainties. The Bayesian Stochastic Dynamic Programming (BSDP) model and its extension, Demand Driven Stochastic Dynamic Programming (DDSP) model, are among those models. Recently, a Fuzzy Stochastic Dynamic Programming model (FSDP) also was developed for a single reservoir to model the errors associated with discretizing the variables using fuzzy set theory. In this study the DDSP and the FSDP models were extended and simplified for a complex system of Dez and Karoon reservoirs in the southwestern part of Iran. The simplified models are called Condensed Demand Driven Stochastic Programming (CDDSP) and Condensed Fuzzy Stochastic Dynamic Programming (CFSDP). The optimal operating policies developed by the CDDSP and the CFSDP models were simulated in a classical model and a fuzzy simulation model, respectively. The case study was used to demonstrate the advantages of implementing the proposed algorithm, and the results show the significant value of the proposed fuzzy based algorithm.     

HISTORICAL EVOLUTION OF FLOODING DAMAGE ON A USA/QUEBEC RIVER BASIN1

ABSTRACT: There is a general belief in the public eye that extreme events such as floods are becoming more and more common. This paper explores this hypothesis by examining the historical evolution of annual expected flooding damage on the Chateauguay River Basin, located at the border between the United States and the province of Quebec, Canada. A database of basin land use was constructed for the years 1930 and 1995 to assess anthropogenic changes and their impact on the basin's hydrology. The progressive modification of the likelihood of a flooding event over the same period was then investigated using homogeneity and statistical tests on available hydrometric data. The evolution of the annual expected flooding damage was then evaluated using a coupled hydrologic/hydraulic simulator linked to a damage analysis model. The simulator and model were used to estimate flooding damage over a wide range of flooding return periods, for conditions prevailing in 1963 and 1995. Results of the analysis reveal the absence of any increasing or decreasing trend in the historical occurrence of flooding events. However, a general increase in the annual expected flooding damage was observed for all studied river sections. This increase is linked to an historical increase in damages for a given flooding event, and is the result of unbridled construction and development within the flood zone. To assess for future trends, this study also examined the potential impacts linked to the anticipated global warming. Results indicate that a significant increase in seasonal flooding events and annual expected flooding damage is possible over the next century. In fact, what is now considered a 100‐year flooding event for the summer/fall season could become a ten‐year event by the end of this century. This shows that potential future impacts linked to climate change should be considered now by engineers, land planners, and decision makers. This is especially critical if a design return period is part of the decision making process.     

AN ECONOMIC ANALYSIS OF ALTERNATIVE WATER USE STRATEGIES AT CATCHMENT LEVEL TAKING INTO ACCOUNT AN INSTREAM FLOW REQUIREMENT1

ABSTRACT: A mathematical model of agricultural water use and a hydrological and economic simulation model were linked to quantify the economic and hydrological impact of deficit irrigation, increased water application efficiency, and farm storage dams when maintaining an IFR (instream flow requirement) under stochastic water supply conditions. The main finding was that a water conservation policy aimed at reducing the amount of water withdrawn from the river could bring more pressure to bear on stream flow. Water can only be saved if consumptive use is reduced. Increased water application efficiency is detrimental to other users as a result of reduced return flow. The economic cost of maintaining a specific IFR increases with the use of all three strategies as the probability of maintaining the IFR increases. Because of the control that can be exercised over the supply of water, a farm storage dam is the best strategy for minimizing the costs for irrigators. The interaction between water legislation, water policy administration, technology, hydrology, and human value systems necessitates an integrated approach to facilitate water management at catchment level and to formulate policies that will be in the interest of society.     

ASSESSING CHANGES IN WATERSHED FLOW REGIMES WITH SPATIALLY EXPLICIT HYDRAULIC MODELS1

ABSTRACT: Urbanization, farming, and other watershed activities can significantly alter storm hydrographs and sediment erosion rates within a watershed. These changes routinely cause severe economic and ecological problems manifested in the form of increased flooding and significant changes in channel morphology. As the activities within a watershed influence the hydrologic, hydraulic, and ecological conditions within a river, interdisciplinary approaches to predict and assess the impacts that different land uses have on streams need to be developed. An important component of this process is ascertaining how hydrologic changes induced by specific watershed activities will affect hydraulic conditions and the accompanying flood levels, sediment transport rates, and habitat conditions within a stream. A conceptual model for using spatially explicit (two‐dimensional) hydraulic models to help evaluate the impacts that changes in flow regime might have on a river is presented. This framework proposes that reproducing and quantifying flow complexity allows one to compare the hydraulic conditions within urban, urbanizing, and non‐urban streams in a more biologically and economically meaningful way. The justification, advantage, and need for such a method is argued through the results of one‐ and two‐dimensional hydraulic model studies. The implementation of this methodology in watershed urbanization studies is described.     

MODELING THE HYDROCHEMISTRY OF THE CANNONSVILLE WATERSHED WITH GENERALIZED WATERSHED LOADING FUNCTIONS (GWLF)1

ABSTRACT: A previous modeling study used the Generalized Watershed Loading Functions (GWLF) model to simulate stream‐flow, and nutrient and sediment loads to Cannonsville Reservoir from the West Branch Delaware River (WBDR). We made several model revisions, calibrated key parameters, and tested the original GWLF model and a revised GWLF model using more recent data. Model revisions included: addition of unsaturated leakage between unsaturated and saturated subsurface reservoirs; revised timing of sediment export; inclusion of urban sediments and dissolved nutrients; tracking of particulate nutrients from point sources; and revised timing of septic system loads. The revision of sediment yield timing resulted in significant improvements in monthly sediment and particulate phosphorus predictions as compared to the original model. Addition of unsaturated leakage improved hydrologic predictions during low flow months. The other model changes improve realism without adding significant model complexity or data requirements. Goodness of fit of revised model predictions versus stream measurements, as measured by the Nash‐Sutcliff coefficient of model efficiency, exceeded 0.8 for streamflow‐0.7 for sediment yield and dissolved nitrogen (N) and 0.6 for particulate and dissolved phosphorus (P). The revised GWLF model, with limited calibration, provides reasonable estimates of monthly streamflow, and nutrient and sediment loads in the Cannonsville watershed.     

A STRIP MODEL APPROACH TO PARAMETERIZE A COUPLED GREEN‐AMPT KINEMATIC WAVE MODEL1

ABSTRACT: Infiltration processes at the plot scale are often described and modeled using a single effective hydraulic conductivity (Kg) value. This can lead to errors in runoff and erosion prediction. An integrated field measurement and modeling study was conducted to evaluate: (1) the relationship among rainfall intensity, spatially variable soil and vegetation characteristics, and infiltration processes; and (2) how this relationship could be modeled using Green and Ampt and a spatially distributed hydrologic model. Experiments were conducted using a newly developed variable intensity rainfall simulator on 2 m by 6 m plots in a rangeland watershed in southeastern Arizona. Rainfall application rates varied between 50 and 200 mm/hr. Results of the rainfall simulator experiments showed that the observed hydrologic response changed with changes in rainfall intensity and that the response varied with antecedent moisture condition. A distributed process based hydrologic simulation model was used to model the plots at different levels of hydrologic complexity. The measurement and simulation model results show that the rainfall runoff relationship cannot be accurately described or modeled using a single Kg value at the plot scale. Multi‐plane model configurations with infiltration parameters based on soil and plot characteristics resulted in a significant improvement over single‐plane configurations.     

CALIBRATION OF STORM LOADS IN THE SOUTH PRONG WATERSHED,FLORIDA, USING BASINS/HSPF1

ABSTRACT: The South Prong watershed is a major tributary system of the Sebastian River and adjacent Indian River Lagoon. Continued urbanization of the Sebastian River drainage basin and other watersheds of the Indian River Lagoon is expected to increase runoff and nonpoint source pollutant loads. The St. Johns River Water Management District developed watershed simulation models to estimate potential impacts on the ecological systems of receiving waters and to assist planners in devising strategies to prevent further degradation of water resources. In the South Prong system, a storm water sampling program was carried out to calibrate the water quality components of the watershed model for total suspended solids (TSS), total phosphorous (TP), and total nitrogen (TN). During the period of May to November 1999, water quality and flow data were collected at three locations within the watershed. Two of the sampling stations were located at the downstream end of major watercourses. The third station was located at the watershed outlet. Five storm events were sampled and measured at each station. Sampling was conducted at appropriate intervals to represent the rising limb, peak, and recession limb of each storm event. The simulations were handled by HSPF (Hydrologic Simulation Program‐Fortran). Results include calibration of the hydrology and calibration of the individual storm loads. The hydrologic calibration was continuous over the period 1994 through 1999. Simulated storm runoff, storm loads, and event mean concentrations were compared with their corresponding observed values. The hydrologic calibration showed good results. The outcome of the individual storm calibrations was mixed. Overall, however, the simulated storm loads agreed reasonably well with measured loads for a majority of the storms.     

DEVELOPMENT AND APPLICATION OF A MODFLOW PREPROCESSOR USING PERCOLATION THEORY FOR FRACTURED MEDIA1

ABSTRACT: The discrete heterogeneity of fracture distribution and hydraulic discontinuity are the primary difficulties in the modeling of flow in fractured media. The equivalent porous medium (EPM) approach, however, which has been frequently applied to simulate flow in fractured media due to its ease of use, ignores this. This practice results in some severe limitations such as hydraulic head averaging and an inability to handle preferred fluid pathways. The PMF package (a Preprocessor to MODFLOW for Fractured media) was developed employing percolation theory to address these limitations and to utilize the simplicity of the EPM approach at the same time. This preprocessor was applied to a fractured rock aquifer around Cranberry Lake in northern New Jersey. The calibration using hydraulic head observations, validation using water balance, and evaluation using residuals show that the model generated by the PMF package can provide a superior simulation of ground water flow to the EPM approach.     

Source resolution and risk apportionment to augment the Bubble Policy: Application to a steel plant “bubble”

Source resolution and risk apportionment of emission source categories for risk reduction purposes can be used to enhance the Bubble Policy of the Clean Air Act. This is performed by incorporating receptor modeling techniques of factor analysis and chemical mass balances to assess noncarcinogenic and carcinogenic inhalation risks to a target population for certain pollutants coming from major emission source categories in a steel plant air shed. Source resolution, using factor analysis, statistically interprets a “source” from ambient data. By subsequently quantifying risks from identified metal emission sources using chemical mass balances and risk apportionment, a total additive risk from main source contributors in the steel plant is estimated. From this methodology, the Bubble Policy can be enhanced by targeting only main risk sources or by “risk-trading” with minor impact sources to reduce the total risk (if deemed significant) without arbitrarily reducing risk for all sources in an industrial source complex’s “bubble.”     

洞庭湖区水文气象灾害及其对渔业生产的影响

本文通过大量而系统的资料,阐述了越来越严重的水文气象灾害,导致洞庭湖湖面萎缩、湖容减小、洪涝频仍、气温年差增大,湖泊效应衰退,使鱼类生态系统受到破坏。并针对上述情况提出了防治对策。