UM-1 :Tyson Weber ground water flow model

Abstract

The ground water in a basin is not at rest but is in a state of continuous movement. While the recharge components tend to rise the water table, the discharge components make the water table to go down. However, over a long period of time, the storage in aquifer would be tending to be a constant thus creating a state of dynamic equilibrium condition wherein the recharge components are counteracted by the discharge components. In most of the cases the fluctuations over a short period of time are significant, because they may affect other processes like the base flows into the river, the seepage from the canals. These effects may have influence on economic development of the region. As such, the study of water table fluctuations in the aquifer media under different stress conditions and understanding of the system are important which would facilitate to predict and if necessary to counteract the ill effects.

With the advent of fast computers the complex problems relating to the groundwater simulation studies could be solved with better accuracy using the numerical techniques like finite difference and finite element approximations. In this manual, one of the finite differences solution techniques viz, Tyson Weber Finite difference approximation for solving groundwater flow problems was discussed and mathematical model based on bi-seasonal time step discretization was discussed in detail. attempt has been made to indicate the various aspects of the Tyson-Weber Model. Both stead; state and transient solutions can be obtained using this mc el. All input data are automatically checked for consistency and completeness and proper messages are generated. For easy implementation and usage the program has been divided into 3 independent modules. The module GEOMF determines the horizontal and vertical flow factors, the ground level at the nodal points and nodal faces, and the polygonal areas from the input data. The recharge abstraction programme computes the various recharge and abstraction components for the discretized area.

The main programme receives the information developed by both GEOMF module and REFAC module and computes .he water levels at all the internal nodes in the study area The advantages of modular discretization of the programme have been presented. The terminology which has been used in the manual has been defined and hardware and software requirements are also presented. The various data and the format for the same are also presented. The calibration strategies and validation of the model with real data is incorporated. The limitation and intricacies of the model are discussed. An example with the sample input, sample output was also indicated to familiarise the reader for using the model.