GROUND WATER SIMULATION OF VARUNA BASIN BY RESISTANCE-CAPACITANCE NETWORK (ANALOG MODEL)

Abstract

Electric analog model is a valuable tool for the manag rent of ground water basins. Analog models can play an important role in the forecast of the consequences of developing nonhamogencous aquifers having boundark5 avid a Vac'(ty of irregularnhoaad and discharge controls. Analog models are simplo, versatile and of moderate cost. The use of analog model enables ground water deveiop-mont schemes to be tested rapidly and accurately thus permitting the apparai-sal of the relative merits of alternative choices of develop ent. The electric analog model sy stein consists of an analog model and wave form functional Generator arse bly and oscilloscope. The analog model is based on the similarity of laws governing flow of current in an olectri-. cal natuork and flow of water in an aquifer. The electric network is con only used is Resistance-Capacitance flettLoI3C. Resistors are inversely proportional to the hydraulic conductivity of the aquifer and capacitors store electric energy in a manner analogous to the storage of water in an aquifer. The behaviour of the electric network is described by the equation that has the sane form as the finite difference equation for nonsteady state, two or three dimensional flow of ground water. Electrical units (Voitages, Coloulun. b, ompheres and seconds) and corresponding hydr. ,ulic units (cubic metre, cubic metre per day and months) are connected by 4 scale factors. In the present study the analogy has been established for tho Varuna basin - a basin in the State of Uttar Pradesh, India. The available pump test data have been analysed to evaluate the formation constants of the aquifer and thus the scale factors for the analog model have been derived using formation constants uniform over the basin. The area of the basin has been divided into polygonal subareas with respect to rain-gauge stations. The weighted monthly rainfall recharges (30 percent & 35 percent of total monthly rainfalls in each node) and withdrawls from the aquifer has been calculated monthly considering with respect to gross water requirements by the different crops both in tubcuaU and canal commands. The seepage losses in the canal command has been taken as recharge monthly into the aquifer. Thus the monthly not recharges and withdrawls have been worked opt for each nodes. The available water level elevation records have been simulated in the form of direct current voltage on the model by stabilized power supply. The not rochargp and withdrawls have been given as input to each nodes in wave form and the response of the aquieer for each node has been obtained. The waveform functional generator forces equal electrical energy in proper time phase into the analog model and energy levels within the Resistor-Cq3acitaor network at each nodes has been measured. Oscilloscope traces i. e. Time-Voltage graph are analogous to water level change in time with the change in discharge or head. A catalog of Time-Voltage graphs provide data for the construction of a series of water level change maps.