Rainfall is the most ...
Published by Prem Baboo, Researcher at www.researchGate.net
Rainfall is the most important source of ground water recharge in the country. The most commonly used methods for estimation of natural ground water recharge in India include empirical methods, ground water level fluctuation method and the ground water balance method.Groundwater was the major source for irrigation prior to the introduction of canal irrigation system. Water contained in the voids of the geologic materials that comprise the crust of the earth is the groundwater. It exists at a pressure greater than or equal to atmospheric pressure. The experimental and mathematical methods required for analyses are distinctly different as it is exploited and used in human affairs in different ways. The important hydrogeological parameters such as porosity and hydraulic conductivity of the geologic stratum determine the performance of the aquifer. Added to this, an important factor is the length of data considered for predicting the groundwater potential. Thus, with adequate length of the database, the prediction of any derived model will reproduce the statistical properties. Otherwise, it is difficult to predict the regional groundwater flow conditions, subject to measurable hydrological, hydrogeological and meteorological variables in nature. As it is largely uncertain in nature, this cannot be left in isolationDifferent methods were proposed and many authors reviewed several applications on this problem. Rushton and Rathod (1985) have determined the velocity components from information about the groundwater-head distribution, groundwater potential, confined and unconfined aquifers; time-variant behaviour of aquifer and hydraulic conductivity. Mathematical models have been developed by Serrano and Unny (1987) as an innovative approach to the solution of groundwater forecasting problems considering the uncertainty generated by the use of data subject to environmental fluctuations and measurement errors. They have described in detail the development, solution and validation of two mathematical models describing groundwater potential at the Twin lake aquifer. Sondhi et.al. (1989) have determined the available additional groundwater potential and its distribution in the project area; estimation of groundwater recharge from the water conveyance and distribution system and the annual water balance of the project; 'recharge distribution coefficients' are done using digital simulation models. Chiew and McMahon (1990) estimated groundwater recharge using surface watershed modeling approach for both irrigated and non-irrigated areas. In all the above cases, they have not seen which time period will give appropriate prediction over the recharge value of a basin area. Uma and Kehinde (1992) described the analysis of the baseflow characteristics of numerous small basins to estimate the groundwater in the basins. Boonstra and Bhutta (1996) have worked on determination of seasonal net recharge considering temporal and areal recharge variations, geometry of aquifer system, historical water table elevations, drainage design and waterlogged areas, and developed numerical models for monsoon estimates, water-balance, and return period. A similar attempt is made here for estimating the ground water recharge potential of a river basin.
The commonly used method for estimating groundwater storage available annually is based on
Q = (Area) x (Depth of fluctuation in Groundwater Table) x (Specific Yield) (1)
In the above equation, the depth of fluctuation in groundwater table or the drop in groundwater table has to be calculated by taking the duration over which the fluctuation occurs