Characterization of Water Movement Into and Through Soils During and Immediately After Rainstorms

The movement of water into and through soils in the unsaturated state is basic to many water resources problems including rainfall-runoff models, ground water recharge, irrigation, drainage, evapotranspiration and the movement of pollutants in soils. This study was conducted in an effort to determine if the flow equation based on Darcy\u27s Law and the continuity equation could be used to describe watershed infiltration and thus be incorporated into hydrologic models. The results of the study indicate that even on apparently uniform soils there is a great deal of variability in soil water properties. Handling this variability plus the difficulty of solving the flow equation led to the conclusion that a simpler approach to modelling watershed infiltration is needed. A simple infiltration model was developed and included in a rainfall-runoff model. Tests with the model indicate that it produces satisfactory estimates of monthly runoff from small, rural watersheds

Optimal Systems of Storm Water Detention Basins in Urban Areas

Flood retention basins are commonly used in urban areas to reduce the impact of urbanization on downstream flooding. When more than a few acres are developed, systems of retention basins are often required. A procedure has been developed whereby the optimum (least cost) system of basins can be determined to meet a given downstream flow requirement. The method considers several design options including basins on all subwatersheds, basins on only some of the subwatersheds, basins of various sizes and basins with various stage-discharge characteristics. The procedure has been developed in the form of a computer program to aid the designer in selecting the optimum system of stormwater retention basins. This report develops the methodology, presents the computer program and illustrates the use of the program

Evaluation of Detention Basins for Controlling Urban Runoff and Sedimentation

This report summarizes the work completed under the research project Evaluation of Dentention Basins for Controlling Urban Runoff and Sedimentation. The main project accomplishments were: (1) a demonstration of the desirability of considering systems of urban stormwater detention basins as opposed to individual basin design, (2) the development of a systems analysis approach for least cost selection of a system of dentention basins for meeting a preset hydrologic objective, (3) the development of a mathematical, computer-based simulation model of the performance of sediment retention basins, (4) partial verification of the sediment basin model and (5) the development of design recommendations for sediment basins based on simulations made with the sediment basin model

Supply and Demand in Water Planning: Streamflow Estimation and Conservational Water Pricing

Recent studies indicated the need for development of surface water supplies in Kentucky. Rising resource costs make economically efficient reservoir designs increasingly important. This study was undertaken to provide methods in water supply reservoir design that increase system benefits. Two major factors influencing reservoir design were studied: estimated future streamflow into the reservoir and demands placed on the reservoir. Standard reservoir sizing methods rely on historical streamflow data. This data is frequently limited and uncertainty in required storage estimates may result. To assess the reliability of a design, the use of mathematical models in simulation studies was proposed. Existing stochastic and parametric models of streamflow were reviewed and their limitations discussed. Parameters for the stochastic models must be estimated from historical streamflow data, and limited data produces unreliable estimates of the true values for these parameters. A streamflow record extended by a parametric model through simulation may provide more reliable estimates of the parameters in the stochastic streamflow model than the short historical record. A methodology was presented to evaluate the ability of a parametric model to improve the stochastic model parameter estimates in this manner. It was found that the parameter estimates of a stochastic model might be significantly improved by this process. A long historical record of rainfall may not be available to provide the necessary inputs to a parametric model. One method for providing these inputs is to model the daily rainfall process at the potential site. A modified Markov Chain model was proposed which used continuous distributions, rather than discrete transition probabilities, to represent the process when rainfall actually occurred. A two-parameter gamma distribution fit the Kentucky data. The model provided a good representation of the daily point rainfall process. 15-20 years of historical daily rainfall data were required to produce stable estimates of model parameters. The role of the demand function in reservoir design was examined. Projected demand is commonly assumed not to depend on the concurrent water rates. Data on rural residential water demand in Kentucky has indicated that a price-demand relationship does exist for this sector. The second part of the study was undertaken to see if benefits to a hypothetical community from water supply could be increased by utilizing price-demand information in reservoir design studies. Three pricing policies were examined and their effect on reservoir design determined. The first policy assumed no price-demand relationship, and demand was based on existing community usage with a low water rate. A price-demand relationship was assumed in the second policy, and the water rate was constant. The third policy assumed the price-demand relationship, and the price charged for water during each billing period was a non-linear function which increased as the amount of water in storage at the beginning of the period decreased. It was found that the use of the conservation pricing policies substantially reduced storage requirements while providing increased, demonstrable net benefits to the community. The conservation pricing policies substantially lowered the average price paid for water. The effect of uncertainty in consumer response to changes in price was studied by using a probabilitistic price-demand relationship. This uncertainty did not significantly reduce the effectiveness of the conservation policy. It was concluded that demand management by the use of a proper pricing policy could significantly increase water supply benefits to a community

Modeling Soil Water Movement into Plant Roots

Mathematical model was developed which describes uptake of water by plant roots as a function of leaf and soil water potentials. The model was used to estimate transpiration from corn grown in a controlled environment under soil drying conditions. The model predicted daily transpiration quite well for the period modeled

Explaining two circumnuclear star forming rings in NGC5248

The distribution of gas in the central kiloparsec of a galaxy has a dynamically rapid evolution. Nonaxisymmetries in the gravitational potential of the galactic disk, such as a large scale stellar bar or spiral, can lead to significant radial motion of gaseous material from larger radii to the central region. The large influx of gas and the subsequent star formation keep the central region constantly changing. However, the ability of gas to reach the nucleus proper to fuel an AGN phase is not guaranteed. Gas inflow can be halted at a circumnuclear star forming ring several hundred parsec away. The nearby galaxy NGC5248 is especially interesting in this sense since it is said to host 2 circumnuclear star forming rings at 100pc and 370pc from its quiescent nucleus. Here we present new subarcsecond PdBI+30m CO(2-1) emission line observations of the central region. For the first time the molecular gas distribution at the smallest stellar ring is resolved into a gas ring, consistent with the presence of a quiescent nucleus. However, the molecular gas shows no ring structure at the larger ring. We combine analyses of the gaseous and stellar content in the central kiloparsec of this galaxy to understand the gas distribution and dynamics of this star forming central region. We discuss the probability of two scenarios leading to the current observations, given our full understanding of this system, and discuss whether there are really two circumnuclear star forming rings in this galaxy.Comment: Accepted for publication in A&A, 14pages + long tabl

Simulation of the Sedimentology of Sediment Detention Basins

Sediment detention basins are a widely used means of controlling downstream sediment pollution resulting from stripmining and construction activities. A mathematical model for describing the sedimentation characteristics of detention basins has been developed. This model requires as inputs the inflow hydrograph, inflow sediment graph, sediment particle size distribution, detention basin stage-area relationship and detention basin stage-discharge relationship. Based on this information the model routes the water and sediment through the basin. In this routing process the outflow sediment concentration graph, the pattern of sediment deposition in the basin and the sediment trapping efficiency are estimated. Comparison of predicted results with measured sediment basin performance indicates the model accurately represents the sedimentation process in detention basins. This report details the model, illustrates its use in design, explains how to process the model on a digital computer and presents a program listing of the model

Rural Residential Water Demand in Kentucky: An Econometric and Simulation Analysis

This study proposed that demand management through pricing policies can be used in conjunction with supply management to solve water supply problems in Kentucky. Economic principles were shown to apply to rural residential water use. From the economic model, a hyperbolic demand function was theorized. The mathematical form of this function used quantity of water as a function of price, income, value of residence, evaporation, and persons per residence. This function was estimated using ordinary least squares regression. A log-linear model was found to be a satisfactory representation of the demand function. Price was the only independent variable which was significant and had an elasticity of (-.92). As an application of pricing to demand management, the estimated regression equation was used in a simulation analysis. The simulation was used to determine the reservoir capacity necessary to supply the needs of 4,000 households given three different price levels for water. Reservoir size was determined by simulating reservoir size as a function of outflow as estimated from the demand function plus an assumed low flow rate and inflow from the Thomas-Fiering Model. This technique illustrated that price does affect the quantity of water demanded which in turn effects reservoir capacity requirements